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4,838 Posts
Discussion Starter #62
No kidding. But as slow as my typing is, it is still much faster to correct all those errors.

Sonnie, a question: The Montis do NOT have a bottom port, right? I was pretty sure I noticed that. The Summit X has dual woofers, the Ethos has a passive radiator, the Montis apears to be a simple sealed cabinet, but they don't say. Just wanted to be sure.

4,838 Posts
Discussion Starter #65
The Official $3,000 Speaker Evaluation / Home Audition Event


IT IS HERE! We are in the midst of the Home Theater Shack $3,000 Speaker Evaluation event, as I write this. Six pairs of speakers are on the premises, and over the next two days, Feb. 21 and 22, we will hear a lot of great tunes on them. There will be lots to report.

This is not a shootout. Each speaker will be set up for its best sound in this room and evaluated on its own merits.

For now, this post (#1) will be used as the summary post and will be updated through the weekend and beyond. Check back often - we will tell you ih later posts when this summary has grown.

The Speakers:
The Room:

Cedar Creek Cinema/Two-Channel Room, Luverne, Alabama. The most recent change to the room is that the equipment cabinet which used to occupy most of the space below the cinema screen has been removed. We deemed that removing the cabinet would improve the soundstage and imaging achieved. The room is lightly treated

The Evaluators:

Joe Alexander, Madison, Wisconsin. Joe is an avid audiophile and staff writer for Home Theater Shack.
Leonard Caillouet, Gainsville, Florida. Leonard has installed and set up speakers professionally for much of his life. He is a Moderator and Administrator and one of the chief technical gurus for Home Theater Shack.
Wayne Myers, Lincoln, Nebraska. A musician and lover of great sound, Wayne reviews speakers and headphones for Home Theater Shack.

Evaluation Tracks

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Associated Equipment
  • OPPO BDP-105 Universal Player - We will be using the 105 as the source for this evaluation. All of the tracks used during this evaluation event were extracted using either dBPowerAmp or Exact Audio Copy (EAC) from the original CDs, and were written to a USB flash drive and accessed for playback via the 5509's front-panel USB port. We appreciate OPPO being a sponsor here at HTS.
  • Onkyo PR-SC5509 9.2-Channel Network A/V Preamplifier - Our preamp/processor for the event: Onkyos' 5509. It is a highly capable processor and very well regarded as one of the top preamp processors available. We decided in this speaker listening event to include a brief evaluation for each speaker pair with Audyssey MultEQ engaged to see how it affects the soundstage and image clarity and "evens out" the room's influence on frequency response. The 5509, with MuiltEQ XT32 capability, made this a breeze. Of course, its 192kHz/32bit Burr-Brown DACs and specs like 0.05% total noise plus distortion (20 Hz–20 kHz, Half power) ensure it to remain completely transparent. We appreciate Onkyo being a sponsor here at HTS.
  • XPR-5 Five-Channel Reference Power Amplifier - The XPR-5 is a fully discrete, dual differential, high current, short signal path Class A/B amplifier with a Class-H power supply. The power supply rails are modulated to stay a minimum number of volts above the amplifier's output. This yields an efficient design that will stay cool while driving a pair of 8 Ohm speakers to 500 W or a pair of 4 Ohm speakers to 750 W. Having lots of clean power available is important when evaluating two-channel speakers. With the XPR-5 there is never a question or concern about being able to drive the speakers under test cleanly and reliably. Thanks to Emotiva for being a sponsor at HTS.
It has been invaluable to have the three sets of ears and listening perspectives together for these events. One evaluator will hear a certain quality and be ready to rave about it, making note of some other "minor factor," and another evaluator will have found that "minor factor" more like a showstopper, adding in his notes only a mention of what the first evaluator was crazy about. All in all, our perspectives came to rest with a great deal of consensus, but the contrasting views will no doubt stand out in our final write-ups.

back wall / soundstage

test seq

4,838 Posts
Discussion Starter #66
miniDSP DDRC-22D Dirac Live® 24/96 Room Correction Audio Processor Review

miniDSP Website
Available Direct From miniDSP

by Wayne Myers


The recently introduced DDRC-22D, DDRC-22A, and just announced DDRC-22DA are miniDSP's entries into the room correction market making use of Dirac Live room correction technology. The Dirac Live technology has been available for PC- and Mac-based systems for years from Dirac Research, founded in 2001. The technology is also licensed for use in cars, smart phones, and other audio products. It is a thoroughly implemented and robust technology which uses mixed-mode filters, making time and impulse response correction possible. The miniDSP entries are two channel models, standalone products which can be inserted in a home or professional system at various points in the signal chain to implement room correction. miniDSP is a Hong Kong based company specializing in digital signal processing products for audio applications.

Room Correction Technology

Mention digital room correction (DRC) in the presence of a group of serious audio hobbyists, and you are sure to get a lively discussion started. Arguments will range from "It doesn't work," or "It is always a bad idea," at one extreme to "It performs magical transformations" at the other. The more reasonable middle ground is that, applied judiciously with proper speaker and room preparation where possible, and with attention to detail in the calibration stage, DRC will often provide a significant improvement to the listening experience.

Note: There is a freeware, command-line-driven software product called Digital Room Correction, or DRC. For our purposes, we will be using "DRC" to talk about room correction in general.

The basic idea is that imperfections in loudspeaker design combined with real-world acoustical challenges in the listening room lead to a less-than-optimal listening experience for many, if not most, listeners. DRC attempts to compensate for and correct those imperfections to make the listening experience as close to perfect as possible. Bear in mind that even the definition of "perfect" in this situation is arguable. A calibrated measurement microphone is used to analyze a test signal at various positions around the listening position, then the resulting data is analyzed using some proprietary process, and a set of correction filters is generated to be placed in the signaling path as pre-compensation to correct for those speaker and acoustical imperfections.

Some DRC implementations focus on the frequencies below 200 Hz and leave the higher frequencies which are responsible for the characteristic sound of the speakers untouched, or relatively so. Some implementations purposely do not attempt time correction, while others purposely do; there are arguments supporting either approach. Some allow the user to select the amount or severity of correction applied. Most advanced, or professional, implementations allow the user to apply a desired target curve to the resulting filter set. An ideal approach will never be agreed upon.

The result? With some preparation and care, and a little experience, most users get real and worthwhile improvement quite easily. Those last two words are key, the reason people buy and use DRC products is to achieve big improvement with minimal fuss. A lot of engineering goes into making those products as easy to use as possible and as foolproof as possible. Proper preparation and care, the details of which are beyond the scope of this review, usually involve dealing with acoustical matters and careful speaker setup.

The Dirac Live approach to DRC involves frequency and time correction, using mixed-mode filters to attempt re-creation of the original impulse response of the delivered signal. The Dirac Live team has been at this for some time, and their product is mature and well proven, with many fans and adherents.


The DDRC-22D which I received for evaluation came boxed with a power supply, a UMIK-1 calibrated microphone with cable and accessories for room analysis, a nifty collapsible mic stand, two 6-foot long Toslink cables, a USB cable for connecting the DDRC-22D to a PC running the Dirac Live software (only necessary during calibration), and a pair of rack-mount ears. All software is downloaded from the miniDSP web site.

The DDRC-22D unit is a sturdily built metal chassis and is compact enough to easily find a place in a typical equipment rack or on a shelf. The single control knob on the front is a little exposed, not unusual for gear of this type. Also on the front panel are indicators for active input, Dirac Live active/bypassed, and indicators for which of the four downloaded filter sets is active. I would also have liked to see a readout for gain.

The control knob gives front-panel access to volume, input selection, and filter set selection, but not the active/bypassed selection, which I ended up wishing for during the evaluation process. All functions can be accessed via popular programmable remotes, and a utility is included to help with the remote learning process.

The rear panel has inputs and outputs, in this case Toslink, SPDIF digital coax, and AES-EBU on Neutrik 3pin XLR. This evaluation made use of the Toslink and SPDIF ins and outs.

As indicated , the unit has rewriteable memory to accommodate four stereo filter sets. When connected to the host PC by way of USB, with the Dirac Live software active, the filter set can be selected from the PC and made active or bypassed.

The Dirac Live software makes use of an impressive and functional user interface that did just about everything I could imagine wanting it to do. The user can retake any of the individual measurements of a measurement set, create/save/load/apply custom target curves, save and load measurement projects and, of course, determine which filter sets are installed in which of the four hardware memory locations in the DDRC-22D unit. The application is set to work only with the supplied UMIK-1 measurement mic; there is no option to use another type of measurement microphone.



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Associated Review Equipment
  • Music Server: foobar2000, Yohng VST Wrapper, Reaper ReaPlug VST Plugins, Phenom II x6 1055T, 8 GB memory
  • M-Audio FireWire 410 Audio Interface (TOSlink out)
  • 4x2 Remote Control Digital Optical TOSlink Audio Fiber Optic Selector/Splitter by Specialty Audio Video
  • Onkyo TX-SR705 Receiver
  • Crown Xs500 Power Amp
  • OSD Audio ATM-7 Digital 7-Zone Dual Source Speaker Selector with Remote Control
  • Martin Logan ESL Speakers
  • Home Theater Direct Level Three Towers
  • NHT Model 5 2-Way Bookshelf Speakers
  • Polk PSW10 Subwoofer, used with the NHT Model 5 Bookshelf Speakers
  • Beyerdynamic MM-1 Measurement Microphone
  • Roland Quad Capture Audio Interface

Evaluation Approach

The Dirac Live DDRC-22D was used in various combinations of the following situations:
  • Three different sets of stereo speakers, one with a subwoofer.
  • Two different target curves.
  • Two different mic setup patterns, "my way" (1 analysis point) and "by the book" (9 analysis points).
  • Comparison to Audyssey MultEQ XT.
  • Comparison to a hand-tuned room correction example.
Having played a bit with mic setup patterns for DRC implementations like Audyssey MultEQ (XT and XT32), and with listening position measurements in general, I have settled on a simplified measurement approach for my own use. It is effective, accurate, and quick to use. This is used in the "my way" (1-point) measurement approach as a reference.

The back of the listening chair, a recliner with a flat back which extends to top-of-head level, is covered with a thick, plushy blanket which remains there during measurements and listening to reduce reflections from the chair back. Soundstage and image clarity are improved during listening. When measuring, the measurement mic hangs by its cable at the center-of-head position, a couple of inches in front of the blanket. But even a soft blanket is slightly reflective, so a rolled-up hand towel is placed under the blanket so that it bulges out just far enough to barely touch the microphone tip. Voila, no reflection, and the frequency response in the area of the listener's head varies very little. A single measurement is taken, which is very smooth, no peaks or dips from reflections, and that is it. Listening tests confirm that the measurement result, correction filters, and the listening result all track beautifully.

Note: Having the UMIK-1 hanging by its cord for measurements will introduce some measurement error, the mic being 90 degrees off its reference axis and reading 1 to 2 dB low at 9 kHz for a typical UMIK-1. This would lead to extra boost at 9 kHz in the correction filter set. My target curve has enough loss at that frequency that the brightness is kept in control.

This technique - "my way" (1-point) - was used for a reference with each of the three Dirac Live speaker setups. Of course, Dirac Live setup was also completed "by the book," and most listening was done with this filter set. Results of both approaches are included in the following analysis.

Ease of Operation

Software and hardware setup were very straightforward. The online documentation covers this all in detail. My evaluation unit required a slightly different approach, but instructions had been written out in an email and when I had questions or a minor problem along the way, support via email was close to instantaneous.

Getting all of the pieces of a complex audio system to work together, especially in the digital realm, can sometimes be a little daunting. This is no reflection on the DDRC-22D or the Dirac Live software at all, simply a reality of the audio world. In my case, I ran the output of the DDRC-22D through the digital input of another audio interface and had to get the audio interface to sync to the 96 kHz output rate of the DDRC-22D. This should not be a problem with most DACs or AVRs which would normally follow the DDRC-22D in a typical setup.

I had the Direct Live software running concurrently with Room EQ Wizard, foobar2000, and Reaper in various combinations on the same laptop, and all behaved very nicely together, not always the case with audio software. To me this is a sign of a mature and carefully crafted product in the Dirac Live software.

I was very pleased with the software interface. It was extremely intuitive, well laid out, easy to follow without having to refer to documentation. At the appropriate stage, it includes a 3-D diagram of the mic pattern to be used for the analysis measurements, from three different perspectives.

Each of the nine analysis measurements can be deleted and retaken if desired. The order in which the measurements are taken is fixed. Actually, any number of measurement points from one to nine may be used, and only the absolute position of the first is critical, so the adventuresome user can play with the analysis mic pattern at will. An on-screen representation of the three sweeps taken for each measurement allows the user to see any major anomalies or noise interference.

Once the analysis sweeps are completed, the user can either use the default target curve or create or import her/his own. Target curve creation with the Dirac Live user interface is mouse click easy. Double click to add a node, or as many as you wish, to the curve and drag it where you want it. It is that simple. Target curves can be saved and recalled at will, so there is no limit to the number one may work with, although most experienced room tuners rely on two or three at most.

A project, including all of the measurement data, mic calibration curve, and target curve, can also be saved for later reuse. With a single click, the user applies a target curve to the analyzed and averaged input data, and a filter set is generated. The expected response is shown along with the input data and target curve. Here you can see the averaged left & right analyzed signals, the target curve, and the expected result curve. An Impulse Response view can also be selected.

The filter set can then be drag-and-drop loaded into one of the four memory slots in the DDRC-22D. At that point, one is ready to hear the corrected result.

Analysis Mic Patterns

The Dirac Live analysis software allows for up to nine measurement mic positions for an analysis data set.

The first measurement position is special. The Dirac Live software uses this first measurement to determine critical timing and distance information. It must be located where the center of the listener's head would be located at the Primary Listening Position (PLP). The other eight measurement positions should, in my experience, form a pattern with left/right symmetry around that first central point. They tell the Dirac Live software about acoustical variations in the vicinity of the PLP.

There are two versions of this pattern shown in the Dirac Live software and documentation, one for a chair with a single listener and one for a sofa with several listeners. The engineers wisely chose not to try to accommodate broader seating arrangements, almost a sure recipe for disappointing results.

A minor point: the sofa mic pattern shown in the documentation is not left-right symmetrical. I recommend always using a pattern that is left-right symmetrical for best soundstage and image clarity. My tests all used the chair mic pattern.

Other users have mentioned preferring the sofa setup pattern to the chair setup pattern, that it gave a more pleasing soundstage result. My own experience with different DRC implementations has been that more widely spaced mic patterns yield a more diffuse soundstage and softer imaging, not my preference at all. I will, when I am able, run Dirac Live setup with a wider mic pattern and report on the result.

Are nine positions enough? The answer depends a little on your philosophical priorities and what you hope for the averaging process to accomplish. Are you trying to optimize your sweet spot with DRC or make it bigger to include more listeners? DRC implementations tend to perform sweet spot optimization quite well, the averaging process assures correction is for an "acoustically typical" ear location in the sweet spot. The sound at the sweet spot is improved and the listener still has some freedom to move his head around. Using the averaging process to include more listening positions, usually the reason for needing more than eight or nine mic positions, only means that none of the listening positions sounds as good as it could.


Following are the frequency response measurements...
  • Without Dirac Live
  • With Dirac Live (1-Point), 2 target curves for the ESL
  • With Dirac Live (9-Point)
It appears from analyzing these plots that part of the Dirac Live design strategy was, above 250 Hz, to correct with less severity, allowing the contours that represent a speaker's characteristic sound tp remain while eliminating wider variations that detract from the listening experience. Below 250 Hz, the frequency response is flattened as much as possible.

This was seen with all three speaker examples, and strikes me as a perfectly-compromised approach. The mids and highs contain a speakers "voicing" signature. Below that you just want even response, no boomy notss and none that are shy or disappear.

It is also apparent that the more severe dips in response above 250 Hz have been left uncorrected, wise because these anomalies are pretty much untamable, varying widely within a small area, and are generally not heard anyway. The attackable dips below 250 Hz are sometimes eliminated completely.

All these details together speak of a well-thought-out and implemented design intended to correct that which can be corrected with minimum downside, and to do so in a way that is as musical as possible and respects the fact that many listeners like the sound of their speakers, and simply want to tame their environment a little. From what is visible in the measurements, and what I heard in listening tests, I say hats off to the Dirac Research engineers for a product excellently done.

The following screenshots are for the ESL speakers: using the default target curve with "my way" 1-point analysis, custom target curve with 1-point analysis, and custom target curve with "by the book" 9-point analysis.

The impulse response diagrams indicate a clear progression toward near-ideal, the by-the-book 9-point analysis, and very close matching between left and right stereo channels. The impulse response shown was determined by mathematical conversion. The impulse diagram is interesting in that it contains all frequency and phase information in one nice little waveform. It is a bit hard to interpret, but fairly easy to compare at a glance and see that one is "more ideal" than another.

Test Tracks and the Hair-Splitter Grading Scale
  • Atoms For Peace - Default
  • B-52's - Ain't It A Shame
  • B-52's - Revolution Earth (mono, for quick image clarity check)
  • B-52's - Vision of a Kiss
  • Beethoven - F. Reiner - Chicago Symphony Orchestra - Symphony No. 7 In A Op. 92 - 2. Allegreto
  • Cincinnati Pops Orchestra - Star Trek (the movie) - Main Theme
  • Joni Mitchell - California
  • Melody Gardot - Baby I'm A Fool
  • Mindy Smith - My Holiday
  • Nickel Creek - Ode to a Butterfly
  • Radiohead - Weird Fishes--Arpeggi
  • Radiohead - Packt Like Sardines In A Crushd Tin Box
  • Radiohead - Pyramid Song
The following scale is meant for hair-splitting. Grades 4 through 6 are all very close to the same, representing listening qualities that most users would be happy with, differences small enough that direct A-B comparison would usually be needed to hear them.

  • 6 = Superb
  • 5 = Excellent
  • 4 = Very Good
  • 3 = Good
  • 2 = Fair
  • 1 = Poor
Listening Tests: Frequency Response

All three of the speaker sets used for evaluating the DDRC-22D hardware were set up with little or no toe-in, so the wide listening angle called for some high-frequency correction (except for the Level Three Towers with their wide dispersion).

As the measurement plots show, Dirac Live was able to resolve and match the frequency response to the desired target curve with very little error. I like that the resulting frequency response was not exactly flat to target. One can see the sonic signature of the speakers showing through just enough to retain its individual character while getting rid of distracting variations. And with the NSM bookshelf, the rough area of integration with the subwoofer is nicely flattened out.

The default target curve suggested by Dirac Live has an almost straight downward tilt from +3 dB @ 30 Hz to -3 dB at 16 kHz. I prefer just a little more brightness than that, so my target curve was flattened from 600 Hz to 6 kHz, then rolled off to -3 dB at 16 kHz. With all three of the test speaker sets, the result was very listenable. The sweet spot allowed for plenty of head movement and regular listener position adjustments for comfort. Significant variations due to placement and acoustics appeared to have been compensated for, and the individuality of the speakers remained intact. Dirac Live seemed to be living up to its promises. Bear in mind that frequency response correction alone is the easiest of the tasks to be accomplished by DRC (in some cases the only one undertaken). The remaining categories to be discussed are much more difficult. But we will not minimize what has been accomplished so far, and accomplished very well.

The centered synthesizer on Ain't It A Shame stands out as it should, left behind in the mix by many speakers. Guitar tones, like those on Weird Fishes and Ain't It A Shame are accurately represented. Orchestral instruments, brass instruments, and vocals all were as they should be. I could find no instance of instrumental or vocal tonality which seemed less than accurate. Overall the sound of the Dirac Live correction had no sound to speak of, which is what you want to hear.

Listening Tests: Soundstage and Image Clarity

A great soundstage results from complex factors. Having dedicated countless hours to soundstage optimization and equalization, it is clear to me that EQ or DRC can be used to improve an already-good soundstage, but they cannot create something from nothing. Where a superb soundstage already exists, DRC implementations tend to degrade it slightly. It seems a reality that the finest soundstage performance is reserved for those who tweak their systems by hand endlessly, and that is as it should be. There should be some reward for fanatical attention to detail.

DRC is for a bang-for-buck type of audio system addition, a way to get great results with minimum bother. Dirac Live accomplishes that extremely well.

Two of the speaker sets were set up for the best possible image clarity and soundstage. The Level Three Towers were purposely set with zero toe-in, slightly off from their known best orientation, an additional challenge for the Dirac Live correction to overcome.

A subtle effect was noted with some of my Dirac Live results, one which I have heard with other DRC products, too, that I will refer to as a sort of mosaic effect. The best soundstage is seamless and cohesive. At times the Dirac Live soundstage seemed pieced together, like a mosaic of soundstage pieces that do not quite match up where they join. On Weird Fishes, the snare drum sound through the intro has a small field of reverb extending to its right. Without Dirac Live, that reverb sounds like a natural extension of the snare drum. With Dirac Live, in two of my three test cases, it seemed not to belong with the snare drum, almost like it was out of phase. Overall, the soundstage slightly loses its ability to totally convinced a listener of its natural reality.

