When it comes to speaker systems capable of delivering music with almost magical realism, MartinLogan is one of the first names that comes to mind. Their electrostatic speakers have long been legendary among music lovers. Today, we will take a closer look at one such model — the ESL X, which strikes a successful balance between cutting-edge technology and relative affordability.
The main feature of these speakers is their huge, almost transparent electrostatic panels. Unlike conventional speakers with diffusers, they create sound that is evenly radiated into the space. This can be compared to a live performance: the music does not “hit” from a single point, but gently surrounds the listener, filling the room.
Expectations for the ESL X are usually very high: detail, airiness, and clarity. But the main question is whether they are capable of not just impressing on demo recordings, but becoming an unobtrusive and musical companion for everyday listening. This test is about how well they cope with what is perhaps the most difficult task.
Their methods
An electrostatic radiator in its purest form is a very thin membrane located between two metal grids called stators. When a high-voltage signal modulated by an audio signal is applied, an alternating electrostatic field is created between the grid and the membrane, causing the membrane to move.
As practice shows, it does this much more accurately than dynamic emitters, providing a more linear frequency response and a distortion level that is one or two orders of magnitude lower. Without going into details, electrostatic emitters seem to be the ideal solution for Hi-Fi.
But if you try to apply them to audiophile needs in practice, a number of technical problems will arise — the very ones that have scared most manufacturers away from electrostatic speakers.
The first problem is low frequency reproduction. The lower the frequency, the greater the working stroke of the diffuser must be. And while a conventional speaker can easily be made long-throw, ensuring a diffuser amplitude of a good centimeter or even more, the membrane of electrostatic speakers has a working amplitude that is many times smaller. It is possible to compensate for the lack of long excursion by increasing the area, but in this case, even for reproducing upper and middle bass, a monstrously large radiator would be required.
To be fair, it should be noted that electrostatic bass radiators do exist—they are used in one of MartinLogan's top models, but this is the very same fantastic high-end technology that balances on the edge of what is real and reasonable. In all other cases, the company's engineers use a much more reasonable and practical solution—hybrid technology.
In this technology, the mid and high frequencies are reproduced by an electrostatic driver of reasonable size, while the low frequencies down to the lower midrange are reproduced by one or more dynamic drivers.
The second problem is radiation directionality. The flat membrane of an electrostatic radiator provides directional radiation. This is not noticeable at all and does not play any role when it comes to headphones, but it is very noticeable when listening to a speaker system, which will have to be directed at the listener even more precisely and strictly than when using speakers equipped with a horn or conventional dome tweeter.
MartinLogan engineers also solved this problem by creating CLS (Curvilinear Line Source) technology — an electrostatic driver whose surface is curved like a section of a vertically mounted cylinder.
Thus, while maintaining vertical linearity, the CLS driver provides uniform output across the height and does not require the user to manipulate the height of the seating position, while the curvature of the membrane disperses sound at 30° in the horizontal plane, providing a comfortable listening area that is wide enough to accommodate more than one person.
These methods have freed MartinLogan electrostatic acoustics from the main problems of the technology, and now we can move on to the details, which are best illustrated with a specific example.
The MartinLogan ESL X is a speaker that sounds so subtle and natural that you stop noticing it, but you catch every detail of the music. They don't overwhelm, shout, or boast about their power, but simply reveal the recording — honestly, with air and space. If you want to hear not just sound, but live music in your room, these speakers will meet your expectations without requiring a perfect room or a fancy amplifier.
Active or passive?
The most difficult and confusing aspect of classifying MartinLogan speakers is determining whether they are passive or active. Electrostatic technology itself involves supplying voltage to the stator, which comes not from the amplifier but from a separate power supply, which in a way makes these speakers similar to traditional active speakers. However, the fact that they are externally powered does not eliminate the need for a sufficiently powerful amplifier, which means that they are not active electrostatic speakers after all.
It gets even more complicated. As mentioned earlier, virtually all MartinLogan electrostatic speakers are hybrids because they contain an additional low-frequency section with traditional drivers. The company's model range includes two series of such speakers: in the higher-end Masterpiece series, the low-frequency section is active, while in the lower-end ElectroMotion series, it is passive.
Thus, in all cases, the midrange/high-frequency section remains passive (but with an external power supply that creates an electrostatic charge), while the low-frequency section can be either active or passive. The ESL X model we tested belongs to the ElectroMotion series, which means it is a completely passive speaker.
