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MartinLogan ESL Speaker Review

MartinLogan ElectroMotion ESL Speaker Review




MartinLogan Website
EM-ESL MSRP: $2,195 Pair
Available at your Authorized
MartinLogan Dealer



by Wayne Myers


Introduction

The MartinLogan ElectroMotion ESL (EM-ESL) is the company's entry-level hybrid electrostatic loudspeaker. The EM-ESL and its big brother, the Montis, are the first electrostatic speakers I have reviewed. While I received the EM-ESL first, I had the opportunity to spend time with Sonnie Parker's new Montis speakers back in January, and completed that review first. I will reference that review from time to time, having covered a lot of detail about the technology and MartinLogan's product characteristics there.

Martin Logan has been making electrostatic speakers since the early 1980's. Current models make use of a curved electrostatic panel, which has a wider horizontal radiation pattern than a typical flat-panel speaker. They also stick to the hybrid design for all but their largest model, that approach being the best for low-distortion performance. With the hybrid design, a conventional cone woofer provides low-frequency coverage.

And low distortion is what I was looking forward to hearing, along with the coherence of a single driver for the entire mid- and high-frequency range. In many ways, the hybrid electrostatic loudspeaker represents what might be an idealized approach for high-fidelity speaker design. My experiences with the EM-ESL and the bigger Montis have been both a delight and an education, and while they have at times been exasperatingly demanding in their placement requirements, the sonic qualities delivered have been among the best I have witnessed.


The MartinLogan Choice

No speaker review can be done in a way that is independent of the room within which it is evaluated. This seems to be truer than ever with dipole speakers. That sounds like a bit of a contradiction, the nature of dipoles supposedly freeing the user from a great deal of the room interaction complexities of monopole speakers with their wider radiation patterns. It is that rear wave from the dipole panel, containing every bit as much energy as the front wave, that can be either a curse or a blessing, depending on how much attention one pays to it in a given room. I ended up thinking of it as blessing then curse as time went on, and in later experiments found ways to constructively put it to use in crafting a monstrous soundstage.

In the end, this review covers three setup approaches for the EM-ESL speakers. In each case, the EM-ESL design both drives aspects of that approach and provides clear advantages in getting satisfactory results.
  • The straightforward on-axis setup approach which will suffice for many EM-ESL users.
  • The more exacting approach to achieve improved sound stage and imaging.
  • The "ultimate" setup approach, probably seen as entirely impractical by most, to achieve ultimate sound stage and imaging results.
When recently describing the critical nature of setup distances and angles and the experimentation time it can take to determine them in the third approach, a fellow enthusiast commented that it sounded like way too much trouble. I could only respond that the cost/benefit ratio made it all worthwhile: the soundstage and imaging potentially achieved were so enthralling and addictive that the trouble getting there became a small thing.

Other areas of performance where the EM-ESL speakers excel:
  • Low distortion from electrostatic panels, especially with the hybrid design where low frequencies which could drive the panel to fuzz-out and distort are handled by a cone speaker.
  • Quick response resulting from the low excursion of the large panel.
  • Wider dispersion with the MartinLogan curved panel, allowing off-axis listening angles which support a deeper soundstage.

Description

The EM-ESL is a hybrid electrostatic loudspeaker design with an XStat™ CLS™ (Curvilinear Line Source) curved electrostatic panel mounted on a sealed chamber enclosing a single cone woofer/low-mid driver. Quoting from the MartinLogan website:

"To seamlessly blend audio output from the high- and mid-frequency electrostatic panel to the low-frequency woofer the ElectroMotion ESL features a proprietary Vojtko™ topology filter utilizing custom air core coil and low DCR steel laminate inductors, polyester film capacitors in series, and low DF electrolytic capacitors in parallel.

A precise 8-inch high-excursion, perfectly balanced, audiophile grade, doped fiber cone woofer was custom designed exclusively for the EM-ESL by MartinLogan's in-house engineering team. This woofer precisely optimizes cone suspension and magnetic flux field to produce high levels of bass output and simultaneous precise midrange. The custom woofer's rigid light-weight diaphragm eliminates cone flexure and maximizes response time to achieve remarkably low distortion approaching that of MartinLogan's award-winning electrostatic panel design."

The panel is a dipole device, meaning that it radiates equally from its front and rear surfaces. Those radiating patterns are more tightly controlled than with normal monopole-type speaker designs. This means very little high-frequency sound radiates to the sides, giving the user more flexibility in speaker placement as a result of reduced interaction with room acoustics. It also gives the user the opportunity to make use of the rear wave in specific ways to generate the desired quality of soundstage and imaging.

The cabinet for the low-frequency driver in the ESL design is asymmetrical in two planes to reduce interior reflections and standing waves. Cabinet construction is sheet metal painted black, simple but not unattractive.

The crossover frequency is 500 Hz. That makes for a fairly broad range for the single cone driver to handle, and a fairly small driver at that. I was concerned about the range of frequency coverage required of that driver, as well as the fact that mid frequencies up to 500 Hz would be coming from a fairly low elevation, only about a foot off the floor. I spent quite a bit of time listening for anomalies in the crossover frequency range, for adverse effects on imaging, and for evidence that the low-frequency driver was being expected to do too much in general. There were no disappointments in performance in any of these areas, and in fact I was quite impressed with that driver's performance and with driver integration overall.

