Much like electrostatic loudspeakers, electrostatic headphones feature extremely thin, membrane-like diaphragms, to which a conductive coating is applied, with the diaphragms suspended between sets of mesh-like panels called stators. A very high bias voltage (580V in many models) is applied to the diaphragm, while an also high-voltage push-pull audio signal is fed to the stator panels. As the audio signal flows back and forth, the diaphragm is first repelled from one stator and attracted to the other (and then vice versa as the signal swings back and forth according to the demands of the music).
The benefits of electrostatic designs include extremely good responsive and exceptional transient speed, plus typically low distortion, given that diaphragms are very low in mass and driven over their entire surface area. Electrostatic headphone designers seek performance advances by looking for ways to reduce the mass of conductive diaphragms, to increase the openness of airflow through the mesh-like stator panels, to improve the rigidity of driver frames, and to look for ways and means of better controlling diaphragm-membrane resonance.
An Exemplary Model
Stax SR-009 ($5250) staxusa.com
For many decades the Japanese firm Stax has been the acknowledged leader among electrostatic headphone makers, so that for some headphone enthusiasts the words “Stax” and “electrostatic” seem almost synonymous. The SR-009 is the best electrostatic headphone Stax has ever made, which is saying a mouthful when you consider the legendary models the firm has produced over the years. The SR-009 offers levels of transparency and detail that beggar both description and belief, and for this reason (and others) many audio journalists consider the SR-009 the best all-around headphone in the world.
The SR-009 is one of the most transparent and faithful-to-the-source transducers on the planet, offering mind-bending transient speed, wide- range frequency response, and both subtle or explosive dynamics on demand. As many critical listeners can attest, one does not listen to the SR-009 so much as through it, so that the sound one hears is governed more by the source and amplification components in use than by the headphone itself.
The SR-009 is every bit as revealing of inner details and textural nuances as today’s most accomplished loudspeakers, regardless of price. If $5250 seems a huge sum to invest in headphones, consider that to reach this same zenith of performance in loudspeakers could easily cost between 10x to 30x more. Caveat: Be aware that the SR-009 will require a (typically expensive) dedicated electrostatic headphone amp to give of its best.