capacitor dielectric bias

Vandersteen, among others, also uses a DC bias on some of his crossover filter caps.

Here's a pic of the 5A crossover with its 27V. stack of 9-Volts.

http://i89.photobucket.com/albums/k220/jeffreybehr/0%20Vandersteen%205as/Boardtop1_1280w.jpg
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Biasing of electrolytics is even more critical than that of film. If not biased, they will distort. This has led to a bad reputation for electrolytics, one not deserved if they are actually treated properly.

I have only seen this phenomina with high capacity ceramic capacitors, not in electrolytics.

Liguy, it is very well known in electrolytics. If an electrolytic is used as a coupling cap, the cap must be biased with a DC voltage that is larger than the AC signal it is being used to couple. Electrolytics *really* don't like being reverse-biased, which would happen on part of the waveform if the first part of this statement is not realized.

Now in crossovers, 'non-polar' electrolytics have been used for years, but that technique produces distortion because of this bias issue. If they are to be used successfully in a crossover, the caps have to be biased with a battery. When this is done they easily operate with the performance of film caps.

Say what dude.