The EM-ESL tower stands on four feet which screw into the base, elevating it about 1 and 3/4 inches to allow the bottom-located port to operate properly. Each of these feet contains a threaded, screw-adjustable spike covered by a rubber pad. Once loosened slightly, the rubber foot can be turned easily by hand to level the tower or adjust its angle. With the pad removed - it can easily be pulled off by hand - a 3/8-inch wrench can be used to adjust the spike extension. I did not find the spikes to improve imaging over the pads, but they definitely helped stabilize the speakers to prevent creep from vibration or a minor bump.

The rear panel has a pair of terminals allowing either a bare wire connection, or, after removing a plastic insert from each, access to individual banana plug connections ("dual" bananas do not work, the spacing is wrong for them). There is also a blue indicator LED for power. It is necessary for each tower to receive DC power to bias its panel. A power supply with attached 10-foot cable is supplied for each speaker. An automatic sleep circuit deactivates speaker power after being silent awhile, and re-activate in about a second when an input signal arrives.

The 91 dB sensitivity level allows for quiet listening with a fairly small amplifier. But seasoned electrostatic panel users will advise the availability of plenty of power. The electrostatic design acts like a capacitor at high frequencies and the speaker impedance drops clear down to 1.6 Ohms at 20 kHz. The recommended amplifier power range is from 20 watts to 300 watts. How much is really enough? My own recommendations come later.




Specifications

Specifications

ElectroMotion ESL Loudspeaker
Frequency Response 42–22,000 Hz 3dB
Horizontal Dispersion 30
Vertical Dispersion 34" line source
High-Frequency Transducer XStat™ CLS™ electrostatic transducer
Panel Dimensions 34" x 8.6" (86cm x 22cm)
Radiating Area 292 in2 (1,884 cm2)
Low-Frequency Transducer 8" (20.3cm) high excursion, high-rigidity paper cone with extended throw drive assembly, non-resonance asymmetrical chamber format; bass reflex
Sensitivity 91 dB/2.83 volts/meter
Impedance 6 Ohms, 1.6 at 20kHz; Compatible with 4, 6, or 8 Ohm rated amplifiers
Recommended Amplifier Power 20-300 watts per channel
Crossover Frequency 500 Hz
Components Custom-wound audio transformer, air core coils, polypropylene capacitors Inputs
Power Draw Idle: < 4W/channel
Weight 35.5lbs. (16.1kg)
Dimensions 52.1 x 9 x 16.3
(132.3cm x 22.9cm x 41.4cm)


Associated Review Equipment
  • Music Server, foobar2000, Phenom II x6 1055T, 8 GB memory
  • M-Audio FireWire 410 Audio Interface (optical out)
  • Onkyo TX-SR705 Receiver
  • Crown Xs500 Power Amp
  • OSD Audio ATM-7 Digital 7-Zone Dual Source Speaker Selector with Remote Control

Unboxing

The EM-ESL arrived in two separate boxes which were shrink-wrapped together and strapped upright to a pallet in a semi trailer. The driver cut the strapping and the two of us carried the pair of cartons together from the truck into the house for further unboxing. At 36 pounds each, or roughly 80 pounds total for the packaged pair of speakers, it was not difficult for two people to transport the entire shrink-wrapped unit into the house in one trip.

The EM-ESL were easy to unbox and set up, completely assembled except for the feet to be screwed into the base. I appreciated that the large outer cartons easily folded flat, making long-term storage possible without taking up an entire room for packaging.





First Impressions

It really is almost difficult to make these speakers sound bad. The listener who chooses to set them up in the classic equilateral triangle will probably be delighted with the results and not bother to pursue anything further. That presentation is lively and clean, full of detail. Many will choose to spend a few hours finding optimum placement, and will be rewarded with soundstage and imaging every bit as good as any speaker I have heard in the price range and well beyond. The few sound chasers who go beyond that into what others would consider lunacy will be rewarded with sonics that are simply second to none in the price range, and may be difficult to achieve at all without making use of the MartinLogan hybrid design.

The EM-ESL spent time in 2 rooms of my house, neither with much in the way of acoustical treatment, yet both with surprisingly low RT60 times and with listener-friendly acoustical characteristics in general.

A few months ago I interrupted this review process to focus on the MartinLogan Montis (read the review here), one of the big brother hybrid electrostatic panel models. The Montis and the EM-ESL are very similar. The Montis is scaled larger and contains on-board DSP to drive its larger, powered mid-woofer driver.

The EM-ESL design is both finicky and versatile. This seems to be a reality with panel and dipole speakers in general. There are a lot of ways you can set them up and get great results, but each of those approaches has certain details to be paid close attention to.

