Axiom Audio LFR880 Floorstanding Speakers and ADA-1250 Power Amplifier Review - Home Theater Forum and Systems - HomeTheaterShack.com

 
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Axiom Audio LFR880 Floorstanding Speakers and ADA-1250 Power Amplifier Review

Axiom Audio LFR880 Floorstanding Speakers and ADA-1250 Power Amplifier Review








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



Introduction

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.


Description

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.


Specifications

Specifications
LFR880 Speaker
Enclosure Triple Vortex / Reflex
Max Amp Power 400 Watts
Min Amp Power 10 Watts
Freq Resp 31 Hz – 20 kHz +/-3dB
Freq Resp 25 Hz – 20 kHz +3dB / -9dB
Impedance 4 Ohms
SPL in Room 92 dB @ 1w/1m
SPL Anechoic 88 dB @ 1w/1m
X-Over 160 Hz & 2.3 kHz
Bi-Wiring Upper - Mid/Tweeter
Lower - Woofer
Tweeter 4 x 1"
Midrange 4 x 5.25"
Woofer 2 x 6.5"
Size 39.5" H x 9.25" W x 17" D
1003 mm H x 235 mm W x 432 mm D
Weight 62 lbs each
28 kgs each
DSP-1 Digital Signal Processor
Max Output 2Vrms
Gain Unity
THD <0.008% @ 1Vrms
Signal to Noise Ratio 102dB
(Input shorted, 22Hz-20kHz,  
un-weighted, Ref. 2V)  
Digital Conversion 24-bit,
Sigma-Delta ADCs and DACs
@ 96kHz Sampling Rate
Power Consumption 13W
RCA Input Single Ended
High Level Input
AC Input Voltage 115 or 230 (chosen when ordered)
Size 3.5" H x 17.75" W x 16.75" D
88 mm H x 450 mm W x 425 mm D
Weight 27 lb
12 kgs
ADA-1250 4-Channel Power Amplifier
Max Output per Channel 8 Ohms 4 Ohms
(RMS watts with distortion below 1%,  
measured 20 Hz to 20 kHz)  
One Channel Driven 225 W 450 W
Two Channels Driven 225 W 450 W
Three Channels Driven 225 W 416 W
Four Channels Driven 225 W 312 W
Voltage Gain 29dB
Sensitivity (Full Power into 8 ohms) 1.5 volts
Capacitance 108,000uf
Frequency Response (6 ohms, -3dB) 1Hz - 45kHz
Signal to Noise Ratio 103dB
(Input shorted, 22Hz-20kHz,  
un-weighted, Ref. full power @8ohms)  
RCA Input Single Ended
High Level Input
XLR Input Balanced
High Level Input
12 Volt Trigger Yes
AC Input Voltage 115 or 230 (chosen when ordered)
Size 5.25" H x 17.75" W x 16.75" D
88 mm H x 450 mm W x 425 mm D
Weight 58 lb
26 kgs


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

Measurements

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.
Note: These are the results in my listening room, and according to my personal listening preferences. The Far1 and Far2 settings might give excellent results under different conditions.
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 fins 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.



Conclusions

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.


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