Quad Esl-57

In very good condition, working as tested. Can be tested pre purchase. Complete with original owners manual. QUAD ESL-57 (originally launched simply as the QUAD Electrostatic Loudspeaker) is the world’s first production full-range electrostatic loudspeaker. Introduced in 1957 by the Acoustical Manufacturing Co. (later QUAD Electroacoustics) and produced until 1985, it is widely considered one of the most important and revered audio innovations of the 20th century The Core Technology Unlike conventional speakers that use cardboard cones and magnets, the ESL-57 utilizes an ultra-thin, electrically charged Mylar diaphragm suspended between two perforated metal plates (stators). High-voltage power supplies charge the internal components to thousands of volts, causing the diaphragm to move instantly in response to the audio signal. Key Specifications Type: 3-panel two-way dipole loudspeaker (Two outer bass panels, one central treble/midrange strip). Frequency Range: 45 Hz to 18 kHz. Nominal Impedance: Highly variable, averaging 15 to 30 Ohms but dropping below 2 Ohms at high frequencies. Sensitivity: Approximately 84 dB. Dimensions: 880mm Width × 790mm Height × 270mm Depth. Weight: 16–18 kg per speaker. Sonic Strengths and Limitations The Magic: Because the diaphragm has almost no mass, the speaker delivers legendary midrange transparency, lightning-fast transient response, and realistic vocal reproduction. The speaker projects sound forward and backward (as a dipole), creating a deep, natural soundstage. The Caveats: The physical design restricts its bass extension, meaning it cannot produce deeply impactful sub-bass for modern electronic or rock music. It also features a narrow horizontal "sweet spot," requiring precise positioning. Amplifier Pairing & Arcing Danger Because the speaker presents an intense capacitive load to amplifiers, choosing the right power source is critical. Vintage low-power tube amplifiers—like the original QUAD II monoblocks (15W per channel)—are widely considered the safest and most musical match. Feeding too much voltage into an ESL-57 can cause arcing, where electricity sparks straight through the thin Mylar film, permanently burning a hole in the panel. High-power modern solid-state amplifiers must be used with severe caution or fitted with internal protection circuits