Martin Logan ElectroMotion ESL Manuel De L'utilisateur page 16

excite the air and create music. The stator's job
is to remain stationary, hence the word stator,
and to provide a reference point for the moving
diaphragm. The spacers provide the diaphragm
with a fixed distance in which to move between
the stators.
As your amplifier sends music signals to an
electrostatic speaker, these signals are changed
into two high-voltage signals that are equal in
strength but opposite in polarity. These high
voltage signals are then applied to the stators.
The resulting electrostatic field, created by the
opposing high voltage on the stators, works
simultaneously with and against the diaphragm,
consequently moving it back and forth, producing
music. This technique is known as push-pull
operation and is a major contributor to the sonic
purity of the electrostatic concept due to its
exceptional linearity and low distortion.
Since the diaphragm of an electrostatic speaker
is uniformly driven over its entire area, it can be
extremely light and flexible. This allows it to be
very responsive to transients, thus perfectly tracing
the music signal. As a result, great delicacy,
nuance and clarity is possible. When you look at
the problems of traditional electromagnetic drivers,
you can easily see why this is so beneficial. The
cones and domes which are used in traditional
electromagnetic drivers cannot be driven uniformly
because of their design. Cones are driven only
at the apex. Domes are driven at their perimeter.
As a result, the rest of the cone or dome is just
"along for the ride". The very concept of these
drivers requires that the cone or dome be perfectly
rigid, damped and massless. Unfortunately, these
conditions are not available in our world today.
To make these cones and domes move, all
electromagnetic drivers must use voice coils wound
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on formers, spider assemblies, and surrounds to
keep the cone or dome in position (see figure 15).
These pieces, when combined with the high mass
of the cone or dome materials used, make it an
extremely complex unit with many weaknesses and
potential for failure. These faults contribute to the
high distortion products found in these drivers and
is a tremendous disadvantage when you are trying
to change motion as quickly and as accurately as
a loudspeaker must (40,000 times per second!).
Figure 14. Cut away view of an electrostatic
transducer. Notice the simplicity due to minimal
parts usage.
Figure 15. Cut away view of a typical moving
coil driver. Notice the complexity due to the high
number of parts.