Quad ESL-57

Introduced in 1957 by Quad Electroacoustics, the ESL-57 was the world's first commercially available full-range electrostatic loudspeaker. It completely abandoned the traditional moving-coil design in favor of a flat, ultra-thin Mylar diaphragm suspended between conductive plates.

Because the ESL-57 is a highly capacitive load that dips to very low impedance at high frequencies, it requires an extremely stable, high-quality amplifier. Inappropriate amplifiers can easily overheat or trigger protective circuits, and historically, Quad recommended using their own Quad II tube amplifiers to drive them.

The original speakers are notoriously delicate and cannot be played at extremely high volumes without risking internal electrical arcing, which destroys the conductive panels. Furthermore, the Mylar diaphragms and conductive coatings deteriorate over decades of use, meaning almost all vintage units today require professional rebuilding.

The electrostatic transducer technology allows the ESL-57 to produce remarkably accurate, phase-coherent sound with virtually no cabinet coloration. While it lacks deep bass extension and cannot play at high volumes, its midrange clarity and transparency are legendary among audiophiles.