This is not a major complaint, but it might matter to some listeners. The effect is subtle, and might not be noticed without direct A-B comparison. In my case it could be compared to the hand-EQ soundstage reference with only a couple seconds of switching time. As previously mentioned, the effect is a common artifact with DRC in general. I expect that many listeners would consider it a miniscule sacrifice compared to the more obvious benefits from using Dirac Live.

MartinLogan ESL

The ESL started out with the best soundstage and image clarity. Both were superb with no EQ or correction. The ESL had optional hand-tuned EQ to compare to, two bands and one shelf applied to mid and high frequencies, also delivering superb quality level.

Dirac Live "my way" (1-point) sounded much like my hand-tuned setup, only not quite as open and refined. Dirac Live "by the book" (9-point) gave an excellent soundstage, very close to the quality of the hand-tuned, even wider. I liked the extra width, but that mosaic effect was a detractor.

Image clarity suffered slightly with Dirac Live. The drumstick clicks on Weird Fishes went from pinpoint sharp with rock solid placement to softball-sized with position slightly uncertain in the soundstage. These were not major concerns, many would not consider them problems at all. Hair-splitting aside, the Dirac Live soundstage and image clarity on the ESL pair were fantastic, really fun to experience.

The width and distribution of the soundstage struck me on Default. In some ways it almost seemed better organized than the original.

Melody Gardot's voice on Baby I'm A Fool was a little larger with Dirac Live and had a slight tendency to wander. It is a very difficult voice for most speakers to localize. I enjoyed the way the orchestra was separated a little farther from her voice. Mindy's voice on My Holiday was also a little soft with a tendency to wander, and the strummed guitar at the beginning of Vision of a Kiss lost its punchy impact.

I think the lesson here is don't mess with perfection. Those who already have a first-rate soundstage, not easy to come across, are not likely customers for gear like this anyway.

But different listeners have different preferences, and there were some real treats to be heard with the same setup. The second movement of the Beethoven symphony never sounded better. With this recording I have gone back and forth on how well I like the micing and mixing. Using Dirac Live, it almost sounded as though the entire orchestra had been re-seated for sound. The Star Trek track also sounded marvelous with Dirac Live. Perhaps for mixes which are more dense in nature, like a symphony orchestra, Dirac Live provides separation of images in a way that speakers alone are not able to. I found myself wishing I could keep the eval unit just for listening to orchestra tracks with.

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HTD Level Three Tower

Starting out with the purposely less-than-optimally-set-up Level Three Towers, I expected to hear the greatest improvement with Dirac Live active, and that was the case. As the table of results indicates, the soundstage without correction was not bad, although nothing to be impressed by. Soundstage quality with Dirac Live my way (1-point), was much better, wider, more open, much more distinct. With by the book (9-point), it was better still, better organized and better balanced.

The degree of seamlessness was OK at all test settings. The ability to fool the listener into believing the music was live was not quite there.

Imaging was a little soft without Dirac Live, and went a little softer still with both of the Dirac Live setups. The four drumstick clicks at the beginning of Weird Fishes are an instant giveaway. Other imaging reference points are Cindy's locals on Ain't It A Shame and Mindy'a vocals on My Holiday. All were significantly softer and broader with Dyrac Live, and harder to localize. This is not a huge surprise. The ability of DRC to improve image clarity is limited at best, and here the imaging ends up still quite respectable along with a very nice soundstage. Considering the setup starting point for those speakers, the end result was more than acceptable, and would certainly have been in the excellent range with a better initial setup.

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NSM Model 5

The little two-way Model 5 bookhelf speakers are imaging lasers. Image clarity on the Weird Fishes drumstick clicks was superb, pinpoint sharp in all test cases, including Dirac Live. Their soundstage was quite good without and better with Dirac Live, widening and opening up. The final soundstage was not the biggest I heard with Dirac Live in that room, but was impressively nice.

And completely seamless. Dirac Live could do no wrong with the Model 5 bookshelves, and I wanted to just sit and soak in the sound.

It was delightful to have a test case where Dirac Live improved all listening categories with no downside. That made me wonder if the other speaker sets might also be capable of more with Dirac Live, given the time to experiment and tweak them further. I am sure the technology is capable of more than I had time to squeeze out of it, but then part of the idea is to get results quickly, so that is what I went for.

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Listening Tests: Dynamic Response

With the Level Three Towers, dynamics really stood out beautifully. On the intro of Vision of a Kiss, the centered, strummed guitar and bass should both be punchy and full of impact. With Dirac Live, that punchiness really stood out.

Along with the softened imaging from the ESL pair, Dirac Live softened the dynamic impact of those same instruments.

Listening Tests: Clarity and Detail

There also was no noticeable lack of detail or clarity with the use of Dirac Live. Orchestral spring plucks on the Beethoven symphony had an intimate, close-up quality. I always listen carefully to the string picking on all the acoustical instruments on Ode to a Butterfly. The closely-miced guitar, banjo, fiddle, stand-up bass, and especially the mandolin all contain so much detail that it is hard to take it all in. Application of Direc Live took nothing away from any of these instruments that I could hear.

Female vocals, especially Joni Mitchell's on California and Melody Gardot's on Baby I'm A Fool, hand an energy, clarity, and intimacy that was very enjoyable. Dirac Live left all this perfectly intact.

Listening Tests: Audyssey MultEQ XT Comparison

The Martin Logan ESL speaker setup was also corrected with Audyssey XT, using a 7-point left-right symmetrical version of the 9-point mic pattern. The frequency response correction was very similar, but other differences were easy to hear.

The soundstage with Direc Live correction was more spacious, more open. The images making up the soundstage were more distinct and separate with more space between them. The Aydyssey XT soundstage was a little more run together. It had a slight edge over Dirac Live in terms of natural cohesiveness.

A fairer comparison would have been between Dirac Live and Audyssey XT32, which was not available for this test. I have heard numerous speakers with XT32 correction applied after having been set up for optimum soundstage and image clarity, and based on that experience I would say that the performance gap between Dirac Live and Audyssey MultEQ XT32 is small. Only an A-B test will tell for sure. I am hoping to procure an AVR with Audyssey XT32 for a direct comparison, but did not want to delay the review for that purpose.


I can enthusiastically recommend the miniDSP DDRC-22D as a truly Pro-Level DRC offering. The sonic ultra hair-splitters are probably more interested in their own hand-tuning techniques over DRC, but even they enjoy a break once in awhile. For most listeners, miniDSP's DDRC family provides a lot of tweaking flexibility while delivering top-notch results quickly and easily.

Dirac Live with the NSM Model 5 test case could do no wrong. The other test cases might have come closer to perfection with a few more tries. Remember that a better starting point gives better final results. There is no substitute for attention to detail when working with DRC.

But the main point is the bang for the buck that Dirac Live delivers, delivering great sonic results with minimum trouble at a reasonable cost from a company that stands ready to keep you happy.


4,838 Posts
Discussion Starter #71
OPPO PM-1 Planar Magnetic Headphones and HA-1 Headphone Amplifier Review

OPPO Website
PM-1 MSRP: $1,199
HA-1 MSRP: $1,199
Available Direct From OPPO.

by Wayne Myers


OPPO is the company that makes the Blu ray players that will play anything, right? Well, they are branching out. They have recently introduced products that take them in one new direction that is not surprising at all and in another new direction that you might not have expected.

The more surprising product is the PM-1 Planar Magnetic Headphone, intended for the critical listener. The more expected new product is the HA-1 Headphone Amplifier/DAC. Of course they were going to come out with a high-performance DAC at some point. The HA-1 is an asynchronous DAC wrapped up with a discreet, fully-balanced, class-A headphone amplifier, along with every imaginable input type. The product says OPPO all the way - super-versatility, first-rate performance, impressive quality, and a surprising price - and combined with me PM-1 headphones creates a serious personal listening environment.


The OPPO PM-1 is an around-the-ear, open headphone designed for the serious music listener, a planar magnetic design in a simple yet elegant package. OPPO chose not to slap you in the face with their brand on this product. I almost needed a flashlight to find the lightly etched logo, model number, and serial numbers, opposite of the way most 'phones are branded these days. The headband and ear pads are covered in soft leather, and these headphones are supremely comfortable, with just enough adjustment range. The tightness amount was perfect for me just sitting and listening, but just loose enough for them to slip off backwards if I got up quickly.

They fold flat, not super compact but compact enough to easily fit in a backpack or large purse. I would want a little extra protection for the leather ear pads, they seem like they could be easily torn by a sharp object competing for space while being transported. Other than that, the design looks reasonably durable, not as tough as some studio headphones made to take a severe beating, but tough enough for the kind of use most people put their "special" set of headphones through.

The cable is cloth covered, up to the last foot of its length, where it splits to two plastic cables and a separate mini plug for each ear piece. The mini plugs were clearly marked and pluged firmly into the headphone earpiece with a healthy click to tell you it was seated properly and would not pull out with a little accidental tug. The standard cable appears to be wired with separate ground conductors down to the 3-conductor 1/4-inch plug. An optional fully differential cable is available terminated to a 4-conductor connector.

PM-1 comes with a beautifully finished wood storage case. Optional differential cables are available.

The HA-1 headphone amplifier is a fully differential amplifier design employing hand-picked and paired discrete power devices in the power amplifier stage. Once the signal leaves the DAC, it stays in the analog realm right through the motor-driven precision volume control. The Class-A design runs hot, so no stacking, one must respect its need for good ventilation. The user who has never been around a Class A amplifier might be alarmed by this. My evaluation unit was very hot after several hours of idling, and that is how it goes with class-A amplification where devices have a relatively high bias current running through them constantly to keep them in their most linear range of operation.

OPPO designers were thorough about providing all possible popular input and output possibilities for the HA-1. There are single-ended differential analog inputs, and the same complement of preamp outputs. Digital inputs include USB, which will require driver installation on the computer side, TOSlink optical, SPDIF coaxial, and AESEBU-=balanced digital.

The front panel is simple and highly functional. A beautiful multifunctional 4.3 inch color display is accompanied by the precision volume control, the input selector switch (which also switches display functions), and the headphone connectors.



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The PM-1 have a laid-back high end and a very deep, very flat bass response, an overall very smooth-sounding profile, and are also extremely fast and clean. They are made for extended listening without listener fatigue. Where many headphones reach out and grab you with a unique sonic signature, the PM-1 have a neutral, do no harm presentation, almost daring you to find something to be annoyed with about them. My only disappointments with the PM-1 were that I found myself adjusting the 'phones position on my ears to get the most treble possible, and the soundstage was not very wide on some tracks.

The PM-1 had a way of revealing distortion, too. More than once I heard lower levels of distortion on recordings I was very familiar with, and went on a chase only to find it was in the original recording but my other reference headphones simply never brought it out like the PM-1 were able to. The somewhat brighter models I am used to probably tend to mask that distortion.

While I enjoyed most of my time with the PM-1, I was waiting for that moment when a threshold gets crossed and they go on my "gotta have them some day" list, but that never quite happened. I expect that with a slightly brighter high end it probably would have, because they are a very neutral and accurate-feeling headphone and do what they need to to not get in between you and your music.

The HA-1 USB DAC drivers download and installed easily with no parameters to select. The unit is plug and play. Plug in power, USB cable, and headphones, and start listening.

I downloaded the free HA-1 app from the Google Play store for my Android tablet that acts as a remote for foobar2000 via the FoobarConPro app, and the two apps and HA-1 remote worked flawlessly together for their overlapped volume, forward, reverse, pause, and play functions. I liked holding the tiny HA-1 remote in my hand while listening. Its tactile buttons were easy to operate with eyes closed.

I did not get a chance to operate the PM-1/HA-1 in full differential mode, supposedly an important part of the ultimate headphone listening experience. I have done so in the past with a computing product set up for A/B testing between the standard and differential setups. The difference was notable and certainly enjoyable, giving a wider presentation and a more open soundstage. For me it was not a "gotta have it" difference.

Headphones wired with separate ground conductors all way down to the three-conductor plug will probably give 80% of the benefits desired in a fully-differential configuration.

The PM-1/HA-1 duo is capable of delivering SPLs of 105 dB average with 15-dB-dynamic-range recordings, yielding peak SPLs of 120 dB. That seems like plenty to me.

The HA-1 analog performance specs approach the realm of being ridiculous, but that is part of what high-end audio us all about. If there is a chance in a billion that one freaky set of golden ears might ever be able to hear some level of distortion, the spec must be 100x better than that. Just remember that it is all good, clean fun and that we enjoy arguing about it almost as much as we do listening to it.

PM-1 Headphone Measurements

PM-1 bass response is very flat and goes clear down to 20Hz, Upper-mids and highs are somewhat laid back.

PM-1 distortion is very low. My measuremants at 80 dB SPL showed <0.5% at 30 Hz, <0.2% at 50 Hz, and <0.1% at and above 100 Hz (except for a few little 0.2% to 0.3% peaks between 100 Hz and 330 Hz, which showed up consistently.)

Impulse response shows only minor ringing at the transducer resonance point, and a fast die-out of that ringing.

Step response diagrams show fast response, minimum overshoot, overall very fast recovery times for the PM-1 transducers.

Individual Test Scores

Measurement Methods

Go to the Headphone Roundup Overview for scoring and comparison details.

  • Test Scores
    • Very-High-Frequency: 9
    • High-Frequency: 9
    • General: 8
  • Weighted average (x1, x1, x2): 8.5
  • Weighting in Overall Performance Score: x2
  • Test Scores
    • Bluegrass track: 6
    • Funk Band track: 8
  • Average: 7.0
  • Weighting in Overall Performance Score: x2
  • Test Scores
    • Cymbal, loud track: 10
    • Bass, loud track: 10
    • Cymbal, quiet track: 10
    • Cymbal, loud track: 10
    • Strings, loud track: 10
  • Average: 10.0
  • Weighting in Overall Performance Score: x2
  • Test Scores
    • Deep bass track: 10
    • Lows track: 10
    • Mids track: 10
    • Upper-mids track: 10
    • Highs track: 10
  • Average: 10.0
  • Weighting in Overall Performance Score: x2
Frequency Response
  • Frequency Response Profile: Tilted
  • Test Scores
    • Deep bass track: 10
    • Lows track: 10
    • Mids track: 10
    • Upper-mids track: 10
    • Highs track: 10
  • Average: 10.0
  • Weighting in Overall Performance Score: x4
Overall Listening Experience
  • Score: 8
  • Weighting in Overall Performance Score: x4

Listening Tests

Imaging: 8.5 - Imaging with the PM-1 was quite good, although not stellar. It was always very stable, no smearing or wandering, but was a bit soft at mid frequencies.

Soundstage: 7.0 - The soundstage varied from quite good on some tracks to quite narrow on others. It was relaxed and natural, but the sensation of the soundstage moving out of the head and in front of me took awhile and was not fully engaging and convincing.

Clarity: 10.0 - Here the PM-1 stole the show. They were so clear that I was hearing distortion in familiar recordings for the first time. It was the nature of the PM-1 to be very revealing of inner detail like that.

Speed: 10.0 - The PM-1 handled these test tracks perfectly. Planar Magnetic technology is known for its responsiveness. The impulse and step response tests also show low amounts of ringing and fast recovery times.

Frequency Response: 10.0 - Frequency response is very smooth, tilted downward above 1 kHz. Although more laid-back than I prefer, it was so smooth and unobtrusive that I chose to give it a perfect score here and subtract a point from the "overall listening experience" score to note my personal preference.

Track Hopping

The Shins - Port of Marrow, all tracks - This superbly-recorded album literally begged to be heard from beginning to end on the PM-1, and was a delight to hear with their simple, honest clarity of presentation. I liked the way they brought out a slight liquid edge in the way James Mercer's lead vocals were recorded. Every track had subtle sonic detail held in reserve for a revelatory delivery device like the PM-1 to unlock. They pull apart the density of such a recording, allow the listener to hear the almost-invisible sounds in between the sounds. Had the PM-1 been graced with a couple dB more upper mids and highs above 1 kHz, I have no doubt they would have enslaved me and the "gotta have them" threshold would have been crossed easily while hearing this album. The beautiful chorus on 40 Mark Strasse got several plays at high levels - the PM-1 and HA-1 can deliver peak SPLs around 120 dB with average SPLs approaching 110 dB on a low-dynamic-range track, and never make the volume level obvious by distorting.

Tesseract's progressive metal Altered State album got sampled with the PM-1/HA-1. Bass response with the PM-1 is flat and deep. Those who insist on emphasized bass might find this a disappointment, and with flat 'phones that drop off below 50 Hz, the bottom end can seem weak. The PM-1 bottom end JUST begins to droop at 20 hz, and tracks with low bass content like many on this record are likely to teach one a new appreciation for flat, DEEP bass. This music also invites one to nudge the volume higher and higher, and it stays so clean it is wise to glance at the color display once in awhile and monitor levels for safety.

Nickel Creek - Ode to a Butterfly - This old favorite revealed the narrowness of the soundstage. Mandolin and guitar, usually just inside the left and right speakers, almost came from points side by side via the PM-1, all four acoustic instruments crowded onto a tiny stage shoulder-to-shoulder.

B-52's - Ain't It A Shame - Also a prime test track. The wide synth parts came from fairly wide points left and right, but the nearer-in instruments were all crowded together close to the center of the mix. The PM1-redistributed soundstage was not a favorite point for me. The distorted vocal at 3:24 - "your color TV" - was the first example of recording distortion that the PM-1 revealed.

Tower of Power - Fanfare, You Know It - Here the soundstge felt wider. The PM-1/HA-1 treat horns and brass right, and the big band sounded great on them.

Cincinnati Pops Orchestra - Introduction to 'Also Sprach Zarathustra' (From 2001 & 2010) - altered version; Cincinnati Pops Orchestra - Star Trek (the movie) - Main Theme - The big, beautifully recorded orchestra sounded great on the PM-1/HA-1. Here the soundstage was wide and well distributed. The bells and cymbals on the second of the tracks stood out with a nice balance. The detail and clarity of the violins was very nice, never got buried or strident on the hotter passages on this track.

Joni Mitchell - California - Joni's voice sounded as perfectly represented as I have heard it on a any speaker or headphone. The PM-1/HA-1 are all about truth without hype.

Radiohead - Weird Fishes--Arpeggi The four drumstick lead-in clicks can tell one a lot about imaging. Fairly tight with the PM-1, they should well be tighter, should be mere pinpricks of images.

Devin Townsend - Disruptr - I definitely missed the hotter high end on this track's cymbals.

Overall Listening Experience: 8 - For all those good qualities, I had to subtract a point for the highs being a little more laid back than I like combined with the narrow soundstage, and another because the PM-1 never pulled me over the "gotta have them" threshold. That said, I enjoyed listening with them very much. Their "do no harm" clarity and smoothness should appeal to listeners with a preference for an accurate and transparent, although somewhat laid-back, presentation.

Non-Listening Scores
Comfort: 10 - Supreme, luxurious comfort is what you get with the PM-1. Contact pressure is perfect, but be careful if you move around quickly, or they might slip off.

Design: 9 - The design is simple and sturdy. The PM-1 are attractive headphones that do not stand out or show off. One has to look close to find the OPPO brand - an understated confidence on OPPO's psrt. I held back a point because I wanted something about the design to grab me, not be quite so laid back (as with the high-frequency profile).​

Overall Performance Score: 9.0 out of 10

Other Factors - not part of the Overall Performance Score
  • $100 reference headphone: No
  • Drivable with portable media devices: Yes. PM-1 are quite sensitive and can be driven by virtually any media player or amp.
  • Usable without equalization: Yes
  • Isolation (if closed design): n.a.

The OPPO designers outdid themselves with the HA-1 design. There is absolutely nothing I could imagine wanting that they did not include, and did so absolutely beautifully. It is a marriage of no-compromise audio performance perfection with everything-you-can-think-of-functionality and a "Yeah we thought of that, too" user interface. The HA-1 should be high on any audiophile's list of Headphone Amp/DACs for audition.

The PM-1 planar-magnetic headphones had many really strong points, excelling with their clean, neutral presentation and speedy response. I only hold back slightly for its laid-back high end and a bit more for its somewhat narrow soundstage on some tracks. But the PM-1 is worth considering where a neutral, clean "window" into the music is required.