The results can be nothing short of jaw-dropping. I expected good things from the EM-ESL, but had no idea they could deliver the quality of soundstage I was able to obtained from them. As is surely the case with other speakers and speaker designs, it is possible to get nice results fairly easily, and very good results without great difficulty. The question becomes how far you want to push, how much it is worth to get to the best performance possible. I will try to cover this entire range of possibilities in this review, from the quick-and-easy setup clear to the bordering-on-insanity level - the best soundstage possible. Some of the soundstage-chasing details will be written up separately, but enough will be included here to help the user decide if that is the route for them.

In a nutshell, I like the dipole principal a lot, more than I thought I would. These are simply great speakers. If one has a room that allows for it and the patience to go down the rabbit hole a ways in pursuit of the tip-top soundstage, they can deliver the kind of performance that I thought was only possible with speakers costing a lot more.


Vertical Sweet Spot Study

Early in the EM-ESL discovery process, a study was completed taking frequency response measurements every two inches up the height of the panel to find its area of most consistent frequency response, the vertical sweet spot for the panel.

The following paired curves were taken on-axis in-room at 0.5 m from the vertical plane of mid-woofer driver. The mic was moved straight up and down with the EM-ESL standing normal (normal panel tilt-back), so the mic-to panel distance varied slightly:
  • On-axis in-room response, with 1/6th-octave smoothing.
  • On-axis gated response, 5 ms IR window with 1/12th-octave smoothing.

Panel Height Frequency Response Consistency Study, every two inches - All Curves.

After a somewhat tedious process of sorting through groups of adjacent curves, it was seen that there is a sweet spot centered 31 in above the floor level.

Panel Height Frequency Response Consistency Study - Ideal Range Curves.

Panel Height Frequency Response Consistency Study - BELOW Ideal Range Curves.

Panel Height Frequency Response Consistency Study - ABOVE Ideal Range Curves.

Keeping the Listening Position (LP) located perpendicular to the center of this zone should provide the best image and soundstage stability with LP adjustments for comfort.


Soundstage Journey

The EM-ESL started out in our larger living room where I thought the best sonic results would be achieved. Existing furniture behind and around the EM-ESL would be randomizing the reflections of the rear waves which seemed like a good idea. In that environment, I listened mostly to music, some with the speakers aimed directly at the LP and some with them aimed with less toe-in to achieve a deeper soundstage.

I am never terribly excited by results of speakers set up in the equilateral triangle facing the listening position. The soundstage in that configuration was fairly wide with solid imaging but no soundstage depth to speak of. There are those who might favor this configuration for its simplicity, and will find little to be disappointed about in using it. I simply find that with a little extra effort the soundstage and imaging can be improved dramatically.

With less toe-in, the soundstage widens and opens, image clarity becomes much more specific and sharp, and the soundstage takes on a nice depth with the beginnings of a sense of depth acuity. Here is where the setup process starts to get more involved. In a room where the rear waves from the electrostatic panels do not travel along symmetrically-times background reflection paths, I found that any sharp reflections - those that would show up as sharp spikes on an impulse response measurement - were best dissipated or redirected to improve the image and soundstage clarity. As an example, at one point the rear reflection from the left speaker bounced directly off a small TV screen and back to the listener position. When I realized this and changed the angle of that TV screen slightly, the imaging and depth acuity improved markedly. Several such small discoveries in that room led to admirable soundstage and imaging quality, but never to the completely natural and totally sharp image clarity and depth acuity I had hoped for.

Upon moving the EM-ESL to my downstairs listening area, the results jumped to a whole new level of interesting.

Happy accidents in the realm of speaker setup are few and far between in my experience. The one that occurred upon setting up the EM-ESL in that room will never cease to amaze me. A bit pressed for time at the moment, they were placed quickly but with the measurements needed to ensure symmetry with the front wall and listening position. The soundstage and imaging that resulted were very wide and deep, with an open, natural air, a very clear sense of depth acuity, and a kind of density I had only witnessed one other time before that, from a pair of speakers costing 20 times the sale price. Upon adding a bit of equalization to tame the bass slightly and lift the high-frequency droop resulting from the off-axis listening angle, the soundstage density and depth acuity became even more impressive. I had to know why.

Most of the details of the investigation that ensued will be written up separately from this review. To summarize here, the diagram below shows the rear reflections from the electrostatic panels as they occurred from that initial setup. A totally blank wall, a pair of tower speakers sitting just outside of each EM-ESL, and a bookshelf were providing just the combination of rear reflections to give that soundstage and imaging result. The timing of the sharp reflections directly off the wall was such that they coincided precisely at the listening position, within a fraction of a millisecond. Had either of the review speakers been angled one degree differently - this was determined through later experimentation - the density and depth acuity would have been only fair-to-good instead of enthralling.

Example 1: Conditions initially producing dense soundstage.

Experiments to find other ways to achieve the same density of sound stage started with attaching reflective slats in different arrangements along the line between the rear-wave reflection points on that wide open back wall. Density of soundstage was achieved in this way, but with a sacrifice of the image precision and clarity.

Example 2: Vertical reflective slats on wall.

