QUAD ESL-63

Commentary

QUAD spent a quarter of a century to complete the speaker system.

This speaker consists of two fixed electrodes and a diaphragm placed between them.
When a high voltage is applied to the vibrating membrane to generate static electricity and an audio signal is sent to the fixed electrode, a Coulomb force acts between the vibrating membrane and the fixed electrode to move the vibrating membrane and produce sound.
This method does not require any strength because the diaphragm moves uniformly over the entire surface. It can be set to a very light diaphragm and can be driven with very little energy. It also has advantages such as good impedance matching with air and no need for a cabinet.
The ESL-63 has succeeded in generating all frequencies at one point based on this system.

Since a general electrostatic speaker is plane driven and tends to be plane wave, the listening position was limited.
To solve this problem, in the ESL-63, the fixed electrode is divided into seven concentric rings and a delay circuit is set for each of them. By generating a signal delay of approximately 24 μ sec per stage from the inner circumference to the outer circumference, for a total of approximately 168 μ sec, we have succeeded in generating a spherical wave from a flat vibrating membrane. By this, the sound source is located approximately 30 cm behind the vibrating membrane and can freely respond to changes in directivity caused by changes in frequency.

In addition to using a new material, Melinex, the manufacturing error is limited to ± 1/2dB compared to the reference machine. In order to realize high sound quality, it adheres to the QUAD policy.

It has two built-in protection circuits to deal with unexpected accidents.
It is equipped with a limiter that limits the input voltage and a circuit that detects abnormal input signals or momentary short circuits and does not send them to speakers.

Model Rating

Type	Condenser type, floor type
Nominal impedance	8 Ω
Playback frequency band	35 Hz to 20 kHz (-6dB at 35 Hz, -6dB at 20 kHz)
Output sound pressure level	86dB/W/m
Sensitivity	1 μ bars/V/m (86dB/2.83 Vrms)
Max Input	Maximum continuous input voltage : 10 Vrms Maximum peak input during program to obtain distortionless output : 40 V Maximum allowable peak input : 55 V
Maximum power output	2N/m2(2m on axis)
Directional property	125Hz:5dB 500Hz:6.4dB 2kHz:7.2dB 8kHz:10.6dB
Power input	100 ~ 120 VAC / 200 ~ 240 V, 50Hz/60Hz
External dimensions	660 mm wide x 925 mm high x 270 mm deep (including 150 mm base plate)
Weight	18.7kg