Quad ESL-63

The Quad ESL-63 is a full-range electrostatic loudspeaker that generates sound by electronically moving an ultra-thin, electrically charged film between two conductive plates. Instead of using heavy paper cones and voice coils, the large diaphragm membrane moves back and forth in a linear fashion to push air and create sound waves.

The ESL-63 was designed in the late 1970s and officially launched in 1981 by Peter Walker, the founder of Quad Electroacoustics. His goal was to create a speaker that acted as a perfect point source, utilizing concentric annular rings on the diaphragm to simulate sound emitting from a single point in space.

Because the ESL-63 relies on incredibly high voltages to drive its electrostatic panels, the diaphragm coatings and internal insulators can degrade over decades of use. Common issues include panels arcing, which produces a snapping sound, or the panels losing their charge entirely, which often requires professional rebuilding services like One Thing Audio.

No, the Quad ESL-63 is a dipole speaker, meaning it radiates sound equally from both the front and the back of the flat panel. To prevent the rear sound waves from canceling out the bass frequencies, the speakers must be placed at least two to three feet away from any back wall.