Reply To: Sound Lab ESL and power

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    Physical capacitors, as opposed to chemical (electrolytic capacitors), are simple devices consisting of parallel conductive surfaces separated by a dielectric insulation. In the case of SoundLab speakers, one “plate” is a bias voltage charged conductive surface consisting of a plastic film with a very high resistance conductive layer sputtered onto it. The other ‘Plate(s)” are conductive spaced wires on either side of the conductive film. Additionally, there are “window frames” that support and partition the conductive bias charged film, made with an insulating material. Air, and the window frame supports make up the speaker’s dielectric.

    IMO, the high source resistance of the bias supply, added to the very high resistance of the surface sputtered film conductor of the plastic film, creates a RC time constant of several seconds. Dr. West estimates about 10 seconds to reach equilibrium. While I agree that charging a capacitor from a low impedance source can result in a very high inrush current, with subsequent stress on the capacitor components, this is not the case with electrostatic speakers with their very long charging time constants, and minimal charging current.

    A factor that I do believe somewhat significant is the continued stress and ageing (if any) on the dielectric components subjected to a continuous high voltage field. While the air dielectric poses no degradation problem, the material used to frame and insulate the conductive film is of concern to me. For that reason alone, I unplug my five 845 speakers when not in use. My brother, on the other hand, having 10 SoundLab M1’s in a large home theater system, leaves his running all the time, with no apparent degradation.

    As always, UMMV