Adman227, your quote (from Montytx) is why I said I thought there was some confusion over power vs. current. Again, I recommend this site: http://www.allaboutcircuits.com/vol_1/index.html . |
Nsgarch, you could have used a better example than an ESL. How about a B&W? ESLs are neither looking for current or voltage- they are expecting constant Power. That is why tube amps generally sound better on them too, so long as they are able to make the constant power into all frequencies. The idea of constant voltage appears to have nothing to do with the way we hear. Its odd how it keeps showing up. |
Nsgarch, I am aware that the impedence goes down with rising frequency, but that does not necessarily mean that the power requirement and hence the current demand goes up. usually, the amount of high frequencies is very low and therefore the voltage necessary to move the membrane is less also, therefore not much power necessary to do the job. since, as you stated, there really isn't really much work done by these 'capacitors' not many amps are necessary. Again, as you say, it is the varying voltage on the membrane between the stators that cause the membrane to move, thus making sound. Tht is what i mean by 'stats are voltage driven'. Not much energy is used through that action. Most of the energy is used in maintaining the constant voltage in the stators through their circuits. |
Inpep, voltage is defined as the POTENTIAL to do WORK by MOVING electrons from one point to another. In an electrostatic speaker, electrons do not move across the gap between the membrane and the stator(s) unless of course the two happen to touch, or the current builds up to the point where there is and electrostatic discharge -- arcing -- in which case the speaker is damaged by a hole being burned in the membrane. The membrane's movement is generated solely by the (alternating) attraction/repulsion of the charged surfaces, nothing else. A constant high voltage (potential) is maintained on the stators, generally on the order of 20,000 volts. You don't get a shock because there's virtually no current associated with it, no capability of those volts to push any electrons through you ;-) The membrane has a constant potential as well, but it changes from + to - at whatever frequency the signal dictates. The faster the polarity alternates, the more current is required. That's how AC works, only in reverse. It produces current by CHANGING polarity, and NOT by pushing electrons through miles of wire (which BTW is what we'd have if Westinghouse hadn't prevailed over Edison ;-) ANYWAY, Ohms Law says I = V/R. Current = Volts divided by Resistance. Higher frequencies require more current to produce them (just the opposite of an AC generator) and from Ohms formula, if I gets bigger, and V stays constant, then R must get SMALLER. And there you have it. Yes, the amp must provide more power (watts) at higher frequencies, but only as much as necessary to increase the CURRENT to the membrane. The membrane doesn't need volts, because very little WORK is being done to move it. P (watts) = I (Current) x V (Volts) So if an amp can deliver watts which consist mostly of current instead of volts, that'll be just fine for a stat. In most (high or low wattage) SS amps, the current they deliver is rather a smaller proportion of each watt. Whereas, a tube amp's watts consist of a rather higher proportion of current in each watt. So if all you're after mainly is current, why not choose a lower wattage tube amp? And you get the bonus (IMO) of tube sonics to boot ;-) . |
