spritzer
Member of the Trade: Mjölnir Audio
- Joined
- Aug 22, 2002
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Quote:
I think you aren't on the same page as me. The force goes to moving the diaphragm through electrostatic force with a bias of DC and AC driving voltages. The power is used to drive the film but since it's AC we a re dealing the impedance is variable and because the electrostatic force is so weak (drops by the square of the distance, i.e.1m x/1 and 2m x/4 and 3m x/9 etc.) that you need plenty of power to move it just a small distance. Add to that the drivers get more efficient the bigger they get (line source) so we have very small drivers with large spacing that requires heaps of power to get going.
A Stax Lambda is 120pF and if you drive them at 600v (half maximum voltage) at 20kHz you need a slew voltage of 75.4 v/us. The current needed is the SR*capacitance so 9.05mA.
Originally Posted by g1981c /img/forum/go_quote.gif that square root thing i believe does not apply to infinite plane ... so where does the power go, it must go somewhere ... are you saying the power factor of electrostatic cans is close to zero ? so you're simply charging and discharging the capacitance without doing useful work ? ? |
I think you aren't on the same page as me. The force goes to moving the diaphragm through electrostatic force with a bias of DC and AC driving voltages. The power is used to drive the film but since it's AC we a re dealing the impedance is variable and because the electrostatic force is so weak (drops by the square of the distance, i.e.1m x/1 and 2m x/4 and 3m x/9 etc.) that you need plenty of power to move it just a small distance. Add to that the drivers get more efficient the bigger they get (line source) so we have very small drivers with large spacing that requires heaps of power to get going.
A Stax Lambda is 120pF and if you drive them at 600v (half maximum voltage) at 20kHz you need a slew voltage of 75.4 v/us. The current needed is the SR*capacitance so 9.05mA.