I wonder if anyone knows how Electrostatic loudspeakers can have any sort of
bass response.

An ESL is a doublet that radiates equally front and back. With a normal cone
loudspeaker on a finite baffle, the bass starts to roll off at a frequency
whose quarter-wavelength corresponds to the smallest dimension of the
baffle. Looking at the dimensions of, for example, the ESL63, the bass
should start rolling off below about 320Hz, but in fact is maintained down
to a -6dB point of 34Hz.

How is this possible? Is there some extreme EQ built-in to the ESL63 which I
am unaware of, or does the physics work in a different way for a panel
driven over its entire width or what?

Similarly, other electrostatics have small dimensions, yet can go fairly
deep in the bass, even those ultimately assisted by cone woofers.

I have Roger Sander's Electrostatic Cookbook, but he doesn't make clear how
ESL's bass response is maintained, except to use an external woofer or
savage EQ. His graphs for the response of an ESL panel shows the output
dropping from mid-frequencies, then a resonance rise at quite low
frequencies. It doesn't explain how to fill in the upper-bass/lower mid hole
except with extreme EQ. In the QUAD ELSs, I wasn't aware of any EQ.


Thanks

S.
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