Better results were achieved by using smooth surfaces behind and beside the electrostatic panels, resulting in all reflections from the rear wall coming from very close to the same point. Excellent soundstage density was achieved with the image clarity I had first witnessed. Implementation was pretty impractical, however.

Example 3: Reflective panels beside EM-ESL speakers.

Then (i.e. a week later) it occurred to me that the reflective slat arrangement could be along the vertical lines above and below the rear wave reflection points and not disrupt the soundstage and imaging clarity.

Example 4: Horizontal reflective slats on wall.

At this point no doubt, even most avid listeners have declared insanity in the approach, or at least total impracticality. All I can say in my defense is, you gotta hear it to believe it. Admittedly, the quality of soundstage can be a higher priority to one listener than another. A similar quality of soundstage occurred at a Home Theater Shack speaker evaluation event in February. Two of the four listeners were enthralled by it, while the other two barely took notice, or were distracted by other listening qualities of higher priority to them. So I recognize that much of what I am describing will simply not matter to some listeners. My reason for going into this level of detail in this review is to let it be known what the EM-ESL are capable of. And that is a monstrously dense soundstage that almost seems carved in stone. There may be other ways to achieve it in other rooms; I am simply showing how it occurred in mine.

One must also note that similar results might be achievable with other speakers given appropriate attention to detail. The dipole's rear wave is perfect for the approach, though, with the MartinLogan hybrid design seeming the perfect implementation.


Equalization

There are those who will argue you should never have to EQ a speaker for it to sound right in your room. The high-frequency droop that resulted from the off-axis listening angle for deep soundstage was enough that some corrective boost was called for. I chose to accomplish that correction with a simple high-frequency shelf filter added to my foobar2000 music server. That, along with a little low-frequency correction, was all I changed, retaining the soul of the EM-ESL sound.

The needed correction was applied manually using the Reaper ReaEQ plugin in the George Yohng VST Wrapper with foobar2000 -- all free. The added high frequencies improved the imaging and depth acuity as well. The filter values were as follows:

Type Filter Frequency Amount Q BW
HF Boost HF Shelf 6 kHz +8 dB 1.0 1.4
LF Cut from 70 to 300 LF Shelf 1 300 Hz -3 dB 7.2 0.2
LF Cut from 70 to 300 LF Shelf 2 70 Hz +3 dB 7.2 0.2
Where: Frequency / BW = Q

Ultimate Soundstage Tuning

The EM-ESL "ultimate" soundstage and imaging have demanding setup requirements. How can one tell if it has truly been achieved? The best answer is achieved with impulse delay matching measurements, using Room EQ Wizard (REW) (or similar analysis program) and a measurement microphone. I got the clearest results with a regular (not USB) measurement mic using REW's timing loopback calibration method, so actual front and rear path delays could be measured directly and arrival times matched to a fraction of a millisecond.

But for a quick means of checking or fine-tuning, a short list of evaluation tracks was chosen, given below along with the particular sonic characteristics to listen for.

Actually, the final treatment method for thickening the soundstage - using horizontal reflection slats mounted along the vertical line below the reflection points on the wall in front of the listener - makes a dense soundstage somewhat easier to achieve. In other words, Example 4 above allows more placement flexibility than Example 3 above, thankfully. With the Example 3 setup, a speaker angle change of less than a degree could make a big difference in the soundstage - from "great" to "average." With the Example 4 setup, such a change would make a noticeable but much smaller difference.

Each EM-ESL speaker had a laser sight mounted on its woofer enclosure using double-sided mounting tape. A target drawn on a piece of white gaff tape on the room's front wall gave a reference point for checking speaker alignment and for evaluating the change to the soundstage and imaging with minor variations in alignment. The distance from the wall conveniently resulted in a one-inch movement of the laser dot roughly equating to a 1-degree rotation of that speaker.

All placement angles and distances came into play, however, including "pitch" and "roll," which strongly affected image clarity. Impulse diagrams show how the alignment of the reflected rear waves is almost perfect for the "ultimate" effect. That alignment of the reflected waves is what one is trying to achieve. It can be achieved by slight rotation of one speaker or the other or by small amounts of movement of the speaker in the appropriate direction.

The dissipation slats were in place for all of this exercise. An additional impulse diagram shows how their presence affects the reflected signal. The difference appears small, but the sonic result is dramatic.

A detailed alignment procedure will be given in another post.

Tracks and Expectations

Packt Like Sardines In A Crushd Tin Box - Radiohead (vol = -8):
0-deg (Reference Position) - Steel Drum: 3D location sharply defined beyond front wall. Kick Drum: A very dense, sharp pulse with impact, volleyball-sized image, sharply defined and focused. Vocals: Float in space, completely natural, 3D location sharply defined. Synths at 1:15, 1:53, 2:30: Dense, 3D location sharply defined, some well outside of and in front of speakers.

Chant - Fourplay (vol = -4):
0-deg (Reference Position) - Kick Drum: Very dense, small, tight, has impact, sharply defined and focused. Big Drum: Just right of Kick Drum, bigger, concentrated, surface well defined, the drum head jumps right out at you. Rain Sticks, Synths, Percussion: Float in space, thick & crisp, completely natural, 3D location sharply defined.