The HA-1 Headphone Amp Pros:
  • Stellar audio performance specs.
  • Analog signal path stays analog after leaving the DAC, precision motor-driven volume control.
  • Every input type you can think of.
  • Well-thought-out user interface.
  • Color status/metering display.
  • .
The HA-1 Headphone Amp Cons:
  • None
The PM-1 Planar Magnetic Headphone Pros:
  • Smooth frequency response.
  • Deep, flat bass.
  • Extremely low distortion.
  • Fast response drivers with little overshoot or ringing.
  • Luxurious comfort second to none.
The PM-1 Planar Magnetic Headphone Cons:
  • High frequency response a little too laid back for my taste.
  • Soundstage compressed on some tracks.
PM-1 Planar Magnetic Headphone Performance Summary and Overall Performance Score
  • Imaging: 8.5
  • Soundstage: 7.0
  • Clarity: 10.0
  • Speed: 10.0
  • Frequency Response: 10.0 (Tilted Profile)
  • Overall Listening Experience: 8
  • Comfort: 10
  • Design: 9
  • MSRP: $1,199
  • Overall Performance Score: 9.0 out of 10
Go to the Headphone Roundup Overview for scoring and comparison details.

Go to the OPPO PM-1 Planar Magnetic Headphones and HA-1 Headphone Amplifier Review Discussion Thread.


4,838 Posts
Discussion Starter #73
miniDSP nanoAVR HD Review

miniDSP Website
nanoAVR HD MSRP: $249
Available Direct From miniDSP.

by Wayne Myers


The miniDSP nanoAVR HD is a recent introduction from the company that has brought us an entire family of audio DSP products in recent years. I was intrigued by the concept of the nanoAVR as soon as I heard about it, and was anxious to have a chance to review a unit.

When it first came out, it was called the nanoAVR 8x8. Now miniDSP is calling it the nanoAVR HD. And the prices just dropped from the initial $299 to $249.


As the name suggests, the unit is very small, a mere 1.22 x 6.34 x 7.87 inches in a sturdy metal chassis. The product puts its focus on the heart of AVR communication, the HDMI interface. There are two HDMI inputs and a single HDMI output. That is the grand total of signal I/O for the nanoAVR. There is a USB connector and an Ethernet connector, for connection with a configuration control computer, Windows-based. Once configuration is complete, the nanoAVR can run stand-alone if desired, with one of four saved configurations selected from the front panel. The front panel is ultra-simple, a single push button and eight indicator LEDs, a group of four showing the selected configuration and a second group of four showing selected input and unit status.

The nanoAVR processes only the audio portion of the HDMI input bus selected. There is no video processing, and there is no Dolby or DTS processing, so audio input and output is in PCM format, up to 24 bits at up to 216 k-bits-per-second. Internal processing runs at 96 kHz, with 32-bit internal processing.

Two software plugins are available for the nanoAVR. Both support a full complement of input and output processing options with any-to-any selectability of the 8 input and output lines per HDMI bus. One of the plugins includes LFE / bass management capability.

The nanoAVR comes with a USB cable, an Ethernet cable, an HDMI cable, and a power supply.

nanoAVR HD Product Datasheet
nanoAVR HD User Manual
nanoAVR HD Plug-in Datasheet



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That nanoAVR user interface is very well thought out and extremely intuitive. The experimenter who hates to have to open up the user manual will probably get by just fine by poking around and will quickly see how everything fits together. On the other hand, the documentation is also very well-written and easy to follow.

There is always more than one way to navigate from Point A to Point B. On numerous occasions when contemplating a leap from one part of the interface to another, I found myself thinking how handy it would be to get there "this way," would click on a control, imagining it to be a super short-cut, and on every occasion someone had thought it all out ahead of time and that shortcut worked. Think in terms of the minimum possible number of mouse-clicks to get from Point A to Point B, give it a try, and it is already implemented for you. This is the level of attention to detail in design and implementation that makes a product like the nanoAVR a real joy to work with.

The simplicity of the product forces you to think ahead how you are going to listen to the changes you are making as you program the nanoAVR. There is no way to get audio directly out of the unit, it must be followed by an HDMI-empowered processor of some sort to get the individual audio signals where you want them to go.

I listened carefully while making all kinds of changes, including from configuration to configuration, and in no case did I ever hear any kind of pop or click or glitch. Most transitions were instantaneous or very near so, but even changing from one configuration to another where there was a short silent pause, there was no sign of glitching.

The little nanoAVR is quite simply a powerhouse of first-rate audio processing capability, fronted by a pro-grade graphical user interface.

Configuration Implementation Test 1

After familiarizing myself with the NanoAVR, I decided to go through the process of implementing a couple of unique configurations to see how long it would take and if any unexpected results might turn up along the way.

The first was a 2-channel 3-way crossover with a single sub channel with two independently-EQable outputs. As previously mentioned, the only way to hear the changes being made is to run through an HDMI-capable AVR of some sort. Not wanting to subject unprotected speaker drivers to unruly signal changes, you would want to disconnect them from your AVR outputs while doing this, for safety.

Here is where a small pair of full-range speakers come in handy to attach to the outputs being worked on. I also made use of an HDMI-to-Audio adapter, a $30 unit, any number of which are readily available from internet sources. If using one of these, remember that it only gives you the left and right main outputs, and the output is only active when a stereo signal is running. A handy nanoAVR user interface feature might be the addition of a solo bus where the output bus under test or being worked on could be soloed to the left or right main output for easy speaker or headphone monitoring.

The interface is broken up into three blocks, first the LFE and bass management, then the switching matrix, and then the outputs. It took me less than a minute to select the front-left and front-right inputs to go to the LFE management bus and turn off the rest of the inputs. Selection is a single mouse-click to toggle on or off. Or a right-click opens up a volume slider with the option of direct numeric input. Each of the inputs also has an optional low-pass filter. I left these at their 80 Hz defaults.

At each available filtering point of the interface, there is a complete list of filter types and slopes available. Crossover sections have an advanced mode that allows for bi-quad filters as well.

The main routing matrix, where I spent about another minute of programming time, allows for any-to-any routing between inputs and outputs, again with the option of simple on-off toggling or treating each point as a variable-level mix point. The matrix is 8 x 8 with a ninth internal channel handling the LFE mix, which has its own 8 x 1 x 8 routing matrix, effectively making the design a 9 x 8 configuration.

I selected front-left and front-right to be the main low-frequency outputs, sub out and center out as sub outputs from the LFE channel, SL and SR as mid band outputs, and RL and RR outs as tweeter band outputs. The matrix points for the tweeter bands were set at -3db to compensate for a sensitivity difference.

There were two very nit-picky interface features that I wished for. One was a eturn-to-zero feature that would allow a double click on a volume slider or control to reset it to unity (0 dB) gain. The other wish was that if a gain level for a given matrix point had been changed to a non-zero gain value, that it would be represented by a different shade of gray than "0 dB" or "Off," so it would be easy to find when switched "Off." But these were wish list items on an otherwise flawless user interface that went above and beyond expectations at almost every turn.

The most time was spent on the 3rd portion of the interface, the output programming, where the crossovers were set up. The user will be thinking about each output as a frequency band and the high- and low-pass filter points for that band. Available filter types are Butterworth, Linkwitz-Riley, and Bessel, with selectable slopes.

With the crossover configuration window open, one can see both the graphical representation of the band being modified, and the numeric input and descriptions of the low and high pass cut-offs. It is easy to switch between channels and any channel can be linked to any other in pairs to cut the programming time in half. Each of the subwoofer outputs had a couple of dips added to the parametric EQ section to control room resonances. These also could be linked together if desired. Setting up the crossover pairs, frequency bands, and sub EQ took less than 20 minutes, including experimenting time.

With that done, the nanoAVR configuration was in place. All changes take place in real time within the nanoAVR unit when made from the GUI on the controlling computer.

Each track has both a bar graph and a numeric representation of the RMS signal value at its output. This helps you eee at a glance where you have signals routed, and is needed when any EQ with boosted frequencies is in use, and when setting up optional channel compression. I would have liked to have seen a peak-reading meter, but they can eat up a bit of processing power.

Master output gain and input selection are also selectable, plus a number of functions can be programmed into popular remotes, including output gain.

Configuration Implementation Test 2

The second configuration project was to create, with a base 7.1 surround set-up, a custom headphone mix for a hard-of-hearing listener, sacrificing the RL out and RR out channels to that headphone mix output.

The LFE management remained unchanged from its default settings. The routing matrix took a little more thought, I chose to reroute the rear left and rear right outs to be mixed with the surround left and surround right outs with zero attenuation. That way a 5.1 source would play correctly, and the few less-common 7.1 titles would play almost correctly. Each of the new headphone mix outputs received its signal from Front channels, a -3db Center signal, and the surround and rear signals at full strength. LFE signal was not included, as that would only be a distraction to a hearing- disabled listener trying to follow dialog.

The only output channel changes were the enabling of compression. There is one compressor per output channel, with basic but adequate threshold, ratio, attack time, and release time controls. Some final output gain was added to compensate for compression, and the configuration was complete.

Configuration Implementation Test 3

My final experiment was to see how easy it would be to import filter values from Room EQ Wizard (REW) using a previously measured room response. REW allows for selection of several miniDSP platforms, including the nanoAVR. REW's designer, John Mulcahy, has worked with the miniDSP team to implement filter selection and file format to be compatible. Only 10 bands per channel of parametric equalization are available. Being one who prefers to avoid EQ overkill, I believe this to be plenty for most applications.

Going through REW's processs of determining correction filter values, once the needed filters have been defined, they are then manually saved to a file. Then that file is simply manually imported into the nanoAVR parametric EQ configuration screen and the nanoAVR settings now reflect the values that were determined by REW.

Audio Quality

The nanoAVR delivered first-rate audio performance through all of my tests and experiments. Its 24/96 I/O depth and speed, combined with 32-bit internal processing, will satisfy demanding listeners.


I took on the nanoAVR review with high expectations, and those expectations were satisfied at every turn. The tiny unit is packed with audio processing capability, has an outstanding user interface, and is sure to delight experimenters and tweakers with special audio needs for their surround system. The nanoAVR HD is a dynamite offering from the miniDSP team, and gets my full recommendation, along with my challenge to just TRY to work with one without having a fun time!


4,838 Posts
Discussion Starter #74
Axiom Audio LFR880 Floorstanding Speakers and ADA-1250 Power Amplifier


LFR880 with DSP Unit: $3750
Real Wood Walnut Finish: $490
ADA-1250 Amplifier: $2540
Available From Axiom Audio
by Wayne Myers


My first exposure to Axiom speakers was at the Home Theater Shack $3500 Speaker Evaluation Event in February of 2014, where we evaluated their M100 speakers. We reported that the soundstage and image clarity created by the M100 were impressive, and Axiom then asked us to evaluate a pair of their LFR880 speakers. Soundstage creation is what the LFR880 were designed for, so I looked forward to the chance to try them in my "typical living room" setting. The challenge would be for them to create first-rate soundstage and image clarity, to accomplish it with minimum setup fuss, AND to be able to do so when placed close to the front wall of the room, where soundstage and imaging are mediocre to nonexistent for most speakers.


Axiom's engineering and manufacturing facilities are based in the Muskoka district of Ontario, Canada. Their web site refers to the area as "unspoiled", which I can attest to, having backpacked in the area in recent years. At night, you can count the number of lit-up light bulbs per square kilometer on one hand. "Undiscovered" might be a better descriptor. There amid the lakes and trees and rocky hills and wildlife, the Axiom team has been designing and building speakers for over 30 years.

Why mention this? My impression of the Axiom products I have worked with is that they reflect many of the characteristics of their birthplace: they are beautiful, tough, massive, authoritative, natural, and no-nonsense functional.

I recently received the LFR880 speakers, along with their accompanying DSP-1 unit, and a four-channel ADA-1250 power amp for review. The LFR880 was introduced last winter, and reflects their version 4 (v4) set of design advances, which include:
  • A redesigned titanium dome tweeter.
  • Advances in crossover design to reflect advances in speaker performance measurement techniques.
  • Woofer and midrange drivers are constructed with die-cast baskets.
  • A high-powered version of the 6.5-inch woofer can optionally be requested, giving one the "high-powered" model of the speaker, wherein the woofers can handle higher power levels and broader excursions. The model reviewed used standard woofers.
And the design of the LFR880 itself is special. One of three omnidirectional models, with midrange and tweeter drivers on the back of the cabinet as well as on the front, each cabinet radiates a roughly omnidirectional sound power pattern - more to the front and rear than to the sides - for the purpose of helping to create an expansive, engaging soundstage with precise image clarity under conditions where a typical loudspeaker would not normally be able to.

Using rear-mounted drivers is not a new idea, but the Axiom team has taken steps to enhance it. The rear set of drivers is powered by a separate amplifier and receives its signal from a DSP unit which tailors both the front and rear signals to give flat power response (averaged) around the LFR880 speaker cabinet. Apparently a lot of testing went into determining the ideal on-axis and averaged omnidirectional responses. Add a 5-position selector switch for tailoring the level of the rear signal to room acoustics and closeness of the cabinet to the front wall of the listening room, and we have a set of design features that put the LFR880 into a category of its own.

This means that four channels of power amplification are required, two per cabinet. The power amp and DSP can be located in the same chassis, but I requested a higher-powered model, which came in its own chassis and also gave me the ability to evaluate the power amplifier on its own.

LFR880 Speaker

Each LFR880 cabinet contains two woofers, two midranges, and two tweeters on the front surface, wired to an internal passive crossover, terminated to bi-wiring-capable 5-way binding posts on the rear. There are four terminals, normally strapped together in pairs, with a bi-wiring split between woofer and midrange/tweeter sections of the crossover. This is essentially the same configuration as the Axiom M80 model.

On the rear there are two midranges and two tweeters at the same enclosure heights as those on the front, with their own passive crossover terminated to a pair of 5-way binding posts.

The design yields an enclosure that is deeper and heavier than one might expect. The cabinet sides are non-parallel to reduce standing waves, 9-1/8 inches wide at the front and 7-1/8 inches wide at the back of the cabinet. A bass-reflex design, there are two reflex ports on the rear and one on the front of each cabinet, Axiom's vortex design which randomizes airflow through the port to eliminate resonances and port noise. I requested optional port plugs (four total) for the rear ports to experiment with the bass level at different distances from the wall, and was glad to have them.

Front and rear grilles are magnetically attached, held in place firmly yet are easy to remove, and snapping right back into position when replaced. I enjoy the contrasting look of the white woofer and midrange aluminum cones, clean and straightforward but definitely techie. With grilles in place the LFR880 looks dressy and formal.

I had seen Axiom's standard Black Oak finish with black grilles in February, a simple but sharp satin finish with a coarse grain - just right for the home theater where you want to avoid light reflections from glossy surfaces. The LFR880 finish for this review was a custom Real Wood Walnut finish in Satin Low Gloss, a $490 adder per pair. The medium-grain Walnut says "understated elegance", not drawing attention to itself, but gorgeous upon inspection. They would fit in beautifully in any formally-decorated room. An array of available finishes includes the stock Black Oak and Boston Cherry, six grille colors, twelve custom vinyl choices, "match your walls" by color code or sample, and different gloss levels, including piano gloss. Construction and assembly quality were flawless. There was not a single instance where anything physical about the speakers drew attention to itself as a potential problem. Tamper-resistant hardware holds drivers and terminal plates in place.

The LFR880 speakers are made to create a soundstage, which targets them as two-channel, or stereo, listening speakers. They could work in a multi-channel music or home theater setup, especially if phantom center channel is implemented, but I focused my evaluation on the intended stereo application.

DSP-1 Digital Signal Processor

The stand-alone DSP-1 has its own heavy-duty steel chassis with heavy aluminum face plate, painted dark brown. The front panel contains only a blue power-on LED and the machined-in Axiom logo.

The rear panel contains six RCA connectors: Left Input, Left Front Out, and Left Rear Out, Right Input, Right Front Out, and Right Rear Out,

The rear-mounted selector switch had positions marked Near 2, Near 1, Normal, Far 1, and Far 2. The LFR880 rear output level increases in that order, with higher output level intended for positions farther from the listening room front wall. The only function provided by the DSP-1 is frequency response shaping for front and rear outputs, and the 5-position level control for the rear driver. The design has been changing, as my order was held up until early August by pcb artwork changes.

Also on the rear panel is a power switch. AC input voltage must be selected when the unit is ordered, there is NO manual or automatic selection of input voltage.

ADA-1250 4-Channel Power Amplifier

The unit is simple, tough, and heavy. Both the ADA-1250 and the DSP-1 bristle with the heads of tamper-resistant screws. The power amp has both front and rear power switches and a front-mounted blue power-on LED.

The rear panel has an RCA input and a dual-banana output connector per channel.

Inside is a 4-channel switching power amp fed by a linear power supply. Efficiencies are claimed to approach 90%. The LFR-1250 provides the power needed for the LFR880 in a medium-sized room to stay clean even when one nudges the volume into the LOUD zone. There were times that this was hard to resist.



LFR880 Speaker
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DSP-1 Digital Signal Processor
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ADA-1250 4-Channel Power Amplifier
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Associated Review Equipment

  • Asus G74SX Laptop, Intel I7-2670QM @ 2.2 GHz, 16 GB DDR3 Memory, Room EQ Wizard, foobar2000
  • Digital Audio Workstation, Phenom II x6 1100t @ 3.5 GHz, 16 GB DDR2 Memory, Room EQ Wizard, foobar2000
  • Media Server, Phenom II x6 1055t @ 2.8 GHz, 8 GB DDR2 Memory, Room EQ Wizard, foobar2000
  • Roland Quad-Capture Audio Interface
  • M-Audio Firewire 410 Audio Interface
  • Beyerdynamic MM1 Measurement Microphone
  • XTZ Room Analyzer Pro Measurement Microphone, Courtesy XTZ, Home Theater Shack Sponsor
  • Onkyo TX-SR705 Receiver
  • Crown Xs500 Power Amp
  • OSD Audio ATM-7 Digital 7-Zone Dual Source Speaker Selector with Remote Control
  • MartinLogan ESL Hybrid Electrostatic Loudspeakers
  • Home Theater Direct Level 3 Tower

At the setup position shown in the first diagram: LFR880 frequency response at tweeter height at the Listener Position (LP), mid-room setup for best soundstage and image clarity without DSP or rear drivers, then DSP and rear drivers added for the measurements shown, Near 2 setting. Room effects are strong at low and mid frequencies and are different between the left and right sides, The 12deg off-axis listening angle gives very slight HF rolloff. Impulse response shows strong first reflections from rear delivers, all other reflections dissipated & randomized. The impulse response shows a strong first reflection from the rear drivers with other reflections randomized, hallmarks of strong soundstage production.

In-room response at 1.5 m on the tweeter axis.

Response 2 feet out from the front wall, at 1.5 m on the tweeter axis.

Response of front drivers only, no DSP used, 2 feet out from the front wall, at 1 m on the tweeter axis. This is essentially the same as Axiom's A80 design.

Distortion at 85 dB SPL stays below 0.5% above 130 Hz.

Step response, 2 feet from wall, 0, 1, and 2 rear port plugs. The ringing at 56 Hz is undoubtedly due to room effects.

Affect of port plugs on LF response at 2 feet from the wall.

Polar response plots, actual measured response and 10 mS gated response at 1.5 m mid-room. Mic position did not move. Angle adjustments were made by turning the enclosure to adjust its angle relative to its front-center pivot point, so room effects changed very little from plot to plot. Plots were run every 5° from 0° to 60°, then at 75° and 90°.

Impedance measurements for the front driver section show how the impedance at the LF resonance point rises as one port plug, and then a second port plug, is added to control LF boominess closer to the wall. The second plot shows the impedance measurement for the rear drivers.

The Quest For Soundstage

In the time period from August 2013 to February 2014, Home Theater Shack held three Speaker Evaluation Events during which HTS evaluators reviewed six to eight speaker pairs over each weekend at the home of then-HTS-owner Sonnie Parker. It quickly became apparent to those involved that the first priority of setting up each pair of speakers was achieving a wide, deep, spacious soundstage with precise image clarity and, where possible, with well-defined depth acuity. Without exception, we found it necessary to locate the speakers well into the listening room, away from the front wall of the room, to achieve these goals. The time delays of the reflections from the front of the room create that soundstage, and there seemed to be no substitute for space from the front wall.

In response to HTS member requests, most of those speakers were briefly tested while located close to that front wall. It was apparent that none of the models we evaluated could sound their best that way, and we advised readers to save their money and buy inexpensive speakers if they would have to be located against the wall of their listening area.

The LFR880, a new Axiom model when we were setting up our last event, did not fit the cost criteria and could not be included. They are made to be soundstage creators, even when located close to the front wall, and I was anxious to hear how well they could fill that claim.

Evaluation Approach

The LFR880 speakers were first evaluated in their ideal (or so I thought) setup location, away from the wall, well into the room. With no DSP running and using only the front drivers, I found their best setup, as shown in the diagram in the Measurements section. Adding rear drivers and DSP enhanced that soundstage wonderfully, while imaging stayed solid and precise.