Checking the package contents
So, gradually sorting through the details, we finally got to the star of the show. The ESL X model, the flagship of the ElectroMotion series, differs from its younger siblings in its larger electrostatic panel and the wider frequency range it reproduces.
In absolute terms, we are talking about an electrostatic module measuring 1,020 x 220 mm, or almost a quarter of a square meter in area, which operates from 400 Hz. A distinctive feature of the proprietary emitters is the use of an ultra-thin Mylar film and a lightweight metal stator grille design.
The curved profile of the radiator plays a positive role in increasing the rigidity of the structure, so there will be no problems with reliability and unwanted vibrations. As a result, the speakers look light and elegant, and the electrostatic radiator section looks transparent from a certain angle.
The 41–400 Hz range is reproduced by a pair of 203 mm long-throw speakers with reinforced paper cones. When viewed strictly in profile, it can be seen that the four walls of the low-frequency section are not parallel.
This geometry eliminates the possibility of standing waves forming, and the axes of the speakers' radiation are directed not only in opposite directions, but also at different angles to the horizon. At the bottom of the low-frequency section is a large-diameter phase inverter port. It works thanks to high-resistance spikes. If necessary, the spikes can be converted into feet using rubber protective caps.
The drivers are matched using a crossover manufactured using the Vojtko method and named after one of MartinLogan's developers. The essence of the method is to consider all the electrical characteristics of the drivers as an integral part of the frequency filter.
Next come the traditional methods — the use of high-quality filter components and final tuning by ear in a room similar to a typical living room. Two pairs of terminals are used to connect the speakers to the amplifier, which is more justified than ever in this situation.
In two directions
Before discussing the sound in detail, it makes sense to pay attention to another feature of the electrostatic radiator — the nature of the radiation. Since the stator grids between which the membrane is located have the same perforation, it is, in fact, a dipole radiator that creates sound waves of equal intensity in front of and behind itself.
At the same time, it has no enclosure, which means that an acoustic short circuit occurs at the edges of the emitter when the radiation from the forward movement of the membrane encounters radiation of similar strength but opposite phase, arising from the backward movement of the membrane.
Thus, the speaker radiates forward and backward, but has minimal radiation to the sides and upward, which in turn minimizes unwanted early reflections from the walls and ceiling. And the reflection of sound coming from the rear of the speaker offers the same advantages as any other classic dipole design — it makes the soundstage more spacious and deeper.
The ESL X model is capable of creating a spacious soundstage with uniform sound coverage in virtually any location. Typically, with the exception of small areas to the side of the speaker, the sound is equally loud, clear, and intelligible throughout the rest of the space.
But it would be a big mistake to think that filling a room with sound is all that electrostatic speakers are capable of and designed for. By spending enough time finding the optimal placement for the speakers, you can achieve a holographic, fantastically accurate stereo image with tangible three-dimensional sound images that have realistic dimensions and proportions.
However, conveying the skill of proper speaker placement is quite difficult. Given the dipole nature of the radiation, the room actively participates in the formation of the sound image—especially the wall behind the speakers, which essentially makes each installation unique.
From general observations, it can be noted that, despite the curvature of the front panel, the speakers still retain a noticeable directionality — and the area in which the sound will be perfectly focused can accommodate a maximum of two people. Slightly to the side of it, there is already a noticeable drop in high frequencies, and the soundstage does not seem perfectly clear and holographically accurate.
The second observation, applicable in various conditions, is the distance from the back of the speaker to the wall behind it. The optimal location is linked to two factors: the size of the room and the distance from the speakers to the listening point. For this reason, it makes sense to start the search for the optimal location from the reverse process: finding the focus points for different installation options.
The statistics collected in this way will help you find the optimal position of the speakers relative to the desired listening position. But be prepared for the fact that your expectations may not match the possibilities 100% — and the best focus point may not be where you would like it to be.
And one last piece of advice from Captain Obvious: the ESL X speakers require a fairly large listening room. At 1.5 meters tall, they will look strange in a 10-15 square meter room, and it will be difficult to get good sound out of them.
At the same time, this model is not afraid of large rooms — not at all. The feeling of excessive sound pressure appears much earlier than you can turn the volume knob to the maximum, and there is no hint of distortion.
