Specifications

The electrostatic starts with a very thin (half mil or less)
diaphragm made of Mylar or a similar material, to which a light
coating of mildly conductive substance such as graphite has been
applied. This diaphragm is suspended on a rigid frame and
sandwiched between two stationary conductive grids (usually
perforated metal plates) called stators.
FRAME
REAR STATOR
RESISTOR
TRANSFORMER
+
--
TO
AMPLIFIER
TO BIAS
VOLTAGE
SUPPLY
[PERFORATED
METAL PLATE]
FRONT
STATOR
CONDUCTIVE
DIAPHRAM
PUSH-PULL ELECTROSTATIC
[TOP VIEW CROSS-SECTION]
Spacing exaggerated to show detail
A DC charge of high voltage (in the thousands of volts) but very
low current, known as the bias voltage, is applied to the
conductive diaphragm and kept constant. A step-up transformer
is introduced to increase the usable voltage of the amplifier's
output (while simultaneously decreasing the current), and the two
ends of the transformer's output coil are connected to the two
stators.
As the amplifier produces a continuously varying AC voltage,
(the amplified music signal), the charge on the two stators will
also continuously change in synchronization with the music; and
since the two stators are connected to two different ends of the
transformer's output, one stator will take on a predominantly
negative charge at the same time and to the same extent that the
other stator takes on a predominantly positive charge. The
constant-charge diaphragm will thus undergo a continuously
changing state of attraction to and repulsion from the two stators
as their polarization changes, and it is this motion that excites the
air to the front and rear of the speaker and produces sound.
Electrostatic
Loudspeakers
11