The ideal setup involved an off-axis listening angle. I also tested with the speakers aimed directly at the LP from the same spot on the floor. While frequency response was certainly better that way, and the soundstage was wider, the imaging was softer. Preferring the tighter and more precise imaging, I went back to the off-axis angle, and listening tests were completed that way.

Close to the wall, performance was best with enclosures angled inward, the LP straight on-axis. The LFR880 speakers were evaluated with the back corner (angled as they were) of the cabinets 4-6 inches, 12 inches, 18 inches, and 24 inches out from the front wall.

Mid-Room Listening Test

While settling in, I was reminded how important listening height can be with different speakers. Most comfortable seating will put an average listener's ears at about 35 to 37 inches high. I was perched forward on a sofa and was troubled by the high end from the LFR880. Then I realized my ears were about 3 inches higher than ideal. After a seating adjustment got them down to 35 inches, the highs felt smoother and more natural and relaxed. This would probably not be a problem with the speakers farther away, but in this configuration with dual tweeters it made a noticeable difference.

Starting with Todd Rundgren's Pulse, the imaging of the sampled synthesized and natural xylophone notes, each mixed to its own individual location in space, was tight and precise. The bells, cymbals, and triangles on Compassion, Shine, and Healing I, II, III from the same album, Healer, were all clear, crisp, natural, and precisely placed in the soundstage. Triangles are difficult for many speakers to localize, but the LFR880 had no trouble keeping them where they were mixed. Percussion throughout the frequency range was tightly defined and natural. The synthesized strings on Shine had a nice balance and natural tonality. Bass was somewhat accentuated but still enjoyable.

The soundstage and imaging without DSP and rear drivers had been very good - natural, wide, and deep, clearly defined with tight imaging. It was a surprise to find that everything about the soundstage improved with the addition of the rear drivers and DSP. It was bigger, deeper, more spacious, more clearly defined, and depth acuity, the most difficult characteristic to achieve, went from very soft to noticeable. (Great depth acuity comes with a clean, symmetrical listening room and can be enhanced acoustically - I had neither for the LFR880, wanting to hear how well they could fare in a typical room.) Imaging stayed every bit as solid and tight. This was an impressive start.

The highs were very even and clear. Metal dome tweeters are sometimes uneven and harsh. I never felt that with the Axiom tweeters, redesigned for the version 4 line of products. They might not win in a direct comparison to a good ribbon tweeter's liquid smoothness, but being part of an authoritative voicing profile, they were made to crank out powerful highs cleanly and did so with finesse and transparency.

Before proceeding, I used Compassion to compare the raw front driver soundstage with the front-rear-DSP soundstage at different DSP settings.
  • Front Drivers Only, No DSP: Cymbals were sharp, very present. Bass was centered and solid. Bells sounded like they were in the room, well defined. Sibilants were sharp (mixed that way) but clear.
  • Near2 DSP - for use closest to the wall: Imaging remained excellent while the soundstage became larger and better defined.
  • Near1 DSP: The soundstage was slightly larger, no change in image clarity.
  • Normal DSP: The soundstage was even larger, no change in image clarity.
  • Far1 DSP: The soundstage was even larger, image clarity started to soften slightly.
  • Far2 DSP - for use farthest from the wall: The soundstage was even larger, image clarity definitely softer, still very stable.
Nickel Creek - Ode to a Butterfly::
Near2 - The soundstage was narrower than I was used to hearing it on this song; the mandolin pulled in toward the fiddle rather than just inside the left speaker enclosure. Soundstage and imaging (SS&I) were very clear and natural.
Normal - SS&I were livelier, like the room had grown, and seemed even more natural than before.
Far2 - Now all instruments were moved toward the center of the soundstage, and there was a loss of definition and image clarity. The setting might be too much for this configuration and might be better in a treated room.

Nickel Creek - Reasons Why::
Far2 - As with the previous track, instruments were all "centered," with some loss of image clarity. Really not bad over all, but not the best setting.
Normal - Back to a very nice soundstage, image clarity was back to tight and precise. The vocal harmonies were sharply placed. Tonality was great for this track and the last one, strong and authoritative.

B-52's - Ain't It A Shame:
Normal - The harmonica in the intro stayed exactly centered, every note. Few speakers can do this. Overall soundstage width was slightly less than normal, just noticeable.
Near2 - SS&I slightly improved. Tonality was nicely balanced, but the very top end of the gloss on Cindy's voice was missing, a casualty of the off-axis listening angle. A quick check with the Far1 and Far2 settings verified that high frequency response improved slightly, but I strongly preferred the better SS&I characteristics with the Normal through Near2 settings.

Tower of Power - Fanfare, You Know It:
Near2 - This setting was just right for this track.The soundstage was wide and deep, imaging was tight, tonality was right on for all instruments, and everything was placed right where it should be.

Gorillaz - Rhinestone Eyes:
Normal - I started with the Near2 setting, but preferred the Normal setting on this track, pushing the walls back with wonderful spaciousness and depth. I could tell that the right wall of the room was closer to the LP than the left wall in the way it limited the soundstage, but the effect was minor.

Cassandra Wilson - Strange Fruit:
Normal - This track is already big, but was made to sound even bigger by the LFR880 soundstage, while imaging remained tight. The trumpet, alone in the mix where a shifted position is easily detected if not properly managed in the soundstage, was right where it should have been. The Dobro guitar, almost left out by some speaker voicings, had a nice forward prresence.

The standup bass was quite boomy and felt flabby and loose. Adding a single port plug to a rear port on each cabinet tamed it nicely, attenuating the bass peak and tightening the flabbiness. After this, I played with the port plugs on a number of tracks, settling on one plug as being right for my listening room. The tightening effect made low bass tones seem more focused.

Civil Wars- Poison & Wine:
Normal - This track also seemed much larger than I had heard it before, yet the intimate voices remained forward, right up front.

Yello - La Habanero:
Normal - Here the soundstage was simply HUGE. It was beautiful, clear, and FUN! Percussion, bongos, and cow bell stood out as especially lifelike in the soundstage, all precisely imaged. This is an example of the kind of track you will start watching out for when you have a great SS&I arrangement. Perhaps not your favoritee kind of music, the mix crystalizes and solidifies in a great soundstage and is so much fun to hear that you might end up listening to it more than your old favorites that were drably mixed in SS&I terms.

Beethoven - F. Reiner - Chicago Symphony Orchestra - Symphony No. 7 In A Op. 92 - 2.;
Cincinnati Pops Orchestra - Introduction to 'Also Sprach Zarathustra' (From 2001 & 2010) - altered version;
Cincinnati Pops Orchestra - Star Trek (the movie) - Main Theme:
Normal - Once the Beethoven 2nd movement entered its first big crescendo, it was clear that I was enjoying the best orchestral soundstage I had witnessed in my home. The Cincinatti Pops sequence was wonderfully present yet grandly spacious, all instruments properly represented and distinctly separate. With one port plug, the deep booms at the beginning of Star Trek were clean and tight as well as deep and powerful.

Michael Hedges - Eleven Small Roaches:
With the Far2 setting, the solo acoustic guitar moved away and was less imtimate. The Normal setting was just right.

Atoms For Peace - Default:
Starting with the Normal setting, I then tried and preferred the Near2 setting for its tightness in handling the instant-on instant-off percussion sounds. The single port plug (at least) was an absolute necessity on this track.

Broken Bells - The High Road:
Near2 - This track also sounded best with the tighter SS&I, and again demanded the single port plug.

New Pornographers - Fantasy Fools:
A dense track, the Near2 setting again treated it the best, allowing the clearest SS&I presentation.

Close To The Wall Listening Test

Moving the LFR880 speakers close to the front wall, I expected to find them performing better than other speakers I had worked with, but not dramatically so. Was I ever in for a big surprise!

With the rear of the speakers 2 feet out from the wall and toed-in to point straight at the LP, the LFR880 was in its element. High-frequency response was flattened out and, while the soundstage depth was missing, the width of the soundstage was immense, very nicely developed, with excellent, tight, solid imaging. And the speakers completely disappeared into that soundstage.

As much as I had enjoyed the LFR880 in the mid-room setting, their performance at 2 feet out from the wall was even more fun. One would normally be trying to find ways to not say bad things about a speaker that close to the wall, but with the LFR880 it was exactly the opposite. They thrived in this location.

With the speakers angled toward the LP and the enclosures as deep as they are with their ream-mounted drivers, the front corner of the LFR880 enclosure was 3.5 feet into the room. That is a lot, but there are ways they can be dealt with decoratively, whereas pulling them into the center of the room is simply a no-go where there is a non-audio-fanatic involved in the decision process. I found that the speaker-LP-speaker triangle could be set with the speaker spacing smaller than the triangle height without soundstage width suffering. The inward angling of the speakers, leaving the rear drivers angled outward, pushed the soundstage far wider than the speaker spacing would allow one to expect.

Closer than 2 feet, using the Near2 DSP setting, the SS&I started to lose some clarity and definition. Close-to-the-wall SS&I performance is summarized as follows:
  • 24 in.: Excellent. Soundstage (SS) was wide and spacious, 6 feet beyond either enclosure, clearly defined, and imaging was tight and solid - a pinpoint sound in the mix was the size of a marble or smaller and clearly localized.
  • 18 in.: Very good. SS width slightly reduced, 5 feet beyond either enclosure, imaging still tight and solid - a pinpoint sound in the mix was the size of a marble or smaller and clearly localized.
  • 12 in.: Good. SS width markedly reduced, 3 feet beyond either enclosure, imaging started to soften - a pinpoint sound in the mix was the size of a softball or smaller and localization was somewhat indistinct.
  • 6 in. or less: Fair. SS width very limited, 1 to 2 feet beyond either enclosure, imaging was very soft - a pinpoint sound in the mix was the size of a basketball or smaller and localization was very indistinct.
In all of these cases, the enclosures were pointed directly at the LP, so frequency response was excellent.

At the 24 in. out from the wall position:
  • Near2 - SS&I was narrowest, but was very full, clear, and tightly defined.
  • Near1 - SS&I widened slightly, but also became less clear.
  • Normal - SS&I was very wide, but image clarity softened noticeably.
  • Far1 - SS&I wider, but image clarity very soft and unclear.
  • Far2 - SS&I slightly wider, but image clarity suffering.
While many of these descriptions do not sound very complimentary as they approach the wall, bear in mind that in most cases the performance was far better than any other speaker I had worked with that close to the room boundary, with one possible exception (a model in our Feb. 2014 HTS evaluation event).

While I had planned this part of the evaluation to be fairly brief, I was so taken by the SS&I performance at 2 feet out that I spent quite awhile listening with the LFR880 located there. They simply defied all logic. And when pushed up to HIGH volume, the room simply came alive. They could do no wrong in that configuration.

Overall, I thoroughly enjoyed the LFR880 speakers. Their authoritative voicing profile - a fairly flat profile with a slight downward slant from bass to treble - can grow on you, but might not appeal to those who like the snap of a small presence peak around 2 kHz or so. And the delicacy and refinement of the mids and highs in some competitive models might be preferred by others. But these are subtleties to be sure, and those who thrive on soundstage and imaging are likely to fall for the clean, even, authoritative presentation of the LFR880 loudspeakers from Axiom.

ADA-1250 4-Channel Power Amplifier

I had requested that the DSP unit and the power amplifier come as separate units - an available option - so I could evaluate the power amp on its own. The ADA-1250 is a Class-D - or digital - amplifier, switching at a frequency of 350 kHz, and has a linear power supply (the web site mentions "our Class D power supply," but I was informed that it is linear). Noise and distortion specs are excellent.

Why go digital? Power efficiency can be very high, up to 90% with the ADA-1250. Efficiency increases with higher power output. That kind of efficiency can help one feel a little greener, but in day-to-day use it also means the unit stays cool when working hard, with no cooling fan required. Cooling fans stay internal and higher packaging density follows.

How did it sound? I ran the LFR880 speakers at high volumes with tracks containing volume levels 10 to 12 dB below full scale where full scale was set to reach 115 dB SPL peak. For short periods of time, that is. The results were always wonderfully clean. Like the LFR880 speakers, the ADA-1250 power amp thrived upon those opportunities to deliver volume - there was never a sense of strain or holding back, only of open, bottomless reserves of power. When asked to play softly, it could do so just as well.

I also ran the ADA-1250 side-by-side with an Onkyo receiver and a Crown power amp, able to instantly switch among them. I noticed that the ADA-1250 was emphasizing sibilant sounds. Upon investigation, there turned out to be a 3 dB frequency response peak 10 kHz when driving my MartinLogan ESL electrostatic speakers. Electrostatics are known to present reactive loads which can be challenging to power amps. As shown in the curves below, taken at the amplifier output terminals, the Crown amp stayed flat at high frequencies (so did the Onkyo), but the ADA-1250 did not. Step response with the reactive load of the ESL showed somewhat-extended ringing, possibly affecting its ability to keep up with high-speed dynamics. When driving a conventional 3-way speaker, the ADA-1250 stayed flat and fast, as did the other amplifiers. Distortion measurements under all conditions showed very low levels of noise and distortion.

HF peaks resulted when the ADA-1250 drove an electrostatic speaker. Step response showed extended ringing with the ADA-1250 driving the electrostatic speakers.

Other than driving the electrostatics, the ADA-1250 sounded natural, open, capable of delivering immense amounts of reserve power, and is a worthy amplifier to consider, especially with Axiom speakers, which LOVE to play loud. Potential buyers should be aware that the ADA-1250 must be ordered with either a 110V or a 220V power supply, it has no way of being switched from one to the other by the owner/user. A convenience that few would ever make use of, it is often absent in audio products with linear power supplies.

The final question is the price. The price for the LFR880 pair does not cause me any hesitation in recommending it. When it comes to amplifiers, there are many available in the $1000 to $2000 range that have similar capability and specifications. You can pay a lot more, too, when extreme specs, special capabilities, or brand mystique are involved. The ADA-1250 has its strengths and charms, but they might not be enough to justify the price for many buyers.


There was a time I would have said that a stereo listener about to purchase speakers to be used close to a wall in his/her room should prepare to put up with the inevitable lack-luster performance, save the money, and purchase inexpensive speakers that look nice. With Axiom's new LFR660 and LFR880 omnidirectional loudspeakers and their accompanying DSP units, it is a whole new ball game. Next to the wall they sound good, a foot out they sound very good, and two feet out they sound fantastic, producing soundstage and imaging I would never have imagined were possible in that placement. Numerous finishes are available, including real woods like the beautiful Walnut that I received.

The accompanying ADA-1250 four-channel power amp, while not at its best driving an electrostatic speaker, is a great match with the LFR880, if a bit pricey, but with solid capabilities, admirable performance specs, and deep reserves of power to deliver clean volume and dynamics.

If you are adding or upgrading stereo speakers in a room where esthetics are paramount and insist that the speakers stay close to the wall, and are hoping to find speakers that deliver serious stereo performance and look beautiful doing it, save yourself some time and put the LFR880 Floorstanding Loudspeakers at the top of your audition list. You will not be disappointed.


4,838 Posts
Discussion Starter #75
Linkwitz Labs

  • LXmini (kit, with DSP, plus pipe and fittings, without amplification): $690
  • LX521 Constant Directivity Reference Monitor (kit, with DSP, without amplification): $3,058
Siegfried Linkwitz has been spreading the good word about audio via his Linkwitz Lab web site since 1999. Part of that good word seems to be Good sound does not have to cost an arm and a leg. His innovative speaker designs are sold in kit form after you buy the plans directly from Linkwitz Labs.

His rooms at the last two audio shows I attended for HTS were always crowded, and I had never made it to hear what all the fuss was about. This year I committed to make that room a priority. Some of my thoughts in the past have been along the lines of How good could they really be? Now I know the answer.

To put it simply, very, VERY good! And even a little better than that!

When I entered the room, there was only one chair empty in the back, and as at shows gone by, I started to leave. But Siegfried's lovely wife Eike directed me to sit, and obediently I did. Luckily the front-center chair opened up a moment later.

I had been listening to the LXmini speakers, and was already impressed. They seemed not to need a carefully-centered sweet spot to cast a grand soundstage. The tiny LXmini consists of two drivers, a LF driver mounted at the top of a damped PVC pipe, providing an omnidirectional pattern up to 700 Hz, and a Mid/HF driver facing the listener in front of a smaller section of damped PVC pipe, providing a rear-diffused dipole pattern above 700 Hz. A miniDSP unit provides an active Linkwitz-Riley crossover (yes, Siegfried put the Linkwitz in Linkwitz-Riley) and equalization for the two drivers. Four channels of amplification are required, two per LXmini tower.

Note that the positioning of the two drivers helps create crossover directionality in the acoustical realm. The Linkwitz Lab web site, and undoubtedly the purchased plans as well, give a wealth of theoretical information about the design in a readable style targeting the DIY hobbyist.

How did the LXmini sound? The room easily garnered on of my Wow! awards for the show, and I had not even heard the bigger LX521 monitors yet. I started listing descriptors without embellishment, as though the LXmini had as much right of ownership over those descriptors as their designer had over the crossover type named after him:
  • Virtual Point Source
  • Full
  • Even
  • Flat
  • Clean
  • Precise
  • Unified
  • Dynamic
  • Honest
  • Natural
  • Humble
In normal listening positions, especially the front-center LP, the room was filled with sound that emanated from space in the most real and natural way possible, creating a huge, deep soundstage with pinpoint imaging wherein those humble, rustic little PVC-mounted speakers completely disappeared - Don't need to show off visually, 'cause in the audio realm I've got it nailed. Moving closer to one tower allowed one to hear its point-source unity, unsurpassed by any single-full-range or small-two-way design that I have heard, with the soundstage-producing advantage of omni-directionality at LF and dipole characteristics at HF. I am curious what a similar design with crossover at around 200 Hz would perform, putting all of the critical soundstage- and imaging-producing frequencies into the dipole driver's range, but it is difficult to imagine it sounding significantly better than the LXmini.

LXmini plans cost $105 from Linkwitz Labs. The LXmini materials are available in kit form from Madisound for $525, including the miniDSP unit and program, to which the builder adds PVC pipe and standard fittings, plus 4 channels of amplification. It is a Wow! of a DIY project if I ever heard one, attention-getting in its elegant design and arresting in its audio impact.

The LX521 Constant Directivity Reference Monitor, a four-way fully-dipole design, performed much as the LXmini had done. It added DEEP bass - the deep booms on Stravinsky's Firebird had kick-you-in-the-gut impact - and filled the room with a completely natural soundstage and flawless, pinpoint imaging. The LX521 could pump out much higher volumes and appeared entirely capable of being thought of as reference speakers.

Kit price for all CNC-cut wood pieces, ready to assemble and finish, along with the 12 SEAS drivers and an assembled and tested custom analog signal processor (using a miniDSP unit is also an option) adds up to $3058, a pricier setup to be sure, but one sure to please the most particular of audiophiles.

4,838 Posts
Discussion Starter #76
Three Headphone Review - Audio-Technica ATH-M50, Sennheiser HD 280 Pro, Sony MDR-V6

ATH-M50: $199 / $129 [Website]
HD 280 Pro: $99 / $99 [Website]
MDDR-V6: $109 / $79 [Website]

by Wayne Myers


This review is about three closed-back headphones that retail at around $100. Although the MSRP range covered by the three models included is 2:1, they are very similar in capability, performance, and street price.

These are not high-end headphones. They are the kind of 'phone one can use for fun-serious listening, yet be comfortable taking on a trip or packing to the office and back every day.

This review is not a shoot-out, but is a comparative review and will include discussion of the strengths and weaknesses of each model. It will conclude with Headphone Roundup scoring.


These three models share the following characteristics:
  • Closed-back design for listening privacy and some noise isolation.
  • A coiled cord, which is the standard for headphones in the price range. It is too bad. As convenient as the coiled cord might appear, to me they are just a nuisance.
  • 1/8-in TRS plug with 1/4-in TRS screw-on adapter. All three screw-on adapters use the same screw-on thread. The one photographed on the MDR-V6 is a replacement, in this case made by Shure.
  • Fold-up design for travel or storage. The MDR-V6 folds up the tightest and stays that way the best.
  • Studio-use design. The user can reverse-fold either earpiece and hold by hand against one ear, the other ear exposed to hear the room, like a vocalist might do while recording in studio.
  • Well-built and can take a beating.
  • Emphasized bass response, although only a little with the Audio-Technica's.
  • They have all been around for many years. It is not difficult to catch good deals on them, even well below the street prices listed above.
  • They all get asked about a lot.
  • I own all three and have a lot of experience with them.
  • All were purchased because there were indications of some sort (i.e. I saw a curve somewhere) that each might have a pretty flat frequency response. Alas, none of them do.
The Audio-Technica ATH-M50, the most expensive, tries its hardest to be the most refined of the three. The Sennheiser HD 280 Pro sounds the worst with music, but can fulfill a need that the others can not. And the Sony MDR-V6 butts into the territories of the other two and in many ways steals the show.

