ESL-63 (back ups)

About the ESL-63 (back ups)

The Quad ESL-63, introduced in 1981, is a significant electrostatic loudspeaker featuring a diaphragm divided into concentric circular areas fed by delay lines, creating a spherical wavefront that acts as an acoustical point source. This design results in near-perfect phase coherence and wide treble dispersion, enhancing the listening sweet spot. It includes sophisticated protection circuits to prevent damage from overloads, though some solid-state amplifiers may be sensitive to its shorting protection. The speakers have a nominal impedance of 8 ohms, sensitivity of 86dB SPL at 2.83V/1m, and a frequency response from 35 Hz to 20 kHz (-6dB points). They weigh approximately 18.7 kg each and measure 36" H x 26" W x 6" D. Originally Refurbished units are available, often retaining original colors or customized finishes. The speakers require amplifiers capable of delivering 50 to 100 watts for optimal performance. Despite some limitations in bass extension and maximum volume, the ESL-63 remains a classic with a distinctive sound signature and advanced electrostatic technology.