Secrets of Home Theater and High Fidelity - Best of Awards 2017
The MartinLogan EM-ESL X speakers represent MartinLogan’s latest attempt to squeeze the most performance into an affordable platform that they are capable to pull off.

These speakers impressed with a lifelike sound that improved on the dynamics and soundstaging of past efforts. The included passive woofer blended nicely wit the upper ranges while offering low-distortion output to the mid 30 Hz range.

Front and Back view


MartinLogan ElectroMotion ESL X Floorstanding Speaker

  • Electrostatic speakers with large high-end panels
  • Dual 8” woofers in each channel
  • Balanced sound
  • Surprising dynamics and treble extension
  • Excellent bass response within design limits

I have always loved electrostatic speakers ever since I first heard a pair at a high end shop in San Francisco many years ago. These ElectroMotion ESL X speakers from MartinLogan caught my eye at the 2016 CEDIA Expo. I was not able to listen to them at the show but the description of the various advancement as well as the specifics of the design were more than enough to pique my interest.


Electrostatic Main Driver with Dual Passive Woofers


41 Hz – 22 kHz, +/- 3dB

High Frequency Transducer:

XStat™ CLS™ Electrostaic Transducer (40” x 8.6”)


2 ~ 8" Drivers


Bass Reflex (Ported)

Crossover Frequency:

400 Hz

Sensitivity (2.83V @ 1 m):

91 dB

Nominal Impedance:

6 Ohm (Min. 1.6 Ohm at 20 kHz)

Recommended Amplifier Power:

20 – 400 watts


52 lbs. each

Dimensions (HxWxD):

59.2” x 9.4” x 20.7”

Available Finishes:

Black Satin (High Gloss Black Available for an Upcharge)

MSRP ElectroMotion ESL X Floorstanding Speakers (Pair):

$3,999.95 USD




MartinLogan. ElectroMotion, ESL, Electrostatic, Floorstading, tower, hybrid, ESL X, Floorstanding Speakers, Main Speakers, Full Range Speaker, XStat™ CLS™ electrostaic transducer, Speaker Reviews 2017

Well it didn’t take very long for me to make a formal request for a review pair of ElectroMotion ESL X. I think it is well worth it for you to take a few minutes and read my entire review of these speakers because they may be just what you are looking for.


I was first introduced to the MartinLogan ElectroMotion EM-ESL X speakers at the 2016 CEDIA Expo. The marketing people from MartinLogan described the design concept of these speakers something like this, “We set out to make an electrostatic speaker with the highest possible performance at the lowest possible price point.” Being a very pragmatic engineer myself, that one sentence brought about my most immediate and intense interest in these speakers.

I have never been a sucker for overtly flashy products. I am interested in pure performance first and foremost. Any unnecessary frills or filigree are of little interest to me. I want my audio products to sound good. Period. Extra stuff that doesn’t promote improved sound just adds to the cost and complexity of something that should be purpose-built.

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But of course there are minimum standards of decorum that must be accommodated. You wouldn’t want a speaker cabinet of unfinished plywood, for example. The beauty of an electrostatic floor standing speaker is that they are gonna look cool no matter what. The main drivers are see-through and the advancements over time have brought them very close to visual transparency. (The panels on the EM-ESL X’s, for example, impart only the slightest darkening of light that passes through.) So the look of the speaker is largely defined by this unique and enduringly cool flat panel driver. What’s left is the woofer cabinet at the base. For the EM-ESL X’s, it’s finished in satin black paint; all the better than some delicate veneer (IMHO).

In a domestic-setting

My point is that others in my family can be picky about the look of the floor standing speakers I review. Amazingly, I didn’t hear a single negative comment about the EM-ESL X’s (particularly while the music was playing!)

Let’s dig into the design a little deeper. The electrostatic panels of the EM-ESL X’s are reasonably large at 8.6” wide by 40” tall. The narrow width promotes better horizontal dispersion while the increased height offers a number of advantages, the most important in my view is the promise of higher SPL’s and improved dynamics.