Two Knights And Maidens - Crash Test Dummies (vol = -6):
0-deg (Reference Position) - Acoustic Guitar Strums: Dense, precisely located well outside of and in front of speakers. Lead Vocal: Floats in space, completely natural, 3D location sharply defined. String synths at 1:30: Lower notes very dense.

Vision Of A Kiss - B-52's (vol = -6):
0-deg (Reference Position) - Acoustic Guitar Strum: Dense, has "body," floats in space, completely natural, 3D location sharply defined. Bass Guitar, Gourds, Tambourine, Vocals: Float in space, dense, natural feel, 3D location sharply defined. Guitar Strums, Guitar Chord, Organ at 4:30: Dense, float in space, 3D location sharply defined. When the organ dives into lower registers, the tone becomes very dense.

Ain't It A Shame - B-52's - (vol = -2):
0-deg (Reference Position) - Harmonica: All notes come from exact center. Centered Rhythmic Synth: Floats in space, strong presence, 3D location sharply defined. Lead Vocal: Floats in space, completely natural feel, 3D location sharply defined. The vocal echo high to the right clearly owns its own spot in the 3D space, very concentrated, with boundaries sharply defined.

Pyramid Song - Radiohead - (vol = -8):
0-deg (Reference Position) - Piano, Lead Vocal: Float in space, very natural, 3D location sharply defined. Cymbals at 2:00: Each hit is a sharp, single "ting," with no sense of doubling (two "tings" close together) from delayed reflections. 3D location is sharply defined with no ambiguity.

General
At its best, the soundstage completely separates from front wall and speakers, images are very relaxed and natural. Depth acuity becomes very precise. The ability to resolve the positions of images is very easy, wkth no location ambiguity.


Measurements

Measurement Graphs

Frequency Response:

The composite Frequency Response measurement method was completed out-of-doors. On-ground measurement of the lower part of the curve - measured at 0.5 m - is influenced by acoustical coupling between the bottom-mounted tuning port and the ground, or floor. Elevated measurement for the upper portion of the curve - measured at 1 m and 2 m - focuses on the electrostatic panel's response. The ground reflection with the elevated measurement method was damped by a thick pile of carefully-placed acoustical absorptive material.

Composite Frequency Response, combination of LF (on ground) and HF (elevated) curves, taken outdoors at 1 m and 2 m distances.

Composite Frequency Response, combination of LF (on ground) and HF (elevated) curves, taken outdoors at 2 m distance.

Reflection Control

Treatment of rear wave reflections for "simple" optimization of soundstage and imaging. In lieu of matching the left and right rear wave paths and reflection timings, dissipating or re-directing sharper reflections improved soundstage and imaging

Effect on impulse response of wave reflection off of chair back.

Effect on frequency response of wave reflection off of chair back.

Off-Axis Response and Equalization

Polar response in 15 degree increments (in-room gated IR response, 5 ms window) at 0.5 m.

Off-axis response at Listening Position (in-room, no IR gating), no EQ correction.

Correction filters used for equalization. See Equalization section above.

Off-axis response at Listening Position (in-room, no IR gating), with EQ correction.

Phase Response - Group Delay - Critical Soundstage Setup

Group Delay Comparison at Listening Position, with EQ correction. Phase response tracks very closely from 100 Hz up to 5 kHz, supporting sharp imaging and soundstage characteristics.

Impulse Response Alignment and Soundstage Thickening Reflections

Impulse Response, front and rear wave arrival times.

Impulse Response, front wave arrival alignment.

Impulse Response, rear wave arrival alignment.

Impulse Response, rear wave "thickening" by soundstage density reflections.

Distortion

I was very impressed that the mid-woofer driver's distortion was so low and that the crossover frequency of 500 Hz is barely noticeable in this curve. Evidence that the mid-woofer and electrostatic panel are a great match by design, expert integration in every way -- physically, acoustically, and electronically via the crossover.

Total Harmonic Distortion (low power level), measured on-axis at 0.5 m with no EQ applied. THD below the -40 dB line roughly equates to <1%, and below the -30 dB line roughly equates to <0.3%.

Step Response

These curves illustrate the impressively snappy response that electrostatics are known for, with minimal overshoot and fast settle times.

Step Response, speaker and mic on the ground outdoors, mic at 0.5 m. This measurement focuses on the mid-woofer driver's responsiveness with its port coupled to ground..

Step Response, speaker and mic are elevated and the ground reflection is damped with absorptive material, mic at 2 m. This measurement focuses on the electrostatic panel's responsiveness.






Loudspeaker or Listening Tool?

This section was copied from the Montis review located HERE.

As a listener, my idea of the possibilities for using a pair of speakers has changed a lot in recent years. The standard equilateral triangle with on-axis aiming was mildly satisfying for many years. Then began the period of experimenting with placement and angle to optimize Image Clarity and soundstage, essentially “getting the best out of a pair of speakers.”

