stator spacing/voltage bias

[tade]

What is the way to determine the best voltage bias for an esl speaker. Is there a simple formula, something like x volts per mm spacing?

[I_Forgot]

The best voltage to use is the highest voltage that doesn't cause audible corona discharge. That is a function of the humidity of the air in the space, and the mechanical nature of the stators you use. Stators with sharp edges will exhibit corona discharge at lower voltages. Sharp edges and points will tend to concentrate the electric field in their immediate vicinity and produce blue sparks that can be seen with the lights out and can often be heard as a hissing or whining sound coming from the location of the spark.

This and overall safety are the two main reasons to use a variable voltage bias supply such as the type shown here: Bias Supply
You can adjust the output from about 500 V all the way to 6 kV if you use the 6000V DC-DC converter module.

Dry air undergoes dielectric breakdown at about 3 MV per meter,- i.e. 3kV per mm. Humid air will breakdown at lower voltage.

If your stator to diaphragm spacing is 2 mm, 6 kV is the highest bias voltage you can ever hope to use (unless you seal the speaker and flood it with a gas that has higher breakdown voltage than air).

TD

[tade]

i hadnt thought abotu those sharp edges, but makes perfect sense now. many thanks!