ELECTROSTATIC LOUDSPEAKER (ESL) ANIMATION

Thickness and motion are exag- gerated for clarity above.

Ben Franklin reasoned long ago that opposite charges are attracted together, and like charges are repelled apart. In an ESL, the membrane has one charge, and on each side of it are plates called stators that have a different charge. The difference in charge pushes the membrane.

In the animation, each stator alternates between positive (red) and negative (black) voltage, as under the influence of an audio signal. The voltage continually reverses, moving the membrane back and forth, creating sound waves that are emitted through holes in the stators.

The polarities of the two stators are always opposite one another, so while electrostatic force is pushing the membrane from one side, it is also pulling it from the other. This makes the force quite linear, reducing distortion to inaudible levels, as long as the resting membrane gaps are equal. It also makes the speaker louder.

An ESL's highly linear driving force is spread out evenly over the entire membrane, and the mem- brane is extremely light -- lighter than the air it is pushing. As a result, the membrane moves with near-perfect coherency and accuracy, remaining flat and moving without a trace of breakup.

The upshot is that the sound waves made by the membrane exhibit practically no harmonic or intermodulation distortion, and can be given a frequency response that is both flat and smooth.

Note: The above explanation is market-neutral, but JansZen ESL's have design features that make them superior to the others under most conditions. For assistance in locating or interpreting specific comparison information, please feel free to contact us by phone.

Interestingly and importantly, the way an ESL converts an audio signal to sound is the exact inverse of how a recording microphone converts sound into an audio signal. In a microphone, pressure creates voltage, and in an ESL, voltage creates pressure. This contributes to the excep- tional accuracy of ESL's. It is not the case for cone speakers, where electrical current supplies non-linear force to a multiple spring-mass-damper system.

Lastly, because an ESL better represents a recording's phase information, an even greater increase in realism occurs with recordings that have been made in a way that conserves a performance's initial phase information.

The situation is very different with cone speakers. One generally hears substantial contrasts in tone when listening to different designs. A large part of the explanation for this is that a heavy, spring- loaded coil pushes and pulls the center of a high mass radiating surface. There are practical limits to how accurately the coil movement can follow an audio signal, and then to how well the cone movement can follow the coil movement.

A cone speaker's resulting lags, displacements and resonances alter the sound in several ways, and add sound that was not part of the original recording. These effects can be minimized, but not eliminated or even made inaudible. Each cone speaker design reflects a particular set of choices and tradeoffs made while engineering around limitations that ESL's do not have.