MartinLogan The Quest Speaker System Electrostatic Concept, An Electrostatic Transducer

The Electrostatic Concept

How can sound be reproduced by something that you are			music. This technique is known as push-pull operation and
able to see through? Electrostatic energy makes this			is a major contributor to the sonic purity of the electrostatic
possible.			concept due to its exceptional linearity and low distortion.
Where the world of traditional loudspeaker technology			Since the diaphragm of an electrostatic speaker is uni-
deals with cones, domes, diaphragms and ribbons that are			formly driven over its entire area, it can be extremely light
moved with magnetism, the world of electrostatic loud-			and flexible. This allows it to be very responsive to tran-
speakers deals with charged electrons attracting and			sients, thus perfectly tracing the music signal. As a result,
repelling each other.			great delicacy, nuance and clarity is possible. When you
To fully understand the electrostatic concept, some back-			look at the problems of traditional electromagnetic drivers,
			you can easily see why this is so beneficial. The cones and
ground information will be helpful. Remember when you			domes which are used in traditional electromagnetic
learned, in a science or physics class, that like charges			drivers cannot be driven uniformly because of their design.
repel each other and opposite				Cones are driven only at the
charges attract each other?	An Electrostatic Transducer			apex. Domes are driven at
Well, this principle is the				their perimeter. As a result,
foundation of the electrostatic				the rest of the cone or dome
concept.				is just "along for the ride". The
				very concept of these drivers
An electrostatic transducer	Diaphragm			require that the cone or dome
consists of three pieces: the				be perfectly rigid, damped
stators, the diaphragm and the	Spacer			and massless. Unfortunately
spacers. See Figure 1. The			Stator	these conditions are not
diaphragm is what actually				available in our world today.
moves to excite the air and
create music. The stator's job is				To make these cones and
to remain stationary, hence the				domes move, all electromag-
word stator, to provide a	Figure 1. Cut away view of an electrostatic transducer.			netic drivers must use voice
reference point for the moving				coils wound on formers,
diaphragm. The spacers	Notice the simplicity due to minimal parts usage.			spider assemblies, and
provide the diaphragm with a				surrounds to keep the cone
fixed distance in which to move				or dome in position. See
between the stators.	An Electromagnetic Transducer			Figure 2. These pieces, when
				combined with the high mass
As your amplifier sends music			Dust Cap	of the cone or dome materials
signals to an electrostatic	Surround Cone			used, make it an extremely
			Voice Coil Former
speaker, these signals are				complex unit with many
changed into two high-voltage				weaknesses and potential for
signals that are equal in				failure. These faults contrib-
strength but opposite in			Spider	ute to the high distortion
polarity. These high voltage				products found in these
signals are then applied to the				drivers and is a tremendous
stators. The resulting electro-				disadvantage when you are
static field, created by the	Basket Assembly		Magnet Assembly	trying to change motion as
opposing high voltage on the				quickly and as accurately as
	Magnet	Voice Coil	MagneticGap
stators, works simultaneously				a loudspeaker must (40,000
with and against the dia-	Figure 2. Cut away view of a typical moving coil driver.			times per second!).
phragm, consequently moving	Notice the complexity due to the high number of parts.
it back and forth, producing

Quest User's Manual Page 5