Listening Scores

Frequency response is generally the most obvious sonic differentiator for comparing headphones. The ATH-M50 (score=9.2/10) has the smoothest response below 1 kHz - but is shy on depth in the lowest registers - then has the commonly seen and oh-so-carefully-executed "scooped-out" region of the curve from 3 kHz to 7 kHz that keeps them from sounding harsh and eliminates listener fatigue - without messing up the tonality of brass and string instruments - then finishes with the 9 kHz peak that makes the treble range sound balanced and not dull. There is a slight bass-emphasis tilt to the voicing, making the ATH-M50 sound large at the bottom-end without being boomy. This all works together really well for the ATH-M50, they are very enjoyable headphones with any kind of music.

The MDR-V6 (score=8.8/10), however, has one of the flattest high ends above 1 kHz that exists in the headphone world. It will seem overly-bright to some, especially with that last 7-to-9 kHz peak, but it is smooth enough that I really like it. If they would only have kept the low frequencies under control - personal preference, of course. The lows come off stonger than I care for, although smoothly done, and extend quite deeply. Even with the extra bass, I find myself drawn to that high end. Truth be told, they are my favorite travel 'phone. The bass cuts through the rumble of the road or jet engines, the highs stand out beautifully, and physical factors (later) are particularly suited for travel.

The HD 280 Pro (score=6.0/10) is a studio tracking 'phone, plain and simple. Lower-mids are emphasized so performers can hear the pitch to follow, highs are reduced for long sessions without fatigue, the bass emphasis keeps everyone on the beat, and first-rate isolation prevents mic bleed-through. The few times I have put on the HD 280 Pro to listen to music, they sounded so strange that I could only do so for a few minutes. My reason for including them in this review group is that they do get asked about and noticed in music stores and in video clips of recording sessions, and one can be tempted to think they must sound pretty special for that kind of exposure. Buyer beware, they can work well in one application and poorly in another. I can not recommend them for serious or casual music listening.

Imaging and soundstage are scored separately. The Audio-Technica ATH-M50 (ss=9.0/10) and Sennheiser HD 280 Pro (ss=9.0/10) both deliver wide, spacious, natural soundstages that are easy to relax into. The soundstage with the Sony MDR-V6 (ss=8.0/10) is not as wide or engaging, but is still quite good. Imaging on the MDR-V6 (im=10.0/10) is the best I have heard, they are my reference 'phones for imaging. Every sound is pinprick sharp. The Sennheiser's (im=8.5/10) also image well, but here the Audio-Technica's (im=6.5/10) fall short, imaging is soft and spreads out even more on sibilants and high-frequency sounds like cymbals and triangles and small tinkly chimes.

Clarity is very good with the ATH-M50 (score=9.0/10) and the MDR-V6 (score=9.0/10), even on dense, complex tracks with deep bass and delicate high sounds coexisting. The HD 280 Pro (score=7.0/10) can not keep up here, and clarity is only fair-to-good.

The Speed test is done with special tracks of fast pulses and sequences. The ATH-M50 (score=9.0/10) won the day here, could keep up with anything and never got muddy or messy. The MDR-V6 (score=8.0/10) did almost as well, and the HD 280 Pro (score=7.0/10) fell behind, getting muddy and hashy at times.

For the Overall Listening Experience, Audio-Technica ATH-M50 and Sony MDR-V6 both get 9/10, having lots of good qualities and being enjoyable to use. The Sennheiser HD 280 Pro gets a 6/10, not a great general listening headphone, but, as previously stated, that is not its forte.

Non-Listening Scores

The MDR-V6 gets 9/10 for Comfort and the same for Design. They are lighter, have a snug fit that is easy to forget you are wearing, stay on better, fold up smaller, stay folded up when you give them a toss, just keep doing things that have you saying, "Cool!"

The ATH-M50 and HD 280 Pro both get 7/10 for design - they work, but nothing grabs you as special - and 8/10 for comfort, which is good but not impressive.

Other Factors - not part of the Overall Performance Score

Audio-Technica ATH-M50
  • $100 reference headphone: No
  • Drivable with portable media devices: Yes.
  • Isolation (if closed design): 10.8 dBA
Sennheiser HD 280 Pro
  • $100 reference headphone: No
  • Drivable with portable media devices: Yes.
  • Isolation (if closed design): 15.6 dBA
Sony MDR-V6
  • $100 reference headphone: No
  • Drivable with portable media devices: Yes.
  • Isolation (if closed design): 12.4 dBA
Measurements and Specifications

Measurement Graphs
Audio-Technica ATH-M50

  • Closed-back dynamic
  • Driver Diameter = 45 mm
  • Sensitivity = 99 dB
  • Impedance = 38 ohms
  • Weight = 284 g without cable and connector
Frequency Response:

Distortion at 75 dB SPL - well below 1%.

Distortion at 85 dB SPL - approaching 1% at some frequencies, still very good.

Distortion at 95 dB SPL - above 1% at some frequencies, but well under control.

IM Distortion (DIN)
L @ 75 dB SPL = 0.86%
R @ 75 dB SPL = 0.92%
L @ 85 dB SPL = 1.0%
R @ 85 dB SPL = 1.1%
L @ 95 dB SPL = 1.9%
R @ 95 dB SPL = 1.8%

Impulse and Step Response: Very clean and fast for dynamic headphones.

Group delay:

Impedance: Driver matching is fair, impedance is consistent, easy to drive from any source impedance.

Sennheiser HD 280 Pro

  • Closed-back dynamic
  • Sensitivity = 102 dB
  • Impedance = 64 ohms
  • Weight = 220 g without cable and connector
Frequency Response:

Distortion at 75 dB SPL - well below 1%.

Distortion at 85 dB SPL - approaching 1% at some frequencies, still very good.

Distortion at 95 dB SPL - above 1% at some frequencies, but well under control.

IM Distortion (DIN)
L @ 75 dB SPL = 0.90%
R @ 75 dB SPL = 0.79%
L @ 85 dB SPL = 1.1%
R @ 85 dB SPL = 0.90%
L @ 95 dB SPL = 2.1%
R @ 95 dB SPL = 1.5%

Impulse and Step Response: More ringing than ATH-M50, and long recovery time. Will negatively affect speedy responsiveness on complex tracks.

Group delay:

Impedance: Driver matching not impressive, indicates driver matching is not great.

Sony MDR-V6

  • Closed-back dynamic
  • Driver Diameter = 40 mm
  • Sensitivity = 106 dB
  • Impedance = 63 ohms
Frequency Response:

Distortion at 75 dB SPL - well below 1%.

Distortion at 85 dB SPL - approaching 1% at some frequencies, still very good.

Distortion at 95 dB SPL - above 1% at some frequencies, but well under control.

IM Distortion (DIN)
L @ 75 dB SPL = 0.31%
R @ 75 dB SPL = 0.35%
L @ 85 dB SPL = 0.44%
R @ 85 dB SPL = 0.59%
L @ 95 dB SPL = 1.2%
R @ 95 dB SPL = 1.7%

Impulse and Step Response: Big initial overshoot, then fairly short recovery time. Will give fairly fast responsiveness, but not at cleanly as ATH-M50.

Group delay:

Impedance: Good driver matching = tight imaging.


If you like lots of bass and value a flat high end like I do, you might become attached to the Sony MDR-V6 (OPS=8.8/10), which is my favorite travel/toss-around headphone. The Audio-Technica ATH-M50 (OPS=8.6/10) probably has a more universally desirable sound signature and, all things considered, it is not hard to see how it has remained popular in the price range. The Sennheiser HD 280 Pro (OPS=6.9/10) did not score as well for general listening, but studio tracking is really what it was made for.

Audio-Technica ATH-M50
  • Imaging: 6.5
  • Soundstage: 9.0
  • Clarity: 9.0
  • Speed: 9.0
  • Frequency Response: 9.2 (Scooped Profile)
  • Overall Listening Experience: 9
  • Comfort: 8
  • Design: 7
  • MSRP/Street: $199/$129
  • Overall Performance Score: 8.6 out of 10
Sennheiser HD 280 Pro
  • Imaging: 8.5
  • Soundstage: 9.0
  • Clarity: 7.0
  • Speed: 6.0
  • Frequency Response: 6.0 (Tilted Profile)
  • Overall Listening Experience: 6
  • Comfort: 8
  • Design: 7
  • MSRP/Street: $99/$99
  • Overall Performance Score: 6.9 out of 10
Sony MDR-V6
  • Imaging: 10.0
  • Soundstage: 8.0
  • Clarity: 9.0
  • Speed: 8.0
  • Frequency Response: 8.8 (Flat Profile)
  • Overall Listening Experience: 9
  • Comfort: 9
  • Design: 9
  • MSRP/Street: $109/$79
  • Overall Performance Score: 8.8 out of 10

Audio-Technica ATH-M50

Sennheiser HD 280 Pro

Sony MDR-V6


4,838 Posts
Discussion Starter #77
Three Bluetooth Device Review - Pendulumic Stance S1 Wireless Headphone, Audioengine B1 Premium Bluetooth Music Receiver, Miccus Mini-jack TX4 Wireless Bluetooth 4.0 Music Transmitter


Pendulumic Stance S1 Headphone: $199 [Website]
Audioengine B1 Receiver: $189 [Website]
Miccus Mini-jack TX4 Transmitter: $65 [Website]

by Wayne Myers


Wireless technology has been edging its way into the world of high fidelity audio more and more in recent years. Bluetooth, with its recent aptX extensions, appears destined to take its place as a truly hi-fi wireless option. And when one has tripped over and stepped on as many wires and cables as I have over the years, a technology that can reduce cabling without sacrificing audio quality will at least get a thorough tryout.

This review covers three Bluetooth products which could find their way into an audio or home theater enthusiast's setup. We will cover the Pendulumic Stance S1 Wireless Headphone, the Audioengine B1 Premium Bluetooth Music Receiver, and the Miccus Mini-jack TX4 Wireless Bluetooth 4.0 Music Transmitter. All three are Bluetooth 4.0 devices and include aptX capability, which promises to deliver CD-quality sound. One of the three, the TX4 transmitter, is also Low-Latency capable.

High Fidelity Comes To Bluetooth

There are many profiles defined for Bluetooth, having to do with hardware form factors, data, and application types. The most common profile one will run across when discussing audio is A2DP, the basic stereo profile. Any Bluetooth product involving stereo sound makes use of this profile. The quality level is similar to a high-bitrate MP3, or the AC3 encoding that is part of the original Dolby standard. Lossy compression algorithms are employed to determine what parts of the audio signal can be thrown away to reduce the data rate while keeping the sound quality pretty much the same. "Pretty much" is the key idea here. The compression algorithms are designed around psychoacoustical principles to be transparent, but given the right equipment, program material, and a little guidance, almost any listener with healthy hearing can pick out the degradation that results.

Many listeners do not care, and for them the A2DP profile provides more than adequate sound quality, depending on application. But many do care, and for them there are higher data rates and newer codecs which make near-lossless, lossless, and even high-resolution Bluetooth audio possible. The aptX codec and its variants are the first of these bringing Bluetooth products to market for the serious listener, often with smartphone communication conveniences built in.

AptX technology is licensed by CSR, the British company which owns the patents. The levels of capability we are concerned with are as follows:
  • The aptX logo alone, which means CD quality - 16-bit, 44.1-kHz (16-44).
  • The aptX Low Latency designation, which means that latency, or delay times, in the neighborhood of 32 milliseconds are possible. Without that designation, latency times can be 100 mS, 200 mS, or even more. For streaming audio with no absolute time reference, that is not a problem. For watching a movie or television, video and audio end up way out of sync.
  • The aptX Lossless designation, which means that true byte-accurate audio transmission is possible. High-resolution 24-96 transmissions can even be accommodated. There are variables to choose from in the design of a given product, however, which can make it difficult to know what to expect if not clearly stated in product specs. One is the possibility of a near-lossless mode when data rates are compromised. Another trade-off is the possibility of extremely-low-latency audio, as low as 1 millisecond, with the trade-off of audio quality being limited to 48 kHz, or "DVD quality."
There are a couple of important rules to remember when looking at products and determining how well they will work together. The A2DP capability is implied where stereo sound is involved. Beyond that, assume nothing. In order for a transmitter and receiver to work together at any higher capability level, both must have that level of capability designed in, and should state it explicitly. For instance, a transmitter with aptX Low Latency capability and a receiver with aptX capability will be able to work together to provide CD quality sound, but not with low-latency delay times.

For this review, audio quality was verified using both listening tests and two measurement methods beyond the typical. The measurements are not straightforward because the encoding distortion we are talking about is created dynamically during changes in the music, so regular frequency response and distortion measurements do not trigger the generation of those artifacts. Short of expensive specialized gear, the best way I found to catch them was to identify a short musical passage that would cause the distortion, set up a loop using a Digital Audio Workstation (DAW - Reaper in this case) so it could be precisely repeated, and capture a spectrum analysis of the loop at the different quality levels in question. Zooming in on the high-frequency spectrum measurements, I found with A2DP that the strong frequencies which make up the main sound of small chimes were significantly attenuated, while weaker "side tones" which add richness to the sound were amplified, yielding a harsh or splattery sound. In every instance where the listening test indicated this dynamic distortion, it could be seen by zooming in and comparing captured high-frequency spectrum analysis plots. Where the higher quality aptX transmission was measured for the same passages, the captured spectrum analysis plots showed no such distortion.

The other measurement method, more general in nature, involved making a recording of a track which had passed through the transmitter-receiver loop, carefully lining up the recording with the original, inverting one, and summing them together. If the two recordings are identical, the result will be complete cancellation, and silence. With A2DP, the two tracks were so different that the naked eye could see the difference between the waveforms on the computer monitor. Even the time scaling managed to drift slightly on the signal that had been through the A2DP loop. With the signal that had been through the aptX loop, there was no drift in the time scale, and the two signals looked identical, although they were not quite. The hoped-for cancellation was almost complete, an indication that the aptX processes had changed the music very little.

What the measurements and listening tests indicate is that the A2DP quality signal is indeed lossy and roughly analogous to MP3 quality. The aptX signal quality level, on the other hand, proved to be highly accurate and the listening equivalent to CD quality sound, as advertised.


Measurement Graphs

Long-term noise testing was performed by preparing a 1-hour sine wave track to be played on one of several Bluetooth transmitting devices and receiving each with the B1 receiver while monitoring for noise that would indicate data errors. This method was first verified as effective with the following test waveforms:

Verification of Test Method

All signals are stereo.

A pure sine wave with no errors produced no noise outside the spectrum target (blue).

A 10-second sine wave with a single error byte produced this easily detectable noise profile.

A 10-second sine wave with one byte removed (shortened by one byte) produced this noise profile.

A 10-second sine wave with one byte added (lengthened by one byte) produced this noise profile.

A 10-second sine wave with one byte repeated (replacing the adjacent intended byte) produced this noise profile.

Test Results

Asus tablet to B1 receiver @ 6 ft, 15 ft, 20 ft, 25 ft:

Asus tablet to B1 receiver @ 35 ft:

LG G3 smartphone to B1 receiver @ 6 ft, 15 ft, 20 ft, 25 ft:

LG G3 smartphone to B1 receiver @ 35 ft:

TX4 transmitter to B1 receiver @ 6 ft, 15 ft, 20 ft, 25 ft:

TX4 transmitter to B1 receiver @ 35 ft:

TX4 to B1 Frequency Response:

TX4 to B1 Distortion - Measurement Noise Floor:

TX4 to B1 Distortion at -20 dB FS stays well below 0.1%:

TX4 to B1 Distortion - -5 dB FS stays well below 0.1%:

IM Distortion (DIN) - TX4 to B1:
@ -20 dB FS = 0.21%
@ -5 dB FS = 0.22%

TX4 to B1 Impulse Response, 2 mS view:

TX4 to B1 Step Response, 200 mS view, shows a small amount of sub-sonic overshoot, recovered from in one cycle, of no practical concern:

TX4 to B1 Step Response, 2 mS view, shows a small amount of high-frequency ringing, recovered from quickly; transient response is very good in the Bluetooth realm:

Total latency delay time:
TX4 transmitter to B1 receiver = 210 mS
TX4 transmitter to S1 headphone = 115 mS

Maximum input level @ TX4 input before clipping, TX4 transmitter to B1 receiver:
0.438 Vrms

Maximum input level @ TX4 input before clipping, TX4 transmitter to S1 headphone:
0.418 Vrms

Associated Review Equipment

Measurement Methods

  • Asus Nexus 7 Tablet (2013) with Android 4.4.4
  • LG G3 Smartphone with Android 4.4.2
  • Asus G74SX Laptop, Intel I7-2670QM @ 2.2 GHz, 16 GB DDR3 Memory, Room EQ Wizard, foobar2000
  • Digital Audio Workstation, Phenom II x6 1100t @ 3.5 GHz, 16 GB DDR2 Memory, Room EQ Wizard, Reaper Digital Audio Workstation, foobar2000
  • Media Server, Phenom II x6 1055t @ 2.8 GHz, 8 GB DDR2 Memory, Room EQ Wizard, Reaper Digital Audio Workstation, foobar2000
  • Roland Quad-Capture Audio Interface
  • M-Audio Fast Track C600 Audio Interface
  • M-Audio Firewire 410 Audio Interface
  • 3Dio Freespace Binaural Microphone, modified, custom HRTF correction curve
  • Mackie 402-VLZ3 Preamp/Mixer
  • Beyerdynamic MM1 Measurement Microphone
  • American Recorder SPL-8810 Sound Level Meter
  • AKG K 601 Headphones
  • AKG K 701 Headphones
  • Beyerdynamic DT 880 Premium 250-Ohm Headphones
  • OPPO PM-1 Planar-Magnetic Headphones, Courtesy OPPO, Home Theater Shack Sponsor
  • Sennherser HD 600 Headphones
  • OPPO HA-1 DAC/Headphone Amplifier, Courtesy OPPO, Home Theater Shack Sponsor
  • Emotiva Pro Airmotiv 4 Powered Studio Monitors
  • Fluke 77 Digital Multimeter

Pendulumic Stance S1 Wireless Headphone

I was invited by Mike Johnson of Pendulumic to audition the Stance S1 Bluetooth headphones at Rocky Mountain Audio Fest (RMAF) in October. I honestly expected an OK-sounding set of 'phones with Bluetooth added on. I was immediately impressed by the sound quality and asked to do a detailed review. The more I have worked with the S1, the more impressed I have been by all aspects of the design.

The Stance S1 is a sealed, on-the-ear design that works in three high-fidelity listening modes: Bluetooth, direct-cabled, or amplified-cabled, selected by a 3-way slide switch on the back of the right earpiece. A fourth Phone Control mode is available when wired or working via Bluetooth with a smartphone. A rechargeable internal battery can be backed up by a pair of AAA batteries. An on-off-on selector switch on the front of the left earpiece determines which battery type is in use for either of the two powered modes, or turns power off (direct-cabled mode). A volume control on the back of the right earpiece (Bluetooth mode only) doubles as a push-button multi-function control. When cabled to a smartphone, the cable also includes a simple multi-function Bluetooth control for music and phone calls. A microphone built into the right earpiece supports telephone talk in Bluetooth and cabled modes.

The Stance S1 comes with a USB charging cable, a 3-conductor to 4-conductor braided audio cable with inline media and phone control, a 1/8" to 1/4" adapter, a dual plug adapter for laptop audio interface, a travel case, and a manual and quick start guide.

Using my LG G3 smartphone with Android 4.4.2 and Asus Nexus 7 (2013) with Android 4.4.4 as music sources - neither has aptX capability - it quickly was evident that the sound quality was lossy. The track that showed this the most clearly was Todd Rundgren's Compassion, which makes use of a set of high-pitched chimes, stroked numerous times through the song. The recording quality on these chimes and on the cymbals is excellent, and the chime and cymbal tones are normally crisp and clear. Through the S1 headphones from my phone or tablet, I could hear the cymbals turn to hash and the chime tones splatter on impact. Dense male vocal harmonies also became muddy.

Switching from Bluetooth to cabled mode, or from using the A2DP-encoded source to no coding/decoding at all, cleaned up all those compression artifacts. (The user who wishes to try this for himself should be aware that the transition to Bluetooth includes a connect delay and various clicks, thumps, and beeps - all part of listening "under the hood" to a Bluetooth startup. And a quirk of the S1 design cuts Bluetooth mode volume by about half while the cable is plugged into the earpiece, something one would not do in normal use.) The S1 being driven straight from a headphone amp played all the aforementioned test segments with pristine clarity.