The real advance that MartinLogan builds into these panels to improve sound staging is the CLS design concept. CLS stands for “Curvilinear Line Source”. This is the concept that the panel is curved so as to promote wider horizontal dispersion of the sound waves. It is the product of significant R&D investments and helps overcome one of the biggest deficiencies among early electrostatic speakers – their propensity to beam the sound which back then meant poor imaging and difficult speaker placement.

The EM-ESL X’s include the most up to date version of MartinLogan’s electrostatic panel. This has been dubbed the X-Stat Transducer. This refers to the design of the stator panels. This new design nearly doubles the open radiating area of the transparent panels. This sounds like it would be easy to implement by having more or larger holes in the stators, but there are two problems that must be overcome – the stators must engage the whole panel and they must be rigid enough so as to limit deflection even under high excursions. This is where MartinLogan’s Air Frame technology comes into play – the panels are locked in place by way of a very rigid outer frame work.

Top View

One additional and inherent advantage of the EM-ESL X’s design is that they operate natively as dipoles which makes speaker placement a little more important but really improves the ambiance of the audible performance once dialed in.

Of course, electrostatic panels don’t reproduce bass with enough extension and authority for most modern systems and listeners. That’s why all of MartinLogan’s electrostatic speakers are a hybrid design with conventional woofers. In the case of the EM-ESL X’s, each bass module combines two 8” high excursion doped fiber woofers in a ported enclosure. The asymmetrical chamber reduces cabinet resonances.

Both woofers are active but not powered. It goes without saying that deleting the on-board amplification was one measure by MartinLogan that kept the cost down. I do not see this as a “problem” because the EM-ESL X’s are rated at 91 dB efficiency which means they can be driven by amplifiers as low as 20 watts per channel. The biggest downside is that these speakers do not have a Perfect Bass Kit due to the absence of an on-board amp.

Rear and Bottom Views

These woofers cross over to the electrostatic panels at 400 Hz. The passive crossover network in the EM-ESL X’s is a Vojtko™ topology filter utilizing custom air core coils and low DCR steel laminate inductors, polyester film capacitors in series and low DF electrolytic capacitors in parallel. This acoustic crossover has 24 dB per octave high and low pass filters. The advantages of this filter technology are that it offers a very precise crossover with minimal interference to the signal.

These speakers are bi-wireable and bi-ampable by way of two pairs of binding posts per cabinet. These are MartinLogan’s famous binding posts that can be used with banana plugs, spades or bare wire. The shape of the posts promotes easy tightening when using spades or bare wire.

Spiked Feet with Rubber Boots

The EM-ESL X’s also have some of my favorite feet. They lock into place and can be used on bare floors or carpeted surfaces. (They have rubber “boots” that slide over the spikes during set up or when on a bare floor. These can be easily removed by sliding them off to expose the spike underneath.) I liked this more than the format where you have to interchange the spikes for different floors. Plus, a lot of spike systems don’t lock down as well as the ones in the EM-ESL X’s.

One other advantage of the electrostatic design – the panels are light weight compared to a typical speaker cabinet. So they were much easier to move around the room than typical tower speakers with dynamic drivers. Their net weight is only 52 pounds each!


Setting up speakers is a breeze for me. That’s because I test speakers in the same room over and over again. I found the best speaker locations years ago. These spots are marked on the floor with masking tape.

However, the EM-ESL X’s are dipolar which means that I did play around with their spacing from the front wall. In this particular situation, I moved them closer to the sitting position than usual so that the panels were approximately 3’ from the front wall. This provided the best integration of bass for my particular set up.

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The side-to-side spacing of the speakers was roughly 10’ while my chair was 9’ from the plane of the speakers. This meant that the triangle formed was more obtuse than the typical equilateral triangle I strive for. I would normally fear a hole in the middle with such an arrangement, but the EM-ESL X’s have way better imaging than any electrostats I have reviewed before so there were no issues with staging and center fill.

I do want to point out that MartinLogan ships one of the most thoughtful and technically useful owners’ manual that I have ever read. This manual has a long and detailed section on set up principles that is very much worth a thorough read through.

