Electrostatic Loudspeakers

Abstract

New materials and techniques have made possible the design of useful electrostatic loudspeakers. High polarizing and signal potentials across air gaps which are large enough to permit diaphragm excursions of a magnitude necessary for the production of low frequencies, together with an acoustically transparent stationary electrode and a diaphragm which is light compared with the mass of the entrained air, result in unusually good pressure response and phase response characteristics as well as a useful amount of power from relatively small areas. The only resonances are those which arise between the compliance of the diaphragm material and the mass of the entrained air, and these can be made to occur below the useful range of audiofrequencies. The active radiating area is made to retract with frequency to preserve good polar response and to improve the impedance characteristic, by making the distributed capacitance of the loudspeaker part of a resistance-capacitance network. The extremely smooth pressure response resulting from the absence of resonances makes the loudspeaker suitable for the production of transient acoustic signals. Response curves and design data are presented.