Back to Bluetooth mode, but receiving from the TX4 transmitter, with the aptX codec built in, the audio quality stayed pure and pristine. There is very little audible difference between the Bluetooth mode with aptX and the straight cabled mode, until you go to very high volumes, where the Bluetooth encoder/decoder circuitry will hard clip when overloaded. The TX4 transmitter and S1 headphone combination, benefiting from the aptX codec, was able to deliver 105 dB peak SPLs before clipping, so this is not likely to be considered a practical limitation for most users.

The S1 in cabled mode and in Bluetooth mode with an aptX transmission source performerd very well, as the measurements below testify, with frequency response, distortion, and dynamic performance sounding very much the same in normal use. The TX4 transmitter added some gain, about 12 dB, so the signal path needed to be managed to realize that equivalence.

The cabled-amplified mode has quite a different sound, with bass and treble both boosted relative to the midrange, although not severely so, a distinctly tailored sound. While I preferred the flat response of the other two modes, I can see some users enjoying this tailored response with rock and pop tracks. It was a little much for the sound of natural instruments - strings and horns especially tended to lose enough of their midrange tones to be distracting. The flat response of the Bluetooth and straight cabled modes, however was indeed very flat-sounding, and aside from a small amount of bass boost peaking at 100 Hz rivals the flatness of more expensive industry standard headphones by the likes of Sennheiser and AKG. The upper-mid and high-frequency ranges came across very smooth, flat, even, and natural, not an easy accomplishment at all. Distortion was low at medium and lower listening levels, and dynamic characteristics were very fast and clean for a product in its price range.

Listening Scores

In terms of scoring the S1 performance - using Home Theater Shack's Headphone Roundup scoring method - scores apply to the Bluetooth/aptX and direct cabled mode - soundstage and imaging were both very good. The soundstage was wide and spacious, very natural and enjoyable (9.0 / 10). Imaging was a little soft in the midrange but very stable and quite sharp overall (8.0 / 10). Dynamic response (9.0 / 10) with my speed tracks was very good as well, and clarity (8.5 / 10) only suffered as volume levels rose, and even then not terribly. I found no fault with the frequency response (9.6 / 10) except the bass being slightly emphasized, and it could have gone deeper but would only benefit from it on rare tracks, and the overall listening experience score was easy to give a perfect score (10 / 10) - the Stance S1 was simply a great-sounding set of 'phones to work with.

Listening Test Notes

Broken Bells, Perfect World:
BLUETOOTH: The kick drum starts in with good, tight focus, punchy, good depth, and fairly FLAT. High end - does not sound like a headphone high end, does not sound peaky, is pretty clean. Vocals sound very natural. The soundstage is BIG, spacious, natural. Are they reference flat? They sound close.
AMPLIFIED: tailored tonality, mids are pulled back, upper mids & highs are smoothed, pushed forward.
CABLE: Mids & top end very natural, very smooth.

Nickel Creek, House of Tom Bombadil:
BLUETOOTH: Beginning of this track is custom mixed to mono - Imaging is pretty good, 7 of 10. Second time, levels controlled more carefully, imaging is tighter, 8/10. String plucks are lively, lovely. Can JUST hear a little midrange dip, very slight. The standup bass sounds a little recessed.
AMPLIFIED: Strings still sound OK, a little recessed with mids pulled back.
CABLE: The bass is a little clearer, string sounds are a little more natural with mids slightly more present.

Mindy Smith, I Know The Reason:
BLUETOOTH: Imaging is definitely a little soft on the vocals. The vocal sheen is pristine, clear. Vocal handling is very nice. Bass goes quite deep. The midrange dip is JUST enough to keep the ear from being overwhelmed, not enough to the point where you feel you are missing anything, feels like it is all there and well balanced. Nice detail on plucked strings.
AMPLIFIED: Tailored sound, deeper scoop, works well for rock, pop, vocal. Upper-mids & highs really smoothed out.
CABLE:Mids definitely more natural, highs OK but a little recessed, tonality works very well. Bass seems tighter, better defined.

Todd Rundgren, Compassion:
BLUETOOTH: Can hear the LF resonance point. Want head straight or leaned forward slightly for positioning to get best upper-mids & HF. Volume control good resolution, multi-turn, nice design. Bells splattery - MP3-320K quality - with A2DP. Much better with aptX, CD quality. Dense vocal harmonies - mushy & less clear with A2DP, very clean with aptX source. Cymbals have good clear image placement. When I lean my head back and the 'phones shift slightly, I lose the high end - tightness vs. comfort always a tradeoff.
AMPLIFIED: Hear more bass resonance. Cymbals well defined, very clear, as are the bells.
CABLE: Cymbal & bell frequencies a little more natural w/o the amp.

Civil Wars, Poison and Wine:
BLUETOOTH: Top end really seems smooth, no peaky sharpness common with headphones. Deep bass is just the right amount, plenty strong and DEEP. When song volume rises, can hear compression (A2DP) - Bluetooth, not the 'phones. Better with aptX, hear no compression. Sibilants sound crisp, not harsh.
AMPLIFIED: Upper bass a little strong, hear some distortion on voices.
CABLE: Upper bass clear again, mids just right for me.

Cincinnati Pops, Gayne Ballet, Adagio (from '2001')
BLUETOOTH: Strings warm and natural. Hear a creaking - no that is my neck. Volume UP - at max, get a couple of "volume warning" beeps, a little loud, could be softer. So far all instruments sound very natural.
AMPLIFIED: Not so natural.
CABLE: Strings definitely have a more natural sound.

Scott Davie (Rachmaninoff), Lilacs:
BLUETOOTH: Missing a little of the Overs piano tinkle in the upper-mid scoop. Hear a little processing distortion (A2DP). On the weakest part of the track, top tinkle fell into the scoop.
AMPLIFIED: No tinkle at all. Where did it go?
CABLE: Same as Bluetooth.

Midlake, Roscoe:
BLUETOOTH: At 1/2 hour of listening, beginning to notice slight discomfort from ear pressure. Good detail on guitar sounds. Really good soundstage.
AMPLIFIED: Good sound for rock with vocals.
CABLE: Better bass balance.

Tower of Power, Fanfare, You Know It:
BLUETOOTH: Top volume good, not excessive, pretty good safety point, maybe up around 90 with hotter mixes. Can just hear the scoop on the horns & sax, but still sound natural, any more and they would suffer, but just OK.
AMPLIFIED: Horns not good.
CABLE: Much better horn sound than amplified, sax way more natural.

Muse, Supermassive Black Hole:
BLUETOOTH: Nice stereo width. Nice rock high end, stays clean at high volume. Wide sounds are really wide in the soundstage.
AMPLIFIED: GREAT for rock tracks like this, a little accent at bottom & top, not so obvious here.

Atoms For Peace, Before Your Very Eyes:
BLUETOOTH: Kick drum rise time maybe softened a bit, not muddy, but not sharp, either. Hear one bass peak, certain tones are accented a little. On this track the Bluetooth process distortion (A2DP) barely is noticeable in certain spots, sufficiently clean for most listeners. Bluetooth/A2DP not at critical listening quality, though, need aptX for that. Like the spaciousness of big reverb sounds. Does the closed design hold in the reverb, keep it from getting away, make it sound even bigger? Distortion on lowest notes at end of track.

Todd Rundgren, Pulse, ending:
BLUETOOTH: xylophone notes very focused, good tone.
CABLE: YES, more natural, better focus, more punch.

Non-Listening Scores

Design: It is as though all aspects of the design "go to 11." From the initial un-boxing through multiple listening and measuring sessions and just wearing them around the house listening for fun, they continued to draw smiles of admiration. They are solid and durable, fold flat, and come with a tough, compact carrying case, complete with a zippered inner pocket for accessories. All controls are easy to find and operate. The volume/push-button knob is designed after the classic windup knob found on wrist-watches. It is easy to find and operate, simply a tactile marvel, "practically perfect in every way," with a nice little mechanical feedback "click" as it is turned in either direction. The S1 is very comfortable, with leather earpads and adjustable-tension headband (9 / 10, only because you do notice them, but only after quite awhile, and there are 'phones out there that you could wear for days), they stay on well (although shifting slightly with head movement), they look sharp, they feel good in your hands, they include rechargeable and backup battery modes, they can be used cordless or corded. Score for design: 10 / 10, even though there were a couple of flaws. To use them cabled with a regular 3-conductor-connector source, the user will need a 3-conductor to 3-conductor cable, not supplied, and not explained; and the supplied 1/8" or 1/4" adapter will not work properly with the supplied cable, also not explained. STILL, they get 10 points for design, everything else works that well. The design team must have stayed up late many nights bringing the S1 to fruition. Or maybe there were elves or fairies involved.

Operating range (not scored), line-of-sight indoors, was only about 25 feet, with any of my Bluetooth sources, but there are higher-powered devices that would certainly increase that range. At 25 feet, an occasional drop-out ensued, annoying enough one would venture no farther. Latency is not low, but that is a separate design target perhaps to be addressed in another model, so no points lost. Latency was 115 mS with the TX4, a number that will vary with the transmitter in use. That is long enough to be annoying where sync to video is involved. A fast rock drummer will easily appear a beat ahead of the sound on a YouTube video, for instance.

Measurements and Specifications

Pendulumic Stance S1

  • Type = Closed-back dynamic
  • Driver = 40-mm (1.6in) neodymium driver
  • Sound pressure level (SPL) = 110dB (1 kHz / 1 Vrms)
  • Impedance = 32 Ohms
  • Weight = 220 g (8oz) without cables or accessories
  • Bluetooth® version = 4.0 with aptX®
  • Frequency response = 15Hz – 22kHz (10Hz – 24kHz with aptX® enhancement)
  • External battery = 2 x AAA batteries
  • Wireless playback duration = up to 30 hours (with external AAA batteries)
  • Wireless operating range = up to 50 feet (15m)
  • Ear Cup Diameter = 70mm (2.7in)
  • Materials
    • Robust steel headband
    • Aluminum-steel alloy
    • High-quality bonded leather
    • Braided cable
Frequency Response of the three music listening modes; Bluetooth and Cabled modes are almost identical, very flat-sounding with slight bass boost; the Amplified response (bottom) has enhanced treble and bass:

Cabled Distortion at 75 dB SPL - well below 1% above 100 Hz, peaking near 1% at 70 Hz, all in all very good dynamic headphone performance:

Cabled Distortion at 85 dB SPL - 0.3% in midrange, about 3% at 70 Hz, still good:

Cabled Distortion at 95 dB SPL - above 1% at some frequencies, and low-frequency distortion will be audible, but still well under control for this high volume level:

Harmonic Distortion - Cabled:
L @ 75 dB SPL = 0.42% @ 100 Hz, 0.25% @ 2 kHz
R @ 75 dB SPL = 0.35% @ 100 Hz, 0.50% @ 2 kHz
L @ 85 dB SPL = 0.82% @ 100 Hz, 0.17% @ 2 kHz
R @ 85 dB SPL = 0.40% @ 100 Hz, 0.23% @ 2 kHz
L @ 95 dB SPL = 2.2% @ 100 Hz, 0.46% @ 2 kHz
R @ 95 dB SPL = 1.2% @ 100 Hz, 0.29% @ 2 kHz

IM Distortion (DIN) - Cabled:
L @ 75 dB SPL = 0.34%
R @ 75 dB SPL = 0.40%
L @ 85 dB SPL = 0.62%
R @ 85 dB SPL = 0.87%
L @ 95 dB SPL = 2.1%
R @ 95 dB SPL = 3.0%

Harmonic Distortion - Bluetooth - dB Below Clipping:
L @ -30 dB (75 dB SPL) = 0.42% @ 100 Hz, 0.25% @ 2 kHz
R @ -30 dB (75 dB SPL) = 0.35% @ 100 Hz, 0.50% @ 2 kHz
L @ -20 dB (85 dB SPL) = 0.82% @ 100 Hz, 0.17% @ 2 kHz
R @ -20 dB (85 dB SPL) = 0.40% @ 100 Hz, 0.23% @ 2 kHz
L @ -10 dB (95 dB SPL) = 2.2% @ 100 Hz, 0.46% @ 2 kHz
R @ -10 dB (95 dB SPL) = 1.2% @ 100 Hz, 0.29% @ 2 kHz

IM Distortion (DIN) - Bluetooth - dB Below Clipping:
L @ -30 dB (75 dB SPL) = 0.18%
R @ -30 dB (75 dB SPL) = 0.38%
L @ -20 dB (85 dB SPL) = 0.36%
R @ -20 dB (85 dB SPL) = 0.52%
L @ -10 dB (95 dB SPL) = 0.77%
R @ -10 dB (95 dB SPL) = 1.4%

Harmonic Distortion - Amplified:
L @ 85 dB SPL = 1.4% @ 100 Hz, 0.13% @ 2 kHz
R @ 85 dB SPL = 0.50% @ 100 Hz, 0.16% @ 2 kHz

Impulse and Step Response: Very clean and fast for dynamic headphones. Cabled mode is slightly susperior to Bluetooth, Amplified mode is the worst of the three, but still quite good.

Group delay:

Impedance: Driver impedance matching is good, easy to drive from a low source impedance.

Maximum input level @ TX4 input before clipping, TX4 transmitter to S1 headphone:
0.418 Vrms

Other Factors - not part of the Overall Performance Score

  • Reference headphone: Yes.
  • Drivable with portable media devices: No, but ALMOST. My standard is to reach 90 dB SPL with a loud track from a typical smartphone or tablet, and the S1 fell just short of that. If you listen at moderate levels, they will satisfy you, but if you are hoping to use them to split atoms - or blast at very high volumes - from your i-/Android device, the S1 might not do the job.
  • Isolation: __ dB, not as much as my other sealed 'phones. On an airline trip, the person next to you is going to hear your tunes pretty clearly at higher play levels.
Pendulumic Stance S1 Evaluation Scores

  • Imaging: 8.0
  • Soundstage: 9.0
  • Clarity: 8.5
  • Speed: 9.0
  • Frequency Response: 9.6 (Flat Profile)
  • Overall Listening Experience: 10
  • Comfort: 9
  • Design: 10
  • MSRP/Street: $199/$199
  • Overall Performance Score: 9.4 out of 10
In Summary

Ah, the convenience of not having a cable to deal with, that can spoil you really fast. Being a long-time headphone user, there is a natural time to deal with the cable response tbat one is conditioned to expect with putting a set of 'phones on, moving around much, taking them off, and I experienced numerous little moments of joy with Bluetooth freedom. I found myself looking for opportunities to use the Stance S1 headphones just because it was fun, and sounded that good.

The Stance S1 might become my travel headphone of choice (keeping the volume down for fellow passengers' sake), they are that versatile and perform that well in every category. And, having tried numerous sets of headphones proported to be "reference" quality sealed headphones, they are the closest I have found without spending at least twice the money.

Audioengine B1 Premium Bluetooth Music Receiver

The Audioengine B1 is a high-fidelity receiver that easily allows you to stream music from a Bluetooth-enabled smartphone, tablet, or computer into your music system. The tough little unit has an aluminum case with attached swiveling antenna and 3-stage redundant power regulation to keep noise to a minimum. The B1 supports A2DP (of course), and aptX for true CD-quality sound. Included are an RCA hookup cable, power supply, a microfiber bag for taking the B1 on walkabout - it is certainly small and light enough to consider portable - and a setup guide. The B1 has stereo-RCA outputs and a TOSLINK digital optical output.

A single push button and a single indicator LED on the front panel provide all the operator input and output for the unit. This is fairly common in Bluetooth devices, and can be perplexing until you get the hang of an individual unit's operating sequences. Luckily, there are Bluetooth profiles that simplify the way transmitters and receivers interact, and much of the time they figure out what to do and work in spite of the operator's confusion.

The B1 uses the AKM AK4396 D/A converter, an upsampling converter with 24-bit 48-kHz capability. All signals regardless of bit depth are upsampled to 24 bits. Input data rate is determined by the source material, the source device, and the Bluetooth protocol. The digital output always operates at 24-bits / 48-kHz. Noise and distortion specs are exemplary, better than my ability to measure, and were verified by my listening tests.

Much of what has been said previously applies directly to the B1. Technology-wise, it must be paired with an aptX-capable source for it to sound its best. There are no settings involved in making this happen. As two devices "pair," they determine common capabilities and enter the right modes automatically. With an aptX source, the B1 cranked out CD-quality sound as advertised.

Most of the testing in the High Fidelity Comes To Bluetooth section above directly involved the B1. My tests verified that the B1, when paired with an appropriate source, did indeed deliver audio quality virtually indistinguishable from the CD source file. In my listening tests I found I had a slight preference for the digital output into my audio interface vs. the analog output, but that might well have been because the latter involved an extra set of D/A and A/D conversions. The difference was a minor subtlety at best.

Latency is stated to be 30 mS, but the B1 specs do not state that it is aptX Low Latency capable. And when paired with my aptX Low Latency-enabled transmitter, I measured 210 mS of latency, so audio-video sync issues must be considered in applications where they matter.

I found the B1 extremely simple to operate - just pair it with another unit and it runs. It was completely dependable, never locked up or misbehaved, never produced any mysterious pops or clicks. It is a well-behaved little unit, always doing what you expect of it, or better.

An operating range of up to 100 feet is claimed. As mentioned before, none of my transmitting devices could come anywhere close to delivering on that promise, but there are higher-powered transmitters available which would give better distance performance.

The Audioengine B1 Premium Bluetooth Music Receiver gave a solid CD-quality performance in all of my testing, is easy to use, looks sharp, and should last a good long time, even getting carried around and beat up a bit. There are less-expensive receivers out there, but when you consider build quality, durability, and all that Audioengine has done to ensure pristine high-fidelity audio into your sound system, the B1 ends up looking like a solid buy. It is a worthy addition to the serious audiophile's system.


Audioengine B1 Premium Bluetooth Music Receiver

  • Bluetooth receiver type = Bluetooth 4.0 audio with aptX codec
  • Supported Bluetooth profiles = aptX, A2DP, and AVRCP
  • Inputs = Bluetooth
  • Outputs = Stereo analog RCA, Digital optical (SPDIF)
  • Required power = 5V, 200mA
  • Operation range = up to 100ft (30m) typical
  • Full-scale output 2.0V RMS
  • Output impedance = 57 Ohms
  • D/A converter = AKM AK4396
  • Power filtering = 3-stage redundant regulation
  • SNR (DC to 20 kHz) = >100dB
  • THD+N (1 kHz FS 96 kS/s) = <0.02%
  • Frequency response = 10Hz - 20kHz (+/-0.5dB)
  • Crosstalk = >-86dB
  • Input bit depth = 24-bit (upsampled)
  • Input data rate = Determined by Bluetooth
  • Latency = 30 milliseconds (ms)
  • Product dimensions = 3.5 x 4.0 x 1”
  • Includes built-in AKM4396 DAC for superior 24-bit upsampled playback
  • Aluminum case with audiophile-grade connectors
  • Analog and optical outputs
  • 2.0Vrms maximum output level
Miccus Mini-jack TX4 Wireless Bluetooth 4.0 Music Transmitter

The Miccus Mini-jack TX4 Wireless Bluetooth 4.0 Music Transmitter features the aptX Low Latency codec and supports two connections simultaneously. Its form factor is not what you might go looking for to add to your high-end audio system of home theater, but there is not much available yet that is small, Bluetooth 4.0, and aptX capable, including the Low Latency designation. Throw in dual transmission streams, and the TX4 fills a niche with little competition to date. It comes with an extension audio cable and a USB charging cable.

As with the other devices reviewed, the TX4 is a one-button, one-LED device. Operation is simple, though, and the Bluetooth pairing and connecting sequences are generally seamless enough that you will rarely need to refer to instructions. I did run into connections that I did not expect. "Now there is no sound from my tablet, why is that? - Oh, the TX4 is connected to it, too." I got in the habit of disconnecting a device and then turning Bluetooth off when using my tablet just to help eliminate the unexpected. Most users will not need to go to this trouble, but beware of the possibility.

As with previous discussions, the TX4 sent out CD-quality music when appropriately paired. It also operated cleanly and predictably. As indicated in the High Fidelity Comes To Bluetooth section above, it reliably transmitted CD-quality audio when appropriately paired.

Distances of up to 45 feet are specified, but this is most likely an echoing of Bluetooth technology capability, not tested performance level. My 25-foot limit involved a line-of-sight connection between the TX4 and both the B1 receiver and the S1 headphones, so that is the maximum one should expect from this tiny unit with its internal antenna. At that point dropouts began to occur, a fraction of a second long but annoying enough that you would not stretch that distance limit.

Battery life of 10 hours per charge is specified, though I never came close to running out of battery power. I tried running with USB power connected but hum was introduced. This was probably due to a ground loop resulting in my system and might or might not be typical.