Basic Zobel Network

This manual suggests a flashlight test where you sit in the prime seat and shine a light on the panel. This creates a reflected light bounce that is used as a guide to ensure proper (and equal) toe-in of the speakers. I did this drill.

I also connected a pair of Zobel networks in parallel across the terminals as per this “Little Things” post by John Johnson Little Things: Using a Zobel Network to Reduce Harshness with Electrostatic Speakers. These networks really do create a smoother, more natural sound.

Once I had everything sounding the way I wanted, I removed the rubber bumpers from the feet to expose the spikes. We have carpeted floors with a very thick pad that some spikes cannot fully penetrate. The EM-ESL X’s spikes suffered no problems and seated firmly to the sub floor.

In Use

These speakers have me reflecting back to a time many years ago when I heard a pair of MartinLogans for the first time. I was in a high end shop in San Francisco in the early 90’s. I do not know what model of speakers they were exactly. What I do remember is that the CD player, the pre amp and the power amp were all Krell. And I also remember what really stood out was the transparency and naturalness of the sound that differentiated those speakers from speakers that used dynamic drivers. This was an impressive performance.

Fast forward a few years to the 2016 Winter CES and I had the opportunity to audition a pair of ML Neoliths being driven by Constellation amplification. That right there was the best I have ever heard from a pair of electrostatic speakers of any brand.

Now enter the EM-ESL X’s and I can confidently state that, though not up to the quality standards of the Neoliths, the EM-ESL X’s were nevertheless the best sounding electrostatic speakers that I have ever had in my personal system. Back in the day, electrostats tended to be more midrange forward and less dynamic than conventional speakers. Well that just isn’t the case any more. The EM-ESL X’s conveyed an intoxicating, delicate treble that was well in balance with the midrange. They were also dynamically unrestrained for the most part.

Probably the most negative comment I have is that, these speakers tended a little toward the analytical side but they definitely did not lack heart. They just sometimes etched the sound a little bit.

Doyle Bramhall's Rich Man

Doyle Bramhall Rich Man

Another important observation was how seamlessly the bass integrated with the midrange. A great test of this integration was Doyle Bramhall II’s recent release on vinyl, “Rich Man”. This guitar maestro’s album features a “rich” and powerful sound. (See what I did there?) The EM-ESL X’s showcased this quality brilliantly.

I especially enjoyed the strong output in the 100 – 500 Hz region. Strong and clean that is. I mention this because some hybrid speakers can have a lean presentation in the power band but not the EM-ESL X’s. These bad boys were fleshed out for dang sure.

These speakers have rated bass extension to 41 Hz which is borne out in the bench tests below. I heard it too. I still preferred these speakers crossed over at 60 Hz to my SVS SB 13 Ultra sub. This sub has a tight, clean and deep response. Though some may venture that the lowest bass is not really audible and vinyl has limited bass extension, I do not agree. There was something special about the sound with a real sub picking up the duties below a reasonable crossover. 80 Hz was too high, 40 Hz was too low and 60 Hz was just right. I did most of my listening with a sub.



What about the question of a dynamic sound you ask? “La La Land” is my simple reply. I still haven’t seen this movie yet (oops). I did get the soundtrack on vinyl and I can say that this is quickly becoming one of my favorite albums.

It covers the gamut of a wide range of musical styles. More than any other part, though, the big band sections just blew me away over the EM-ESL X’s.

You know you have a great sounding audio system when it can pass the sound of a bank of horns playing full tilt in a way that doesn’t diminish the visceral qualities of the real sound of horns in the wild. Be forewarned though that this soundtrack is a hard-to-shake ear worm.

I used these speakers in a cinema application too. They were paired with a Paradigm Prestige 55C center speaker. My surrounds are in-wall/in-ceiling speakers from GoldenEar. The sub was the aforementioned SVS SB 13 Ultra crossed over at 60 Hz. I used an AudioControl Maestro M9 SSP with Dirac Live during this review. Amplification was by way of an ATI AT2007 amplifier.

