Understanding how STAX electrostatic earspeakers work will explain why they sound so drastically superior.
The new STAX SR-LAMBDA/SRM-1Mk2 Professional Earspeaker System provides serious audiophiles unprecedented realism that even the most sophisticated loudspeaker systems cannot provide. In applications where transparency, accurate phasing, and natural tonal balance are required, the SR-Lambda Professional Earspeaker System surpasses any other acoustical transducer.
The SR-Lambda Professional Earspeaker System was originally designed by the West German automotive manufacturer Daimler-Benz for their research and quality control engineers to use in car noise analysis. From a musical point of view, the end result of the SR-Lambda Professional is so outstanding that STAX is now making it available for home & studio use.
If we speak of a headphone, it usually means a dynamic one employing a dynamic transducer. In the dynamic transducer the driving force is applied.
Only to the one part of the diaphragm which, therefore, must be stiff enough not to be deformed by air load. However, stiff materials considerably increase the diaphragm mass resulting in significant deterioration of transient response. In addition, the ununiform force applied over the diaphragm area leads to what is called cone break-up”. Hysteresis distortion caused through the magnet inevitable in the dynamic transducer cannot be ignored, either.
The electrostatic transducer adopted in the STAX earspeakers consists of two parallel- arranged fixed electrodes and several microns thick (2 microns in the SR-Sigma, the SR-Lambda and the SR-X/Mk3 and the SIR-5N. 4 microns in the SR-84 and the SR-34) high-polymer film diaphragm suspended in the middle of the electrodes. The low-mass film diaphragm is supplied with biasing voltage from the energizing adaptors or from the SRM-1/Mk2. In the electret type earspeakers like the SR-84 and the SR-34 the diaphragm is permanently charged minus. When the fluctuating voltage of the audio signal is applied to the electrodes, the diaphragm is pulled by the electrode which has the opposite charge of the diaphragm’s and simultaneously pushed by the other electrode which then has the like charge of the diaphragm’s. The continuous flow of alternating voltage in interpretation of audio signals causes the diaphragm to vibrate in faithful compliance with the amplifier output without time lag, assuring undistorted sound waves. This is why the STAX electrostatic earspeakers sound so good. The figure above shows the driving mechanism of the SR-84 and the SR-34.
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SR-34: Cost vs. Performance Electret Earspeaker
SR-84: Lambda Junior Electret Earspeaker
SR-Lambda: Semi-Panoramic Imaging Electrostatic Earspeaker
SR-Sigma: Panoramic Imaging Electrostatic Earspeaker
Also see: Stax SRX-II Electrostatic Earspeaker system (April 1975)