Only a handful of manufacturers have ever managed to build a production electrostatic loudspeaker. Furthermore, QUAD are unique in producing a point-source, full-range Electrostatic Loudspeaker.
The ESLs are widely regarded as the most neutral, best imaging, most transparent and accurate loudspeakers in the world.
They produce a window on music without adding any character of their own - and can be listened to for hours on end, without ever becoming tiring on the ears.
Quite simply, they are totally addictive and unlike anything you've ever heard before. They remain in a league of their own when it comes to real music and the latest models of ESL 988 & 989 have won a stream of international awards for sound quality, including the prestigious Diapason D'Or and two 'Golden Ears'.
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ESL Inside The ESLs work in a very different way to conventional loudspeakers. For those who don't know, here's a brief explanation of the principle. Whilst most speakers work with a cone type drive unit, the ESLs use a very thin membrane, one-tenth the thickness of a human hair. This MYLAR diaphragm has a special conductive coating and is stretched between two electrode plates. Relative to earth, both electrode plates have a high positive charge (+5000v), but there is a slight difference between the charge on each electrode. It is this difference that causes the negatively charged membrane to be more attracted to one than another, thus causing the movement of the diaphragm. |
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diaphragm is mounted on an open frame and is thus free of any coloration
from a cabinet. Because the diaphragm acts as a full range driver, there
is no need for a crossover. There are no discontinuities in the frequency
response curve, so you get the full music spectrum, as it was recorded.
The ESLs do much more than reproduce the full range - and this is where
all other electrostatic speakers stop. Acousticians have recognised for
a long time that an ideal loudspeaker should be a point source from which
sounds waves ripple like a pebble in a lake. Ordinarily, an electrostatic
would fall at this hurdle, but not the QUAD ESLs.
By using a series of concentric anodes, rather than just two plates, the
Quads are able to produce a spherical sound pressure pattern. A series
of electrode rings are fed with delay lines, so each ring responds to
the change in current a split second after the previous ring, creating
movement in the diaphragm identical to the 'ripple in the pond'. The 988s
and 989s both use this principle, with the 989s having additional panels
to give a robust bass performance.
The Quad ESL is the only speaker to use this method so if you want the
finest, most accurate sound sound in existence - better choose QUAD.
How the ESLs Work:
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1. A perfect point source produces a spherical wave pattern. |
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2. The air particle movement at a plane some distance from the source. |
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3. An identical movement in the ESL membrane produces and identical wave front. |
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4. The membrane carries a constant charge. The charge on the electrodes fluctuates according to the music signal. |
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5. The music signal is fed first to the center section, then to each ring in turn. |