Even with high end room correction, I was never able to get the best blend possible between the MartinLogans and the Paradigm center. The surrounds were less of a concern more by virtue of how soundtracks are mixed and not by the relative technologies of the speakers. I mention this because if I were to use the EM-ESL X’s in a full time surround set up, I would opt for a matching center speaker for the best possible results.



One Blu-ray that blew my mind in this system was X-Men Apocalypse. This is an amazing action adventure/sci-fi movie. The soundtrack is beyond reproach as well. Here again, the MartinLogans handled all the bombast without complaint. These speakers tested out with low distortion at high SPL’s and the big payoff is with movies like this.

All the effects were rendered with an ease and a tonal balance that kept me engaged in the movie throughout.



I also reviewed the Blu-ray of Prince’s greatest movie, “Purple Rain” while I had these speakers in play. This was the best of both worlds – a movie with great music. Once again, the sound was the highlight of the presentation and I enjoyed an at times raucous and at other times delicate sound that was worthy of a second viewing (yes, I did!)

On the Bench

All below measurements are in-room response. The frequency response tests were performed with the microphone on axis with the electrostatic panel and spaced 2 meters from the panel. The distortion measurements were on-axis near field measurements with the microphone tip precisely 1’ from the driver under test.


This first test is one that I do as a baseline for the level of distortion a speaker produces. The EM-ESL X’s made a strong showing by producing only 0.44% THD+N at 1 kHz and 90 dB. This is a very good result and emboldened me to run some tests at higher output levels.


Moving up the spectrum, I obtained the above results at 5 kHz and 100 dB. This is very loud even in a nearfield setting. The MartinLogans mustered this output at just 0.46% THD+N.


Also at 100 dB, this test at 10 kHz was a real eye opener. THD+N was measured just 0.37%. Most speakers struggle with this test, but not the EM-ESL X’s. I think it is because the extremely lightweight panel has so much radiating area that it can crank higher SPL’s than conventional tweeters.


Moving down the spectrum from 1 kHz, the above plot gives the THD+N readout for a 500 Hz sine wave played back at 100 dB clocks in at 0.80%.


This plot is again 100dB but at 250 Hz. THD+N = 0.55%


In testing the bass region, I was impressed with this low distortion reading at 80 Hz. The THD+N at 100 dB measured 1.33%. This is considered inaudible at this frequency.


The EM-ESLX’s performed well in the low bass too. Here is a plot at 40 Hz and 100 dB that registered 4.16% THD+N. Most experts agree that 10% THD+N is the threshold of perceptibility in the low bass. Not shown is a test I ran at 40 Hz that reached about 9.3% THD+N at 106 dB.

Pink Noise

The above plot is the on-axis frequency response using pink noise. I used pink noise as it is less of a strain on the amplifier (and speakers) though it gives a cascading plot. Besides the typical room interactions in the bass, what you can see is that the EM-ESL X’s have bass extension to the low 30 Hz range and response above 400 Hz that is super S-M-O-O-T-H!


THE MARTINLOGAN ELECTROMOTION ESL X SPEAKERS are the best-sounding electrostatic speakers I have ever auditioned in my home.

  • High cool factor
  • Improved dynamics and staging
  • Very musical
  • Excellent build quality
  • Relatively lightweight
Would Like To See
  • Built-in, defeatable Zobel network

I think MartinLogan really hit their mark with these speakers. Like most electrostatic speakers, they have great clarity of sound with a vivid mid range. Add that the EM-ESL X’s improve on the dynamic presentation. This, along with enhanced dispersion and staging qualities means you have a very worthy product for just about any system that needs floor standing speakers.

I also think they have an incredible coolness factor. Every non-audiophile who comes over is immediately stuck by the unique visual appeal of the transparent panels. People ask if they actually make the sound (as if they are decorative in some way, chuckle). I tell them of course they do and then start up some music. Then they are taken aback by the immediacy of the sonic presentation.

I don’t think electrostatic speakers are for everybody. Try them out and see for yourself. They ain’t cheap but they are worth every penny as far as I am concerned.