You might think that the photo shows a pair of electric radiators. But no, they are actually some of the finest loudspeakers ever designed.
And the design dates from 1957!
I have no interest in vintage equipment for its own sake, and I'll use whatever sounds good, whatever its age. I tell you that because I don't want you to think I'm saying these speakers are good because they are old. That would be nonsense. They are good because their design is amazing. And, well-maintained of course, their age is immaterial.
The photo shows examples of the Quad ESL 57 electrostatic loudspeaker. '57' because the design dates, as I said, from 1957. If you want something more up-to-date then there's also the ESL 63 to consider :-)
Now, Question Number 1 is why are these speakers so good?
The answer to that comes from another question - why are moving coil loudspeakers so bad? (Almost all loudspeakers are of the moving coil design. You have some right there in your studio, and your living room, and your car, and tiny ones plugged into your iPod.)
The problem with moving coil loudspeakers is mainly to be found in the low-frequency drive unit, or woofer. The diaphragm has to be big to shift a lot of air. It has to be light so it can move easily. It has to be stiff so that it doesn't bend and produce distortion. And it has to satisfy all three of those conflicting requirements, which it can't.
Modern moving coil loudspeakers are amazingly good, but there is always the problem of transmitting the movement of the voice coil in the center of the drive unit, all the way to the edge of the diaphragm, without the diaphragm bending. This problem is inherent to the design.
But the diaphragm of the electrostatic loudspeaker can be driven over its entire surface area. It can be extremely light, yet still not bend. The result is a distortion-free, airy and accurate sound. The motto of Quad, the manufacturer, was and continues to be "The closest approach to the original sound". With just cause.
So now for Question Number 2 - If electrostatic loudspeakers are so good, why do we still use moving coil designs?
One answer to that is that it is cheaper to produce moving coil loudspeakers. Or to put it another way, electrostatic loudspeakers can't be produced cheaply.
Another is that electrostatics don't handle high levels and lots of bass so well as moving coils.
Another is that they are bi-directional, so you have to consider where the sound from the rear goes.
Another is that they need mains power.
Another... Well that's probably enough. They are simply not as practical as the moving coil.
Although not as accurate, many people prefer the 'speakery' sound of the moving coil design.
I am to an extent eulogizing the electrostatic loudspeaker, and it is a fact that I don't have them in my home. But I certainly do recommend you take any opportunity you can to listen to some. You will be amazed how non-speakery loudspeakers can be!
Now for some more of those lovely photos from significantsound...
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