The TX4 is small, weighs almost nothing, and of the units tested was the only one that I worried about damaging. I always used the extension audio cable so I did not have to force the rotating plug on the TX4 itself into a tight jack on my phone or tablet. A 1/8" stereo jack to dual 1/4" plug converter cable came in handy to run the TX4 with my audio interface. But even though the unit seems vulnerable, it endured my testing, although it never received any rough treatment. And it is intended for portable use, so who can complain about it being small and light?

The form factor might not be what you are looking for, as it was not initially for me, but its portability is a real plus. I grabbed it to round out the review and have on hand for... whatever. It will probably be replaced at some point by a higher-powered transmitter with similar capability and become a knock-around unit.


Miccus Mini-jack TX4 Wireless Bluetooth 4.0 Music Transmitter

  • Bluetooth v4.0 with APT-X Low Latency
  • Operating Range = 45 ft. (14m)
  • Frequency = 2.4 GHz
  • Bluetooth stereo profile = A2DP
  • Sleep mode for power conservation
  • Power supply = Charges via Micro USB cable
  • Operation Time = Up to 10 hours per charge or continuous when connected to USB power
  • Weight = 0.8 ounces
  • Dimensions = 2.8 x 0.8 x 0.6 inches
  • Batteries = 1 Lithium ion battery required (included)

While Bluetooth is not about to replace cables or TOSLINK as a way to move critical audio around your room or facility, it is ready and able to deliver 16-44 and 16-48 quality sound from mobile devices and into headgear. And as aptX Low Latency and aptX Lossless devices become more available, they will be worthy of performing more and more hi-fidelity chores in your movie/listening room without cables.

The Pendulumic Stance S1 Wireless Headphone is a must-audition piece of audio gear for the serious listener who wants solid - no, make that downright excellent - listening performance in Bluetooth-enabled headphones. The S1 is an all-around great pair of 'phones for the money, with the added benefit of true CD-quality cordless freedom.

The Audioengine B1 Premium Bluetooth Music Receiver is the perfect device for the discerning listener who has multiple media-capable Bluetooth-enabled devices in his life - who does that NOT include? - and wants the convenience of pair them and play rather than digging for and tripping over cables. When a guest drops by with hot new tunes to play for you, you say, "Pair it up with my B1 and let's hear them." Simple as that!

The Miccus Mini-jack TX4 Wireless Bluetooth 4.0 Music Transmitter is a big performer in a tiny, portable package.

Go to the Three Bluetooth Device Review Discussion Thread - Pendulumic Stance S1 Wireless Headphone, Audioengine B1 Premium Bluetooth Music Receiver, Miccus Mini-jack TX4 Wireless Bluetooth 4.0 Music Transmitter.http://www.hometheatershack.com

Go to the Headphone Roundup Overview for scoring and comparison details.

Pendulumic Stance S1 Wireless Headphone

Audioengine B1 Premium Bluetooth Music Receiver

Miccus Mini-jack TX4 Wireless Bluetooth 4.0 Music Transmitter


4,838 Posts
Discussion Starter #78

SVS Prime Tower Review

SVS Prime Tower: $499.99 each

by Wayne Myers


The SVS Prime Tower was introduced at Rocky Mountain Audio Fest in October. At $1000 per pair, the Prime Tower has a lot of competition in its class, speakers that are trying to sound like their more expensive bigger brothers. Some come close but most have flaws which hold them back, as is to be expected. A few really shine, seeming to break any rules about how much a speaker should cost to sound really good.

I got a good introduction to the Prime Towers at RMAF, resisting the impulse to move them around to optimize their setup, and asked for a pair to review in detail. The Prime Towers stood in the shadow of the SVS Ultra Towers, which I have heard several times and which, at $2,000 per pair, perform very well and leave big shoes for the Prime Towers to fill. The Ultra Tower also shows that the SVS engineers are able to make speakers that perform very well and give listeners a lot of value for their dollar.


The Prime Tower is a three-way bass reflex design with dual rear-firing ports. Drivers include two 6.5-inch woofers and a 4.5-inch midrange, all with polypropylene cones and cast ABS-fiberglass composite baskets, and a one-inch aluminum dome tweeter with diffuser. The two woofers cross over to the midrange at different frequencies - 165 Hz and 350 Hz - with different slopes, and the midrange and tweeter cross over at 2.1 kHz. The mid/tweeter crossover was especially well executed, invisible on measurement plots and smoothly integrated even at different listening angles. The available finishes are piano black or black ash. I received the piano black, which was expertly done.

The Prime Towers are compact, versatile, and VERY easy to place.

SVS Website.



SVS Prime Tower
Loudspeaker Physical Description:
  • Floor Standing Tower Loudspeaker
  • Black ash and piano gloss black finish options.
  • 5-way binding posts.
  • Dual 1.7” wide-flared rear-firing ports.
  • Cloth grille with pin/cup retention system.
  • Elastomer screw-in feet - adjustable for level.
  • Spiked metal screw-in feet included - adjustable for level.
  • Cabinet Dimensions: 36" (H) X 8" (W) X 10.8" (D).
  • Overall Dimensions: 36.6" (H) X 8" (W) X 11.6" (D) (includes grille, feet and binding posts).
  • Shipped Dimensions: 41.3" (H) X 14.1" (W) X 17.3" (D).
  • Weight Unboxed: 40.1 pounds.
  • Shipped Weight: 46.3 pounds
Driver Array and Technical Highlights:
1" aluminum dome tweeter:​
  • FEA-optimized diffuser delivers airy and unveiled presentation.
  • Aluminum dome for exceptional transient response.
4.5" midrange driver:​
  • Polypropylene cone for excellent stiffness/mass ratio and pistonic behavior.
  • Aluminum shorting ring to reduce gap inductance, lower distortion, and enhance high frequency response.
  • Cast ABS-fiberglass composite basket ensures precision component alignment and excellent thermal transfer.
  • Vented voice coil former minimizes air compression artifacts.
Dual 6.5" woofers:​
  • Long stroke motor ans suspension for high output.
  • Polypropylene cone for excellent stiffness/mass ratio and pistonic behavior.
  • Aluminum shorting ring to reduce gap inductance, lower distortion, and enhance high frequency response.
  • Cast ABS-fiberglass composite basket ensures precision component alignment and excellent thermal transfer.
  • Vented voice coil former minimizes air compression artifacts.
SoundMatch Crossover Network:
  • 3.5-way crossover with premium-grade capacitors, air-core inductors and heavy-trace printed circuit boards.
  • Tapered woofer array optimizes the transition to the midrange driver and reduces vertical axis lobing.
  • Midrange-to-tweeter crossover: 2.1 kHz (12 dB/octave slopes).
  • Top woofer (Combined Woofer) to midrange crossover frequency: 350 Hz (12 dB/octave slopes).
  • Bottom woofer low pass frequency: 165 Hz (customized filter Q and slope).
Cabinet Construction Technical Highlights:
  • Separate sealed midrange enclosure shifts standing waves beyond the driver pass band, improving sound quality.
  • Separate woofer enclosures with optimized port tuning frequencies for smooth and accurate bass response.
  • Acoustically transparent and FEA optimized grilles minimize diffraction.
  • Chamfered front baffle and flush-mounted drivers reduce edge diffraction and improved on-axis high frequency response.
  • FEA-optimized cabinet and bracing eliminates resonances.
Frequency Response and Electro-Acoustic Data:
  • Rated bandwidth: 30 Hz-25 kHz (+/-3 dB).
  • Nominal impedance: 8 ohms.
  • Sensitivity: 87 dB (2.83V @ 1 meter full-space, 300-3kHz).
  • Recommended amplifier power: 20-250 watts.
Associated Review Equipment

Measurement Methods
  • Asus G74SX Laptop, Intel I7-2670QM @ 2.2 GHz, 16 GB DDR3 Memory, Room EQ Wizard, foobar2000, Reaper DAW
  • Media Server, Phenom II x6 1055t @ 2.8 GHz, 8 GB DDR2 Memory, Room EQ Wizard, foobar2000, Reaper DAW
  • Roland Quad-Capture Audio Interface
  • M-Audio Firewire 410 Audio Interface
  • Beyerdynamic MM1 Measurement Microphone
  • American Recorder SPL-8810 Sound Level Meter
  • Onkyo TX-SR705 Receiver
  • Emotiva Pro Airmotiv 4 Powered Studio Monitors
  • MartinLogan ESL Hybrid Electrostatic Loudspeakers
  • Bosch DLR130 Laser Distance Measurer

Frequency response measured outdoors at 2 m on the tweeter axis.

In-room response at the Listening Position on the tweeter axis, zero listening angle. Mids and higs are unusually flat.

Total Harmonic Distortion at 75 dB SPL is well below 1% through the listening range.

Total Harmonic Distortion at 85 dB SPL is below 1% above 100 Hz.

Total Harmonic Distortion at 95 dB SPL has a distortion peak of 3% at 250 Hz for the speaker shown. It was 1.4% for the other speaker. Above 100 Hz most of the listening range is still below 1% distortion, except at 3 kHz where it peaks slightly above.

Impulse response. The pre-ringing indicates near-perfect brick-wall low-pass filtering in the Roland audio interface with high-frequency content approaching that filter limit. The jagged peaks as the impulse returns to zero and the jagged overshoot beyond might account for some of the lack of transparency noticed in listening tests. They appeared on indoor and reflection-free outdoor measurements.

Step response. Low-frequency ringing is pronounced and indicates less-than-ideal control of the woofers. I cannot say that this stood out in a way that concerned me - while bass dynamics were not super-tight, they never seemed muddy or mushy. The initial high-frequency "bounce" and the jagged areas in the first 20 mS indicate mid and high frequencies where clarity was somewhat less than desired. These step-response waveform features were present on indoor and reflection-free outdoor measurements.

Group Delay has peaks at 170 Hz and 310 Hz related to the crossover network. Phase shift is quite non-linear through this region. But tight component tolerances keep these curves almost perfectly overlaid between left and right speakers and soundstage and imaging performance were unaffected.

Impedance measurements again show very tight tolerances. The impedance curves are almost perfectly overlaid.

Polar Response measurements, taken indoors, gated, with 8 ms gate, normalized. Microphone was stationary, speaker was turned in 5 degree increments.

Initial Listening Test

The Prime Towers put their best foot forward quickly by performing a very thorough disappearing act in the first location where I set them up. They were a little close together, and I set with no toe-in. They sounded much bigger than their size, and projected quite an engaging soundstage regardless of the disadvantaged of their positioning. For my first listening session I left them right where they were.

At RMAF, I had noticed that one of the main differences between the Prime and Ultra Towers was the smoothness and transparency of the tweeter frequency range. The Ultra Tower tweeter sounded better each of the first three times I heard the Ultras over a six-month period, and I suspect that the engineers were refining its design along the way. Choosing to focus on high-frequency performance for a bit, I added a shelf filter with a gradual 5 dB rise starting at 2 kHz. The overly bright presentation was intended to emphasize any flaws or annoyances in the high-frequency range.

The first listening session made use of the Eels album Blinking Lights and Revelations from beginning to end, some songs repeated. Mark Oliver Everett's gravelly voice managed to trigger a couple of peaks in the upper range, but for the most part the Prime Towers were very listenable even with that range boost. They did a nice job of reaching into inner detail of the voice and instruments, and were quite clear and smooth overall.

On Trouble With Dreams, with sampled glockenspiel, the soundstage came alive with high, clear bells, a delightful surprise that was one of the highlights of my working with the Prime Towers.

The rest of the frequency range was managed very well in this setup, too. Drums and percussion sounds were tight and lively. Vocals and string instruments were accurate natural sound. Imaging was very sharp and specific.

Listening Angle Tests

Curious about how easily the Prime Towers were to place, I lined them up more carefully and spent time with them playing on-axis (zero-degree listening angle) and angled outward in 5-degree increments out to 30 degrees. The first and biggest impression was with how consistent the soundstage and imaging (SS&I) through these angles. Most speakers I have worked with in the class had a definite sweet angle or two where imaging locked in, and imaged poorly at any other angle. The Prime Towers defied all attempts to find an angle where the soundstage and image clarity were less than exceptional, and insisted on remaining invisible throughout the exercise, thoroughly disappearing wherever placed. I will mention that they had the advantage of a blank wall behind them, my ideal for soundstage development and imaging.

As the listening angle test proceeded, the soundstage opened more and more with each outward turn of the speakers. Imaging remained very sharp, softening slightly at the wider angles but only to a barely noticeable degree. This set of characteristics alone moved the Prime Towers for me into a class with few equals at anywhere near the price, a thoroughly impressive performance. I can think of competing speakers that I rejoiced with at finally finding a narrow sweet angle with adequate (SS&I) for an enjoyable listening experience. A pair of towers allowing so much flexibility and delivering first-rate spacial performance is really quite a gem. Expecting the new SVS family offering to be solid, I am really knocked out by what they delivered.

The upper-mid and high-frequency response seemed to smooth somewhat, with a few minor on-axis peaks that evened out with the widening angle. Overall frequency response was very consistent through those same angles. While far from ruler-flat, the range is free of annoying spikes and very listenable. One wish I had was that the 2.5 kHz presence peak at the bottom of the tweeter's range could be a decibel lower, softened just a bit. I verified this by temporarily applying a single parametric band filter with 1 dB of loss centered on the octave, and the result was just right.

B-52s, Revolution Earth - mono mix, Good Stuff, Vision Of A Kiss:
The mono mix of Revolution Earth is a good image sharpness test. With speakers that image poorly, it will sound stereo due to amplitude and time mismatching between the left and right sources. With tight imaging, the song is razor-blade narrow. With the Prime Towers, the song was sharp and stable. On the other B-52s tracks, a strummed acoustic guitar was punchy and focused, but depth acuity was lacking, the final quality of a soundstage which requires acoustical enhancement, which sometimes occurs by happenstance but usually requires some work. Bass lines and kick drum were solid, not super deep.

Eels, Baby Loves Me, Spectacular Girl:
Solid bass

Beth Nielsen Chapman, Beyond The Blue:
The deepest drums did not have the depth I remember. This is to be expected. Bass depth and maximum volume level are the main gains generally to be found as speaker prices go above $1000 per pair.

Radiohead, Weird Fishes, All I Need, The National Anthem:
The lead-in drumstick clicks were sharply focused. Glockenspiel samples also were precisely located and very clear. The dense jazz band did not distort or become congested.

Deerhoof, Fete d'Adieu:
A dense track, handled with ease, no sense of strain at high volume.

Porcupine Tree, Shallow, Way Out Of Here:
Heavy tracks, punchy snare drum that threatens to clip on every strike, dense metal guitars, all stayed clean and uncongested.

New Pornographers, Brill Bruisers, Fantasy Fools, Dancehall Domine, From Blown Speakers:
These tracks were mixed with a lot of midrange information. Here the Prime Towers were slightly lacking in transparency.

Michael Hedges, Eleven Small Roaches:
Nice definition, not super detailed on string plucks, but true tonality.

Other Observations

While SS&I performance from the SVS Prime Towers was exceptional, there was a slight lack of clarity that was not explained by distortion measurements, as though the music had a touch of graininess to it. This effect was minor but occasionally apparent at mid frequencies, especially on tracks with dense content in that range. When comparing the Prime Towers to an inexpensive speaker with a folded-motion tweeter, the difference in transparency was noticeable. While not a major issue, it did get my attention occasionally and must be mentioned. I doubt it would ever turn up in home theater use, and the many of the music tracks I listened to did not suffer from it, but dense vocal harmonies like the New Pornographers tracks became slightly hashy from the effect. The inner detail on the Michael Hedges acoustic guitar track was also affected.


The SVS Ultra Towers were a pleasant surprise. I was expecting a solid, somewhat utilitarian speaker that handled home theater and music tracks like a trooper, performing adequately but without finesse. But the SVS team has shown us that they intend to be thought of as serious loudspeaker makers. There is no doubt the Prime Towers are on a short list of models that should be considered by anyone with $1000 to spend on a pair of speakers.

I have emphasized two-channel application because of the (SS&I) performance, but SVS's per-speaker pricing indicates that they also aim for home theater front-mains business for the Prime Towers. Broad dispersion makes the compact towers simple as pie to place in a wide home theater with three- or four-wide seating. Anyone with a budget of around $500 per speaker for0 towers should look closely at the SVS Prime Towers. They do too many things right to be ignored.


4,838 Posts
Discussion Starter #79
AKG K 701 Headphone Review

AKG K 701 (MSRP/Street): $539 / $231

by Wayne Myers


The AKG K 701 Headphone, AKG's flagship headphone until being replaced by the K 812, is well-known for its flat frequency response. In some circles it is considered the flattest headphone available for mixing and mastering or as a portable frequency response reference.

AKG Reference Family

Following is a comparison chart of the current AKG Reference line, including the obsolete K601. Bass response is very flat (thank you, AKG) except for the latest additions, the K 712 and K 812, where AKG appears to have buckled to market pressure, while also extending the response to deeper limits. The K 601 had a midrange peak that was flattened for some models and changed to a dipped midrange response for others. Transient response is best for the K 7xx models, very ringy for the K601 and K812. Distortion was notoriously high for the earlier K 7xx models at higher listening levels, however. This was improved with the K 712 and K 812. Some models offer a detachable 3-wire cable, others a non-detachable 4-wire cable down to the 3-conductor termination plug, a slight advantage for soundstage and imaging performance. Some models make use of a hadband with supposedly padded ridges which I found a bit uncomfortable with extended use. The flat headband designated as "soft" seems more comfortable.

Comparison Table
No code has to be inserted here.

AKG K 701 Website


The K 701 is a true reference-class headphone, an open design with frequency response about as flat as one will find in a headphone. This will sonund bright to those used to the laid-back high end more commonly found in 'phones. But for those interested in a truthful headphone sound, it is one of a few reference headphones one can turn to with confidence.

The K 701 ear pieces are as comfortable as you will find. They completely surround the ear with no pressure on the ear itself, barely touching it in a few spots. The headband has padded ridges which could have been a lot softer. The contact points on top of my head become uncomfortable after awhile.

Transient response with the K 701 is quite good, with a bit of overshoot and some ringing dampening out in 1 ms or less. If there is a performance weakness in the design is probably the harmonic distortion at very high listening levels (above 90 dB average), which approaches 5% and can be heard on some vocals. This is not a big negative by any means, they have to be driven pretty hard to get to audible levels of distortion.

The straight cable is not detachable, and contains 4 wires allowing complete electronic separation until the common wires are joined at the ground of the termination plug. This improves channel separation slightly, giving better imaging and soundstage, which are very good with the K 701.

Associated Review Equipment

Measurement Methods
  • Asus G74SX Laptop, Intel I7-2670QM @ 2.2 GHz, 16 GB DDR3 Memory, Room EQ Wizard, foobar2000
  • Roland Quad-Capture Audio Interface
  • 3Dio Freespace Binaural Microphone, modified, custom HRTF correction curve
  • Mackie 402-VLZ3 Preamp/Mixer
  • American Recorder SPL-8810 Sound Level Meter
  • AKG K 601 Headphones
  • AKG K 701 Headphones
  • Beyerdynamic DT 880 Premium 250-Ohm Headphones
  • FiiO X3 Portable DAC/Headphone Amplifier/Media Player
  • OPPO PM-1 Planar-Magnetic Headphones, Courtesy OPPO, Home Theater Shack Sponsor
  • Sennherser HD 600 Headphones
  • Sony MDR-V6 Headphones
  • OPPO HA-1 DAC/Headphone Amplifier, Courtesy OPPO, Home Theater Shack Sponsor
Test Tracks


Listening Scores

Frequency response for the K 701 is as close to flat as you will find in a headphone, other than the K 812 (score=10.0/10). There is some peakiness at high frequencies that draws complaints among users, but I had a hard time even finding a track that drew it out. Those who shy away from brightness, and the majority of listeners will call flat response "bright," might shy away from the sound as being aggressive or pushy, but it is smooth and clean and I like it.

Imaging is excellent with the K 701 (score=9.5/10). At high frequencies it is tight and sharp. At mid frequencies is widens slightly, but remains stable and very good. The soundstage is wide and spacious and easily moves out of the head, very natural and lifelike (score=10.0/10).

Clarity is very good in spite of the previous mention of harmonic distortion (score=9.5/10). The complex tones making up cymbals and bells lost a little of their crystaline character on occasion and vocals could gain a bit of a harmonic edge, but only at high volumes. At normal listening levels the K 701 remain very clean and clear.

The Speed test is done with special tracks of fast pulses and sequences. The K 701 is not the fastest headphone around, but kept up with everything I threw at it without getting muddy or messy (score=9.0/10).

For the Overall Listening Experience, the K 701 gets 9/10, having no significant detractors for me. but not being as interesting as some headphohes, and not being ideal for extended listening. The presentation is detailed and accurate, good for hearing "what is really going on," but can wear on you after awhile.

