MartinLogan Loudspeaker Systems - Manual (Page 13)

How can sound be reproduced by something that you are
able to see through? Electrostatic energy makes this possible.
Where the world of traditional loudspeaker technology
deals with cones, domes, diaphragms and ribbons that
are moved with magnetism, the world of electrostatic
loudspeakers deals with charged electrons attracting and
repelling each other.
To fully understand the electrostatic concept, some background
information will be helpful. Remember when you learned
in a science or physics class that like charges repel each
other and opposite charges attract each other? Well, this
principle is the foundation of the electrostatic concept.
An electrostatic transducer consists of three pieces: the stators,
the diaphragm and the spacers (See Figure 14). The diaphragm
is what actually moves to 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 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!).
E
LECTROSTATIC
A
DVANTAGES
Electrostatic Advantages 13
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.