A New Direction: The Electrostatic Loudspeaker

Electrostatic loudspeakers took sound reproduction in new directions. These speakers generally consist of four main parts:

• a power supply that provides electrostatic charge (think rubbing your feet on a carpet and touching a doorknob)
• a rigid plate (or plates) to hold the electric charge
• a flexible plate to act as diaphragm (only a few microns thick) which makes the music

The diaphragm is driven by a step-up transformer to multiply the voltage output from your amplifier to a level high enough to move the flexible plate. Although patented in 1929, the electrostatic loudspeaker did not reach commercial success until the 1956 with the appearance of the British-made Quad ESL-57. Electrostatic speakers (especially the old Quads) are renowned for their beautiful midrange and their frailty. However, if you put more than 20 Watts to them, or try for more than 100 dB of sound, and they are toast. They are the Jaguar XKE of the speaker world--beautiful, but fragile.