Another "Biasless" ESL thread?

[markusA]

I was thinking about bias supplies for my upcomming ESL build and it just hit me.
Does it really have to be so complicated?
The stators Swing around the diaphragms bias?
Why not allow for a dc-bias on the music signal from the amp and just connect both + and - to the diaphragm?
The signals are each others inverse so they should cancel out just nicely leaveing only the bias for the diaphragm?

Could it be that simple? What am I missing?

Ok, there's one caveat... I'm thinking DD amps, using a transformer you're pretty much stuck with a bias supply of some sort.

[Keith Taylor]

The purpose of the bias supply is to put a charge on the diaphragm. For this to happen the diaphragm has to be connected to something, presumably zero volts via a high value resistor in your case. You would need seriously high voltage supplies. I am not too familiar with DD amps that have dual (plus and minus) power supplies, but am no expert on the subject. Also you will lack the ability to adjust the voltage which is something ESL builders often do.

Keith

[geraldfryjr]

It is best to have a Bias supply that will stay at a constant level.

Bias supply's that are powered from the signal has been done in the past by various manufacturers but they have poor peformance as far as any type of regulation is concerned,Due to the varying levels of the signal and you don't want this.

Also depending on your coating It sometimes takes along time for the diagphram to charge and may never get to an optimum level unless you are playing them loud for a while and then when you turn it down the bias level will drop ,dropping the efficeincy even more aswell.


jer

[markusA]

I was toying with the idea.
Tube amps usually have a bias and you usually filter that out. With a DD amp you could possibly use it somehow instead of just tossing it away.