With the MartinLogan EM-ESL, I found myself thinking less in terms of having speakers to optimize and more in terms of having a pair of sophisticated audio transducer tools to work with. The key characteristics of the electrostatic panel:
  • A single transducer that performs with:
    • Extremely low distortion, as the panel does not handle low frequencies and movements are very small.
    • Excellent frequency response.
    • Excellent phase linearity.
    • Effortless high-SPL capability.
    • Virtual-point-source precision.
  • Near-perfect matching between speaker pairs.
  • Perfect time alignment through the midrange and high frequencies because, well, there is only one transducer doing all the work.
  • Ultra fast responsiveness. There is almost no mass to be moved, so the panel starts instantly when called upon and stops just as quickly. With the EM-ESL, the concept applies to low frequencies, too. The ported woofer/low-mid speaker that covers up to the 500 Hz crossover point is critically damped, with minimal overshoot and settle times that complement those of the electrostatic panel nicely.
  • The high directionality, resulting in reduced room interaction, inherent in a dipole panel speaker. But not too high - the curved panel unique to MartinLogan’s design provides enough dispersion to allow off-axis listening angles where desired. That dipole directionality also gives the user a very good idea where sound from the panel will be traveling -- the rear wave from the panel contains the same amount of energy and the same directionality as the front wave. The strength of that rear wave means it must be dealt with carefully, which some may see as a downside, but its inherent directionality makes it easy to see the path it will be traveling and allows a little room treatment to go a long way.
In short, the EM-ESL represent a highly idealized approach to building loudspeakers, giving the listener a great deal of flexibility to achieve matchless sound quality in a variety of settings. They can be located close to walls, well into the room, even fairly close to the listener in a midfield configuration, they can be set in the classic equilateral triangle, or spaced wider, or spaced much wider, they can deliver great on-axis Image Clarity, or a deep soundstage with off-axis orientation, are great in a home theater setting, and terrific as two-channel speakers. I have a hard time imagining a tower application that could not be fulfilled with honors by the EM-ESL or a MartinLogan speaker in their bigger Reserve ESL line.





Two-Channel Evaluation

Frequency Response

For on-axis listening, the EM-ESL stock frequency response is wonderfully listenable, with smooth mids and highs, a minor 1.6 kHz presents peak that adds some liveliness without harshness, and adequately deep bass with just the right natural strength for my taste. With the rear of the base of the EM-ESL 3 feet out from the listening room's front wall, bass response was strong down to 40 Hz.

My preferred listening angle for good soundstage was about 30 degrees off-axis. There was enough high-frequency rolloff to call for some EQ to correct it for music listening. For home theater application, the 30 degree off-axis angle was the usable limit, with just-noticeable HF droop but more than adequate highs for the movies I auditioned.

For music, I applied EQ with manually-determined parametric filter values and alternately with Audyssey MultEQ XT, somewhat preferring the manual approach for its complete protection of the soundstage and imaging. Audyssey's correction would be adequate for all but the pickiest soundstage chasers.

Imaging and Soundstage

I lost track of the number of times I was thoroughly impressed by the work of that 8-inch mid-woofer driver and the way it has been integrated with the electrostatic panel. I had feared that having all sound up to 500 Hz coming from ankle level, a good 24 inches below the center of the electrostatic panel, might result in imaging issues. There were only a few occasions where image height varied slightly with tone, and it never drew attention to itself.

These speakers can easily be set up to produce "nice" imaging and soundstage - "nice" meaning adequate but not overly impressive, with solid imaging and a wide soundstage with some depth but little depth acuity - with a half-hour or so of adjusting and experimenting using a tape measure and a flashlight to set toe-in angle via reflection points on the panels. Get out the laser distance meter and spend another hour or two experimenting with placement, getting really particular about measurements and dedicating the space behind the panels, too, and the industrious listener can get to a soundstage and image clarity that stand apart - a "great" soundstage is achievable, with sharp imaging and good depth acuity in an open, natural soundstage.

Ultimate soundstage and imaging can be reached with luck - it happened to me - or, more likely, with Room EQ Wizard measurements and in-depth calculations and careful movements. The images seem carved in space, with clearly-defined edges. But it takes work, and only dedicated soundstage chasers will go in this direction.

The EM-ESL speakers are capable of it, though, as capable as any speakers I know, and the dipole design is perfect for this kind of soundstage crafting.

Dynamics and Headroom

In my medium-sized rooms, I pushed the EM-ESL speakers with the most dynamic passages I could come up with, and never felt them lacking in dynamic capability. At first, I did so with caution. After awhile, it became clear that any limitations were going to be at volume levels far above any I wanted to cauterize my ear nerves with. Searing rock passages, deep percussive booms, loud, sharp percussion, explosions, gunshots -- the EM-ESL were never impressed by my challenges. I was sure impressed by their handling of them, though.

Track Hopping

Nickel Creek - Ode to a Butterfly - Each of the instruments has body, presence in the room. The thickened soundstage effect makes string picking feel a little heavier than normal, but is not a distraction, and is partially a natural result of the spirited performance. Depth acuity is excellent. There are little instrument noise details that I have not noticed before. The standup bass is slightly less present than usual, though, because detail in the other instruments is accentuated.