Non-Listening Scores

The K701 gets 9/10 for Comfort and the same for Design. The only reason they do not get a perfect score for comfort is the headband's hard ridges. The earpieces are as comfortable as they can possibly be. They are light and stay on well. They are big, have no folding capability at all. They are a studio headphone, made for sound, not looks, yet are attractive anyway. While mine have lasted well with medium use over 4+ years, they have been babied, and the plastic loops and plastic stretch bands that tension the headband have always looked vulnerable to me.

Other Factors - not part of the Overall Performance Score

  • Reference headphone: Yes
  • Drivable with portable media devices: No, they do not reach 90 dB with a portable media player or smartphone.
  • Isolation (if closed design): n.a.

Specifications and Measurements

Measurement Graphs

  • Driver: Open-back headphones
  • Frequency Response: 10Hz - 39.8kHz
  • Maximum Input Power: 200 mW
  • Input Impedance: 62 ohms
  • Sensitivity: 105 dB SPL/V
  • Style: Over-ear
  • Sound: Reference sound
  • Connectivity: Wired
  • Smartphone control: No control option
  • Colour: White
  • Earpads: Replaceable 3D-Form
  • Headband: Exclusive leather self-adjusting
  • Cable: 3.00 m, straight
  • Connector: 3.5mm hard gold-plated jack plug and contacts
  • Weight: 235 g
  • Include Accessories: 6.3mm adapter
Frequency Response:

Distortion at 75 dB SPL - well below 1%.

Distortion at 85 dB SPL - approaching 1% at some frequencies, still very good.

Distortion at 95 dB SPL - above 1% at some frequencies, but well under control.

IM Distortion (DIN)
L @ 75 dB SPL = 0.29%
R @ 75 dB SPL = 0.30%
L @ 85 dB SPL = 0.35%
R @ 85 dB SPL = 0.40%
L @ 95 dB SPL = 0.64%
R @ 95 dB SPL = 1.1%

Impulse and Step Response: Very clean and fast for dynamic headphones.

Group delay:

Impedance: Driver matching is fair, impedance is consistent, easy to drive from any source impedance.


When it comes to headphones for accurate, straightforward listening or for mixing or mastering, there are few models that come out ahead of the AKG K 701. Their sound is flat and clean with terrific soundstage and imaging. No longer AKG's flagship model, they are available at street prices much lower than one would expect for the performance they deliver.

  • Imaging: 9.5
  • Soundstage: 10.0
  • Clarity: 9.0
  • Speed: 9.5
  • Frequency Response: 10.0 (Flat Profile)
  • Overall Listening Experience: 9
  • Comfort: 9
  • Design: 9
  • MSRP/Street: $539/$231
  • Overall Performance Score: 9.6 out of 10


4,838 Posts
Discussion Starter #80

Power Sound Audio MTM-210 Speaker Review

PSA MTM-210: $799.50 each

by Wayne Myers


The Power Sound Audio MTM-210 is a recently introduced audiophile speaker from the Mineral Ridge, Ohio based speaker and subwoofer manufacturer. While the company's target market is primarily home theater enthusiasts, the MTM-210 caught my attention as an offering poised to cross into two-channel territory, and I was anxious to hear what co-founders Tom Vodhanel and Jim Farina had come up with. The two questions in my mind were:
  • Could the MTM-210 really be considered an audiophile speaker? and...
  • How well would it perform relative to other speakers in the under-$2000-per-pair price range?
I was also looking forward to working with a different speaker configuration, and there is much that is atypical about a speaker like the MTM-210, including the horn-loaded compression tweeter and the symmetrical Midrange-Tweeter-Midrange (MTM) design, and its high efficiency. There were several impressive examples of horn-loaded tweeters at Rockie Mountain Audio Fest in Denver last fall, and I have been open to new possibilities.


The PSA MTM-210 is a two-way sealed-cabinet design intended for use with a subwoofer. Drivers include two 10-inch woofer/midrange cone speakers and a 1-inch compression driver loaded with a cast aluminum exponential horn. The custom crossover is an in-house design.

The enclosure design is a straightforward box made of 3/4 inch MDF with a black spray-on covering material called CHEMTHANE 7030 - a fast cure, 100% solids spray polyurethane "for protecting wooden enclosures, audio speakers and other fragile substrates from damage during everyday use, freight loading personnel and exterior exposure." The coating has a textured vinyl-like feel that seems super-tough. It is specified for thin film applications of 15-30 mils, and it felt like a thick application had been used on the MTM-210.

Each unit's 55 lb weight tells you that construction involves some mass. A look through a woofer/mid driver opening confirms it. Inside the enclosure there are two bracing baffles which divide the unit into thirds at the levels between drivers.
Each is an mdf board glued to front, rear, and sides, routed-out leaving two beefy cross beams for extra strength.

The look is utilitarian, and some might get the impression that the MTM-210 is an over-simplistic or less-than-mature design. As for their appearance, many will end up in dark rooms or even behind projection screens and the home theater crowd tends to be flexible about a speaker's visual aesthetics. Two-channel enthusiasts often set the cabinet finish bar a bit higher, and might consider the appearance a deal killer for their listening rooms. Fair enough. But if there is any tendancy to surmise from the model's appearance that the MTM-210 is an unsophistocated sonic performer, be advised that they possess some special qualities worth taking the time to witness first hand. These are serious speakers, period, and I predict that there will be numerous audiophiles bending their speaker-appearande rules to accommodate an MTM-210 pair in their setups.

I expressed my interest in reviewing an MTM-210 pair with a 2-channel emphasis in mind, knowing that Todd Anderson of HTS was already giving them a home theater workout, and did not hold back on demanding the best performance from them.

PSA MTM-210 Web Page.



Power Sound Audio MTM-210
  • 2 way, audiophile loudspeaker
  • 1" titanium compression driver
  • Cast aluminum exponential horn
  • Dual 10" high efficiency woofers
  • Audiophile grade crossover completely designed in house
  • Frequency Response = 70Hz - 20kHz
  • Sensitivity = 98dB 1W/1M
  • Size HxWxD = 28" x 11" x 16" (includes grill)
  • Weight = 55 lbs

Associated Review Equipment

Measurement Methods
  • Asus G74SX Laptop, Intel I7-2670QM @ 2.2 GHz, 16 GB DDR3 Memory, Room EQ Wizard, foobar2000, Reaper DAW
  • Digital Audio Workstation, Phenom II x6 1100t @ 3.5 GHz, 16 GB DDR2 Memory, Room EQ Wizard, foobar2000, Reaper DAW
  • Media Server, Phenom II x6 1055t @ 2.8 GHz, 8 GB DDR2 Memory, Room EQ Wizard, foobar2000, Reaper DAW
  • Roland Quad-Capture Audio Interface
  • M-Audio Fast Track C600 Audio Interface
  • M-Audio Firewire 410 Audio Interface
  • Beyerdynamic MM1 Measurement Microphone
  • miniDSP UMIK-1 Measurement Microphone, Courtesy miniDSP, Home Theater Shack Sponsor
  • American Recorder SPL-8810 Sound Level Meter
  • OPPO HA-1 DAC/Headphone Amplifier, Courtesy OPPO, Home Theater Shack Sponsor
  • Lepai LP-2020A+ Tripath Class-T Audio Amplifier
  • Onkyo TX-SR705 Receiver
  • OSD Audio ATM-7 Digital 7-Zone Dual Source Speaker Selector with Remote Control
  • MartinLogan ESL Hybrid Electrostatic Loudspeakers
  • Bosch DLR130 Laser Distance Measurer
  • Fluke 77 Multimeter

Frequency response measured outdoors at 1 m on the tweeter axis - very flat above 1 kHz, slightly light in the midbass and bass range, very smooth throughout.

The unsmoothed responses shows freedom from lone sharp peaks that can resonate or cause fatigue. The narrow notches at 200 Hz and 1 kHz were consistently seen regardless of fine mic re-positioning, but were never audible in listening tests.

Frequency response measured outdoors at 1 m at 45, 90, 135, and 180 degrees off axis, showing the overall highly directive nature of the horn-loaded tweeter.

In-room response at the mid-field LP, 15 degree listening angle. The slight de-emphasis below 400 Hz is barely noticeable when you look for it, and quickly forgotten. Overall response is very smooth. The Moving Mic Measurement method (with pink noise) verifies the average response through the listening area to be very flat.

Relative driver contributions.

Polar response in the off-symmetry direction at a distancee of 3 ft indicates significant variation with small angle changes. An MTM-210 lying on its side will not sound so great to off-center listeners. PSA sells a version with the tweeter rotated 90 degrees which should perform much better in a horizontal center channel application. A user can make the change at home with a Philips screwdriver in a few minutes.

Polar response in the on-symmetry direction at a distancee of 3 ft stays very flat to well above 10 kHz.

Total Harmonic Distortion at 75 and 85 dB SPL is very low, well below 0.5%, and stays below 1% even at 95 dB SPL volumes.

IM distortion is also very low.

IM Distortion (DIN)
@ 75 dB SPL = 0.29%
@ 85 dB SPL = 0.31%
@ 95 dB SPL = 0.45%

Impulse response indicates speedy responsiveness and fast recovery. The ringing is at about 15 kHz. I wondered if it might contribute to lack of clarity on dense program material, but found no indications of this being the case. When A-B comparing to my reference electrostatics, I found a few passages where the MTM-210 could not quite keep pace with electrostatic clarity at higher volumes. This was rare and I really had to hunt for it. The MTM-210 performed with exceptional clarity.

Step response plots indicate the very definition of tight bass.

Group Delay varies only slightly, supporting the tight imaging and excellent soundstage capabilities of the MTM-210.

Impedance measurements show very tight tolerances. The impedance curves are almost perfectly overlaid.

A Comment On Setup Precision

We think of highly directive speakers like monopoles and dipoles as making room characteristics less important, as having an ability to "tune out" the room and work more directly with the listener, making room placement and treatments less important. This is true, but getting it to happen is not necessarily an easy task. I was reminded while working with the MTM-210 what a difference careful attention to detail can make in the setup process. This is true of all speakers, but the need for precision is accentuated with high-directivity speakers. More than once in the review process, I had to stop listening because something was off. Invariably, it was a little difference in angle or distance that was to blame, and a small adjustment corrected the problem.

The reader is reminded that these comments about the need for placement precision are characteristic of horn-loaded and high-directivity speakers in general and say nothing negative about the MTM-210 themselves.

I found it necessary to accomplish the following to get the best from the MTM-210:
  • Speakers at equal height.
  • Tweeters at ear level - sturdy stands are a must.
  • Speakers standing straight up, or if angled, speaker faces at the same angle and sides perpendicular to the floor.
  • Equal distance from tweeter to the center of the Listening Position (LP).
  • Matching Listening Angles.
...and where possible, remembering that the midrange drivers do not share the highly directive characteristics of the tweeter, and are responsible for some of the frequencies involved in good soundstage and imaging:
  • Matching toe-in.
  • Matching distance from front wall, if at all possible; if not, treatment may be needed.
  • Matching distance from side walls, if at all possible; if not, treatment may be needed.
How good is good enough? I got superb results with:
  • Distance matching to 1/4 inch.
  • Angle matching to 1/4 degree.
MTM-210 Placement And Sonic Characteristics

Position - Front-Wall Location
  • 92 in speaker plane to LP
  • 59 in speaker to speaker
  • 18 in speaker plane to front wall (2 in min back of speaker to wall)
  • 18 degrees toe in
  • 0 degrees off-axis listening angle
Position - Mid-Field Location

  • 60 in speaker plane to LP
  • 59 in speaker to speaker
  • 50 in speaker plane to front wall
  • 10 degrees toe in
  • 14 degrees off-axis listening angle
High-efficiency speaker designs - the MTM-210 weight in at 98 dB sensitivity - have a couple of special things going for them:
  • They are easy to drive, so low-powered amplifiers generally have plenty of headroom and can drive them with ease and without fear of even occasional clipping events.
  • Power dissipation is minimal so driver and crossover components stay cool and operate more linearly than with conventional speakers.
Once properly set up, it is hard not to notice the dynamic delivery by the MTM-210. Energy focus and efficiency combine to produce a delivery that is lively, often sounding like it is being performed live. This is a highly addictive quality in a loudspeaker. Also conspiring to make this liveliness possible are components carefully chosen for low distortion, always operating in their ideal thermal range due to low power dissipation. Power amplifiers never have to work very hard and operate in the cleanest part of their dynamic range. These factors work together to make delivery sound especially easy for high efficiency speakers.

The MTM-210 soundstage is more focused than with a conventional tower speaker. It all tends to appear along the tweeter-to-tweeter line between the speakers, perhaps seeming less spacious vertically but having more impact and being truer to life.

The MTM-210 may seem to produce an overall soundstage that is less spacious than from conventional speakers. This results from its directive nature, and from being less room-dependent at high frequencies. But there is nothing second rate about the soundstage and imaging (SS&I) produced by the MTM-210. If anything it ends up having stonger depth acuity, a quality difficult to achieve and highly room dependent with conventional speakers. Soundstage spaciousness will result more from later reflections in the room then early ones, giving even stronger support to sharp imaging, so easily disrupted by the earlier-arriving reflections typical of conventional speakers.

The tight soundstage line between tweeters makes vertical alignment of a left-center-right trio of MTM-210 speakers important in a home theater setup. Sounds or voices traveling from left to center to right will be likely to appear to move vertically if the tweeters are not on a straight line.

The MTM-210 absolutely excel close to the front wall, where they will usually be placed in a home theater. Many speakers do poorly near the front wall, even far more expensive models, usually sounding muddy and giving fair-to-pour SS&I results. The sealed design and 70 Hz cutoff are key to this performance. The MTM-210 produced some of the tightest bass I have heard from a speaker at any price, defying all attempts to get them to misbehave. The soundstage they projected in this position virtually erased the end of the room and the speakers as well. Imaging was tight and precise in all three dimensions, making instruments and voices sound as live as I have heard them in my room.

At this distance from the listening position (LP), image position stayed rock steady as I moved to the left and right home theater seating positions, 36 inches either side of the main LP. If ever a speaker could project a phantom image stable enough to not require use of a center channel speaker, the MTM-210 is the one to do it.

Out into the room in a mid-field configuration, the MTM-210 benefited from a more open 15 degree listening angle. Speakers were invisible in the soundstage, which if anything seemed more spacious than when set close to the wall. Imaging remained precise, although at this position the center image did shift somewhat with the listener's change of position. Not a problem in my book, with two-channel listening tending to be a solitary experience anyway. That 15 degree off-axis angle involved zero sacrifice in high-frequency response, the off-axis response remaining flat to well beyond 10 kHz. The SS&I performance had a great deal to do with the MTM-210 delivery of detail, also, as smaller image elements were better separated and stood out more clearly in the sound field.

Do they sound like horns? Of course it is inevitable that a horn-loaded tweeter will activate a listening room differently than any other kind of tweeter, so yes, in a sense it does sound different. But the MTM-210 compression tweeter with exponential horn displayed no overt resonance or signature that said horn-loaded tweeter at work. And, while lacking the complete invisibility of a perfect tweeter, it was rare that anything about its delivery would draw any attention to itself. I immersed myself in fun listening mode for hours with only an occasional pull toward analytical mode to address a question about MTM-210 sonics, and that is very good for any pair of speakers in this price range.

The delivery is very direct, again by nature of the design, and may seem more "in your face" than some listeners like. For those who like an impactful presentation and lots of clean detail, the MTM-210 delivers it all with ease, and can entertain for hours on end without fatiguing.

MTM-210 Listening Tests

Perfect World, Holding On For Life - Broken Bells:
Starting with Perfect World, I felt one of those rushes that lets you know that a pair of speakers is going to be a lot of fun to work with. Perfect World, Perfect Speakers? Well, that might be a stretch, although no obvious flaws were coming to attention, either.

Highs extended smoothly clear out to 15 kHz, bordering on bright, but smooth and clean. Kick drums were tight and punchy, while lacking in real depth. The MTM-210 is meant for use with a subwoofer and would work well with an 80 Hz or 70 Hz crossover. The low-frequency response below 400 Hz steps down slightly, as indicated in both outdoor and listening room measurements, but this never felt like a weakness. I did add a sub to hear the difference it made. By "add" I mean I plopped it down and spent about 5 minutes adjusting level and delay, a minimalist integration effort, but that was all it took to realize what was missing of the lowest frequencies. No doubt most listeners will want that last two LF octaves filled in somehow.

I mentioned the dynamic nature of the MTM-210, and of high-efficiency speakers in general, especially involving horns. Their directivity helps erase the room and tunnel from the speaker plane to the listener's ears directly. Instruments sounded more live than usual. Detail was uncovered and presented to be appreciated and enjoyed. Guitar notes had me seeing and feeling the scratchy pluck of the pick and the jump of the string.

At one point in this session I made a minor move to one speaker which resulted in the right being pointed ever-so-slightly higher than the left, a barely noticeable amount. I heard the mismatch before I saw it - image clarity and soundstage were off, the sound in general lacked clarity and the high-frequency smoothness had some resonant peaks sticking out, all of which might have one taking distortion measurements or looking for a defective amplifier or preamp or an incorrect setting - SOMETHING that needed fixing. Restoring the symmetry of the vertical aiming was all it took.

Along with the sharp, clean imaging and natural soundstage, the dynamics were also quickly obvious, especially on the drums, but all parts of the recording benefited from it.

From Blown Speakers - New Pornographers:
The drums stood out on this track, sounding much closer to live than usual, and I have heard this song a LOT recently. The empty areas of the soundstage outlined and highlighted the vocals and instruments.

Fantasy Fools - New Pornnographers
On some speakers the dense chorus vocals manage to sound grainy and unclear. With the MTM-210 they stayed clean.

Revolution Earth (custom mono mix) - B-52's:
This full-range track has been mixed to mono as an image clarity test. The image was like a golf ball, small and sharp.

Revolution Earth (original stereo mix), Ain't It A Shame, Good Stuff - B-52's:
Thoughtfully recorded tracks like these are like a layered dessert, with details to be discovered as you dig into it, with rich guitar and synth tones to appreciate, and with tight imaging and well-separated soundstage elements to explore.

Baby Loves Me, Spectacular Girl - Eels:
Crisp percussion elements sounded and felt live. The dynamics on these straightforward tracks felt like they had been through a "punch enhancer."

You Shook Me All Night Long - AC/DC:
AC/DC's simple recordings sounded like hearing the band live on the MTM-210.

My Own Summer, MX - Deftones:
Played at a louder volume level, these tracks sounded and felt like attending a Deftones concert, which I have done. The sizzle and punch of live music were delivered by the MTM-210 pair effortlessly. Where some speakers have ways of reminding you that they are working hard, the MTM-210 made it sound so easy.

Eleven Small Roaches - Michael Hedges:
The playing noises of this acoustic guitar track immerse the listener in the physical aspects of guitar performance. I can see the MTM-210 being favored by musicians for their ability to open up performance details.

Collapse The Light Into Earth - Porcupine Tree:
The strings on this track can sound shrill and lose clarity on a lot of speakers. They took on the slightest edge during the louder passages, but far less than with most speakers I have auditioned.

Weird Fishes--Arpeggi - Radiohead:
A great imaging test, the four lead-in drumstick clicks were precisely located and sounded live.

Packt Like Sardines In A Crushd Tin Box - Radiohead:
The punchy kick drum, like an impulse signal, stayed tightly focused. Each pulse was there and gone with no hangover.

Pyramid Song - Radiohead:
Another great imaging test, every cymbal strike was precisely located.

Variations on a theme of Corelli - Scott Davie - Rachmaninoff:
This track is recorded with more dynamic range than most. From pianissimo to fortissimo, the Overs piano tones were reproduced faithfully, and the live piano feel was evident.

Additional Observasions

As an experiment, I wanted to hear the benefit of slightly lifting the frequencies below 400 Hz to a flat level. Adding a single shelf filter in my music server at 300 Hz with 3 dB of boost (ReaEQ plugin, Low Shelf, 300 Hz, +3 dB, BW=1.2), this raised low frequencies to just the right level to give kick drums and bass lines a solid sense of authority without muddying the midbass tones. That is the only EQ I would use with the MTM-210, preferring to apply it minimally to bring out the best in a speaker rather than overwhelm it.

Listening with that touch of bass boost made even clearer the conciseness with which these speakers handle low frequencies. The MTM-210 delivers the very definition of tight, responsive, articulate bass, as good as I have heard.


In answer to my initial questions, the Power Sound Audio MTM-210 is clearly a solid entry in the ranks of audiophile speakers, and it stands tall as a serious performer at its price point, even raising the bar in a few measurement categories. With its concise bass, its crisp, extended, detailed highs, and its room-erasing soundstage and imaging capabilities, the MTM-210 deserves consideration by both home theater and two-channel listeners.

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