More than usual
Sound quality is the criterion we most often associate with cost. “Do the speakers deliver value for money or not?” — that is the question! And let's be honest: not every high-end speaker system lives up to expectations, even though it has every right to do so — after all, we are talking about maximum quality for any price.
But in the case of the MartinLogan ESL X, which costs about as much as an inexpensive car, this issue doesn't even come up. The degree of transparency and detail in the sound is so high that any price tag will seem normal, provided that the source and amplifier allow you to hear it. This is a very important point when evaluating the sound of electrostatic speakers, since the actual level of distortion introduced by the speakers may be lower than that of the components — and it is their shortcomings that will be audible.
It is also important that the exceptional detail is combined with smooth phase and frequency characteristics, rather than accents in certain areas of the frequency response, as is the case with some studio monitors and home speakers. Even the combination of an electrostatic dipole with a dynamic dipole, which also operates in the lower midrange, had absolutely no effect on quality.
The crossover is not noticeable — the low-frequency section is indistinguishable in terms of sound character and is not defined in space as a separate sound source. This is partly due to the fairly large listening distance, but the main contribution comes from the well-thought-out mutual arrangement of the drivers in space and relative to each other — and, of course, the proprietary crossover.
The speakers are also notable for their excellent microdynamics and sound integrity. Most interestingly, while demanding high quality from the electronics, the speakers are surprisingly forgiving when it comes to content quality. Simpler mastering and low-bitrate streaming audio can be listened to without causing discomfort or organic rejection, as is often the case with systems that have high detail.
If you approach the sound with the utmost rigor and exactingness, you can also find weaknesses in the MartinLogan ESL X. For example, metallic sounds are softened, even when listening at the focal point. This can be noticed in comparison with the sound of ribbon and, say, aluminum dome tweeters. As a result, the ringing of metal and the sound of brass instruments are somewhat softened and not as natural as, for example, the sound of vocals or woodwind instruments.
Another feature: bright and sharp sounds — for example, snare drum hits — are sometimes reproduced very delicately. Sometimes it even seems that the developers deliberately arranged everything in such a way that the acoustics would not cause discomfort to the listener.
For listening to chamber classical music, baroque music, or calm jazz in the spirit of Norah Jones, the character of the acoustics is perfect. I listened to the familiar “Come Away With Me” in detail—the sound is so fluid and enveloping that it is literally tangible. Similar sensations are evoked by electronic music of a similar character—for example, Dido or Moby.
The music of the eighties made a particular impression. All those gated drums and analog electronic sounds are reproduced very organically. Even the sound of rock music recorded in those years is perceived as absolutely whole. Needless to say, albums like “Brothers in Arms” and “In The Air Tonight” can be listened to endlessly — and each time they touch the soul deeply.
Modern recordings of various genres impress with other qualities: superb detail, a boundless sense of space, or, conversely, deliberately low-quality mastering, which, when performed by the MartinLogan ESL X, feels exclusively like a beautiful artistic technique — something whole and complete. And regardless of the style of mastering, every talented and sincere performance touches the soul no less than records that have been tested over decades.
This model successfully combats its reputation as an aesthete and a wimp by reproducing the most energetic dance music formats and the heaviest industrial genres. It was very interesting to listen to experimental music recorded in high quality — for example, Therr Maitz's album Unicorn, in which light indie rock coexists with clever electronics and intricate free jazz.
No track on the album posed a problem for the MartinLogan ESL X — and it consistently delighted with its superb sound. Not every speaker is capable of this — even those in the top league.
Ultimately, the MartinLogan ESL X speakers leave a very coherent impression. They don't try to overwhelm you with power or impose their interpretation of the music. Instead, they offer a glimpse into the very essence of the recording, bringing the artist's vision and the sound engineer's skill to the forefront.
Their main strength lies in their incredible detail and naturalness. The sound is airy, transparent, and yet absolutely accurate. You hear not just the guitar, but all the nuances of the fingers touching the strings, not just the voice, but the subtle emotions in the singer's breath.
These speakers are the perfect choice for those who are tired of intrusive or tiring sound. They don't shout, they tell a story. With them, you can listen to music for hours, discovering something new in familiar tracks every time. ESL X is not just a piece of technology, but a true gateway to the world of music, where the music itself remains the focus, not the equipment.