Nickel Creek - Reasons Why - Sarah's voice is a very natural presence in the room, slightly inside the front wall. The vocal blend is perfect, each is precisely located. The standup bass holds its own on this track. I like the way the soundstage and imaging can keep delicate instrument sounds delicate and can give stronger strum and pick sounds solidity.

B52's - Ain't It A Shame - All of the harmonica notes come from the exact same spot, a sonic rarity. Cindy gets a presence boost that I like, but Fred falls back in the mix. The plunky centered synth stands out nicely.The echo of Cindy's vocals is a solid, tightly defined presence high to the right, a sure sign that the soundstage and imaging have been tuned properly. On this track, Cindy's sibilants occasionally seem to be overly thickened - further experimenting with the location and spacing of the dissipator bars is in order to find a remedy for this.

B52's - Good Stuff - The kick drum and walking bass line make you wonder if MartinLogan lied about the size of the mid-woofer driver.They are wonderfully detailed and punchy, solid with no sign of flabbiness.That 1.6 kHz presence peak might be a dB or so strong for this track - indeed, pulling it down 1 dB with a single parametric filter re-balances the upper mids and highs just right. I like very much the liveliness that peak provides, though. Only occasionally did it stand out a little strongly, and was clearly a result of my off-axis soundstage-tweaking listening position. The on-axis response with no EQ has that lively delivery with no over-brightness whatsoever.

B52's - Vision of a Kiss - The strummed acoustic guitar has such body on this track, you can almost make out its shape and size. The bass guitar has a unique character, with depth and pluckiness - the tight and natural feel of that sound alone says a lot for the quality of the mid-woofers and the integration of drivers and crossover in the EM-ESL speakers. I could not find a sound that tripped them up in the crossover frequency range, and I tried. Gourds and tambourine and vocals all occupy distinct places in the soundstage, all in a completely natural way - the psycho-acoustical brain is completely at peace with this soundstage, locations are so easily resolved, it says, "Yep, it is all real, no speakers in this room." The dual strummed electric guitars have a thickness that mesmerizes me every time I hear this track.

Cincinnati Pops - Introduction to 'Also Sprach Zarathustra;' Star Trek Theme - I am always a little fearful what the low thumps beginning the Star Trek Theme will do to smaller drivers, but I refuse to hold back the volume for their sake. The EM-ESL woofers punched out those beats with no hint of running out of steam and no mid distortion or loss of definition. I ran it again 2 dB hotter, then again another 1 dB hotter still, to where the orchestral passages following were almost too loud, and the mid-woofers were never strained that I could hear, never even gave that sense of compression that hints at limitation. No doubt some will insist the speakers would benefit from subwoofers, but I never felt bass-cheated without them in my listening tests.

The EM-ESL handled the orchestra with a fresh clarity and openness, even at high volume, that sounded easy.

Scott Davie - Variations on a theme of Corelli - I thought well-recorded piano would offer another opportunity to find driver integration issues, if they existed. Other than a slight tendency for notes in the lower register to stand slightly lower in the soundstage - as they do for most non-symmetrical speaker designs - there were no issues in evidence, and that tendency never drew attention to itself. The dynamic piano passages again allowed the EM-ESL to show off their quickness and clarity and ease of delivering detail.

I A-B switched between the Onkyo receiver and the Crown power amp on loudest passages. The Onkyo drove the electrostatic panels with no distortion or strain.

Melody Gardot - Baby I'm A Fool - Melody's voice can be difficult for a soundstage to resolve. She sounded perfectly natural on the EM-ESL.

Cassandra Wilson - Strange Fruit - Perfect. Every buzz, thump, and detail of the big standup bass, its depth and evenness, the clear, lonely, haunting trumpet, the quirky, stabbing Dobro guitar, and Cassandra's soulful, dynamic vocals - a perfect delivery.

Gorillaz - Rhinestone Eyes - Punchy synthesized percussion always seems instantly quick on the EM-ESL speakers, and super clean even when extremely dense. An occasional harshness on a track would have me turning the level down and repeating it to be sure the panels were not at fault.They never were. The soaring synths and dense vocals on this track approached over-brightness, but the "clean & smooth" factor kept them enjoyable. On-axis with EQ turned off, they were still quite bright. I blame the track.

Fourplay - Chant - This is a great instrumental demo track, with layers of sounds calling for good depth acuity to keep them separate, which the EM-ESL soundstage does effortlessly.

Nils Petter Molvaer - Khmer - Another layered track with lots of open space, this one with deep drums which the amazing soundstage keeps very focused and directional. As with most tracks, the speakers and wall completely disappear, the trumpet and other instruments hang in a sonic space far bigger than the room.

Porcupine Tree - Shallow - I have been asked recently if MartinLogan's speakers can ROCK. I cranked the volume on this track to ear protection levels, around 95 dB average (Onkyo & Crown amps), and the EM-ESL stayed clean-clean-clean-clean-clean, and nicely balanced. Yes, they can ROCK!

