Electrostatic loudspeaker acoustics

Although loudspeakers designed with the traditional approach are popular for many reasons, there are also alternatives – for example, exotic but exciting electrostatic loudspeakers such as the Martin Logan ElectroMotion ESL X!

The monaural speaker doesn't attract as much attention in the same way as a bulky electrostatic speaker. This has been noticed Martin Logan, The company, founded in 1983, has become known for its hybrid speakers, which have a dynamic element for low-frequency reproduction and the rest of the frequency range is reproduced by a curved electrostatic element.

Although the electrostatic loudspeaker element is considered to be an exotic modern technical creation, in fact Siemens and others were working on the development of this type of loudspeaker element as early as the 1920s. Since then and to this day, the electrostatic principle has attracted the possibility of producing sound by moving the loudspeaker membrane precisely and uniformly over its entire surface area without the resonance problems of dynamic elements.

In short, static technology involves placing a thin, electrically conductive sheet between two fixed, acoustically perforated metal plates, the stators, that are opposite in tension.

Because the plus and minus terminals of the output signal are connected to corresponding metal plates, the alternating electric field causes the film to pull away from or toward the metal plates. And when the film is electronically controlled over its entire surface area, the oscillation motion is ideally controlled, and at the same time the distortions remain small, with the pulse response being extremely fast. This completely eliminates the need for a speaker enclosure, one of the biggest drawbacks of conventional speakers.

Electrostatics are, in their own way, a kind of immersive audio system. They create a strong and precise spatial sound and offer a more immersive perspective on the musical work’s acoustic world. At least, that is the case if both the electrostatic speaker and the audio disc being listened to are technically well-executed.

On the other hand, electrostatic speakers also have their own limitations, with which one can not only get along but also find solutions. The rather modest movement deviation of the electrostatic film combined with its radiation pattern is not always sufficient to create convincing bass reproduction. Therefore, an additional dynamic element is often added to support the bottom end, as otherwise the film surface area would grow to an unreasonably large size.

Martin Logan's ElectroMotion ESL X It is a hybrid speaker featuring two bass units alongside a large electrostatic diaphragm. More specifically, the speaker’s XStat diaphragm has a radiation area of 2,244 square centimeters at its lowest frequencies, and it is supported by two 8-inch wide-band bass units mounted in a non-resonant asymmetrical reflex enclosure. Overall, the implementation is still relatively compact, and the ElectroMotion ESL X measures 150.3 centimeters in height, 52.6 centimeters in depth, and only 23.8 centimeters in width. The weight of the speaker is also still relatively moderate at 23.6 kilograms compared to its dimensions.

In the Martin Logan ElectroMotion range, the ESL X is the largest speaker, and as usual, the manufacturer has borrowed technology from more prestigious series. The speaker’s frequency response extends from 41 Hz to 22 kHz (±3 dB in steps), and its sensitivity is 91 dB (2.83 volts/1 meter). The crossover frequency between the electrostatic panel and the dynamic bass drivers is 400 Hz, and the nominal impedance of the speaker is six ohms, although it drops quite low to 1.6 ohms at 20 kHz. The manufacturer recommends power outputs of 20–400 watts per channel.

In addition to its powerful performance, the ElectroMotion ESL X also impresses with its appearance. The XStat panel technology is focused on ensuring that the metal mesh of the panel is as thin as possible without affecting the sound quality. Therefore, the ESL X’s XStat panel is almost transparent, making it almost disappear into the listening room!

Watch this introduction video for Martin Logan's ElectroMotion series:

Martin Logan ElectroMotion ESL X speakers cost 5,699 euros per pair, and you can find them From the audio store!