QUAD Classic Series ESL - Manual (Page 2)

The Quad ESL is fundamentally different from
conventional loudspeakers and even other electrostatic
designs. Whilst most conventional speakers use cone
type drive units and a coil moving in a magnetic field,
Quad uses the full-range electrostatic principle, first
introduced in 1956. The sound is not created by a
cone but by a very thin diaphragm, less than one tenth
the thickness of a human hair. This ultra-low mass
diaphragm is coated with a conductive material and is
stretched between two fixed electrode plates. The
electrodes carry a positive charge and the diaphragm
carries a negative charge. The size of the charge on the
electrodes rises and falls to track the waveform of the
musical signal; so attracting and repelling the
diaphragm closer to and further from the electrode
plates. It is the movement of the almost mass-less
diaphragm that creates the sound we hear.
Quad’s unique ESL system takes the performance of
electrostatic loudspeakers a step further. Acousticians
have long recognised that the ideal loudspeaker
should be a point source from which the waves of
sound radiate in a fashion rather like the ripples
resulting from a pebble dropped into a lake. It is
obvious that large cones and even larger electrostatic
diaphragms cannot be point sources, so how can they
be made to behave more like the perfect loudspeaker?
Quad solved the problem with an elegant engineering
solution that was subsequently awarded a patent.
Instead of a large single electrode, Quad designed a
number of electrodes arranged as a series of
concentric rings. Each electrode is fed with a calibrated
delay line so the sound first leaves the centre of the
speaker then, after a short delay, the sound leaves the
next ring and so on. The delayed sounds build up into
a spherical waveform identical to that produced by a
theoretical point source. This innovative step brought
closer the achievement of the perfect loudspeaker.
The Quad ESL is a premiére music reproduction
loudspeaker constructed from the finest materials with
meticulous attention to detail. It reaches the pinnacle
of high-fidelity performance with an unparalleled
ability to sonically ‘disappear’, and create convincing
three-dimensional sound stages. Instruments and
vocals occupy precise, accurately sized locations in
space, giving an uncanny realism to reproduced
sound.
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The Quad
A legend in Electrostatic loudspeaker design
ESL