Radiohead's Kid A album in its entirety. With Radiohead, almost every song is a unique mix and set of instruments and sounds. Impressions: With the EM-ESL speakers set up for super soundstage and imaging, an album like this becomes a sonic trip of sorts, the width of the room and far beyond the front wall, filled with unusual instruments and sounds, all distinct, each occupying its portion of the time-space continuum with authority. Even my favorite track on this album, The National Anthem, which gets too busy for its own good in places, is resolved as well on the EM-ESL as on any speaker I have heard it on.

I have been listening to/these speakers for, er, ahem, longer than I should admit while completing this review. While there have been countless variations of placement and soundstage-enhancement treatment, the core of their sound has remained constant for me: clean, balanced, natural, easy to sink into and enjoy. As mentioned earlier, their ability to produce imaging with no ambiguity of spatial location allows the psycho-acoustical brain seemingly to let go of certain processes and relax one into the musical experience at hand.

Beethoven - F. Reiner - Chicago Symphony Orchestra - Symphony No. 7 In A Op. 92, all 4 movements - When given orchestral tracks to deal with, the EM-ESL can be a bit too revealing at times. Recognizing that recording an orchestra well is one of the great challenges a recording engineer can face, most of my orchestra listening time ends up being an experience of discovering recording and mixing flaws. Good speakers can do that to you.

Still, there are parts of this recording I enjoy very much, and the EM-ESL speakers are made for good orchestra tracks - clean-clean-clean, and so balanced, handling orchestral dynamics effortlessly.

Michael Hedges - Layover, The Happy Couple, Eleven Small Roaches, The Funky Avocado - These acoustical guitar tracks, chosen that they might reveal some imperfection in driver/crossover integration, came the closest to accomplishing it. Lower string tones, some sounding down-tuned, clearly came from lower in the soundstage, sometimes sounding like a separate instrument "down there." Only once was there a part of a string tone that smeared low with an artificial feel. Other than that one moment out of many focused attempts to foil the engineering that went into these speakers, there were no occasions where the effect was distracting or would even be noticed by most discerning ears. I was left thoroughly impressed by the performance of that 8-inch mid-woofer and the way it performed with crossover and electrostatic panel. I would love to see a symmetrical MTM, or rather woofer-panel-woofer electrostatic configuration some day, but that is another discussion altogether.


Cinema Evaluation

The Fifth Element: The soundtrack through the early scenes of this movie contains a steady series of deep rumbles and low-frequency sounds, along with other miscellaneous effects. My favorite movie sound effect occurs early in the film as Ultimate Evil expands, a multi-part tearing, searing sound which, at volume, fills the room just as the effect fills the scene. I was again impressed by the way the mid-woofer pumped out the low frequencies while keeping pace with the lower-mid-frequency content of the soundtrack. A rattle during one scene turned out to be an item in the room that picked up a vibration, not a problem with either of the EM-ESL speakers themselves.

The battle scenes at Fhloston Paradise are less bass and more mids and highs, placing more stress on the panel than the mid-woofer. With volume levels rivaling those in a large movie theater, or very loud, the EM-ESL cranked out gunshots, explosions, crashes, and impacts, all with complete freedom from strain or limitation.

Collateral: The Club Fever scene contains a number of bone crunches and gunshots, punctuated by the tinkle of breaking glass. All was handled easily by the EM-ESL. Volume levels were run very high.

On-axis, the tonality was almost completely transparent. Dialogue was well presented by that 1.6 kHz presence peak, although not as strongly as with speakers voiced more specifically for cinema use. I actually thought dialogue stood out more clearly at a 15- to 30-degree off-axis seating angle, with the slight resulting loss above 3 kHz.

Phantom imaging, of course, was excellent.

All in all, the EM-ESL speakers handled cinema soundtrack material extremely well, with perfect clarity and great dynamics. If anything, the transparency drew attention to mixing issues.


Overall Listening Experience

Delightful. Listening through the EM-ESL speakers is an easy, natural, revealing experience.


Conclusions

The MartinLogan ElectroMotion ESL Hybrid Electrostatic Loudspeaker, at $2,195 per pair MSRP, is a speaker I can highly recommend. While the dipole design does help free the listener from some of the effects of room acoustics, it also demands that the rear-wave path be paid attention to. The result can mean less room interaction for simple setup approaches, but will mean much more work and attention to detail for the discerning (super-picky) listener who wishes to achieve the best possible imaging and soundstage. The rewards are more than worth the trouble in my opinion.

A versatile speaker, the EM-ESL runs clean-clean-clean, handles dynamic material with ease, and can basically deliver any kind of music with transparency even at generous volume levels. Driver/crossover integration is excellent and frequency response is lively and accurate. The single 8-inch mid-woofer driver could possibly hold back the truly bass-hungry listener and a big room with high-volume requirements might lead one to consider a large-panel MartinLogan hybrid model, but neither of these areas was ever a problem for me.

I will not say that the MartinLogan hybrid electrostatic speakers are meant for everyone. I will readily say that they are a great choice for those who love clean, dynamic music and home theater delivery and are willing to be "responsible" dipole speaker owners.


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