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In Reply to: RE: Attn: andy_c re: electrostat impedance curves posted by E-Stat on May 04, 2009 at 14:30:06
Hi
I'm not Andy but i have made many electrostatic speakers back in the old days.
For a one way electrostatic system, one would expect the bell curve you mention.
At the low end, the impedance droops because of the step up transformers parallel inductance (same thing as in a tube amplifier typically).
Up high, the impedance falls because of the parallel C the speaker presents as a load. In the mid of the curve, the resistive component dominates, made from the Rdc of the transformer primary, secondary and other resistances.
Essentially the driver itself is a C with very little else but since you need a large step up ratio to get an acceptable voltage sensitivity, you end up seeing the transformer in line too.
Then, if you make it a two way system with a crossover, then you have two such systems and the effects of the crossover etc.
Basically, it doesn't matter what the impedance is as long as it is higher than than the minimum load the amplifier will tolerate.
This can be more of an issue with ESS speakers because the capacitive reactive load draws the most current up high and the current phase angle leads the voltage, both of which are "different" than electrodynamic speakers and makes it a more difficult load.
An up side however is that the pressure produced is in phase with the voltage (unlike a direct radiator) and so the ESS, like a proper horn, can preserve the input waveshape, that is a square wave in produces a square wave coming out. For the most part, direct radiators do not preserve the input waveshape, they spread the signal out in time too much.
What matters too is that audio systems are a Voltage based reference and not a power based reference. Frequently you see people concerned with the impedance curve.
If the system is flat with a fixed voltage drive, then it is like the recording process where X pressure equals X voltage.
Best,
Tom
> > What matters too is that audio systems are a Voltage based reference and not a power based reference. Frequently you see people concerned with the impedance curve.
If the system is flat with a fixed voltage drive, then it is like the recording process where X pressure equals X voltage.Could you expand on this, where does impedance based dB attenuation figure. Not sure if you are covering a different point here but given ohms law it's trivial to demonstrate that a speaker with an significant input impedance variation would suffer from audible impedance induced attenuation if driven by amplifiers with reasonably high output impedance. For example the A3 impedance curve above would suggest that attenuation would occur in the bass and the critical 3-4kHz region with obliging amplifiers, or are you discussing a different issue?
Music making the painting, recording it the photograph
Edits: 05/10/09 05/10/09
Both designs referenced employ dual transformers which are frequency specific, but sum their output to the full range panel or panels in the case of Acoustats. Indeed their load is challenging. The amp I used with my first stats back in the early 80s was a Threshold Stasis that was designed specifically to drive Dayton-Wrights. I currently use a pair of VTL tube amps which seem to be a better match.
...they spread the signal out in time too much.
Perhaps that is why I favor the imaging of my stats to most direct radiator type speakers.
rw
Hi
Yeah, the best sounding amp i had for the ESS speakers was a pair of hot rodded tube mac mc60's.
They were better than any of the SS amps i had on the Accustats, Janzen panels or the home made ones.
I had a Threshold Stasis II later but by then I was pondering horn systems.
Best,
Tom
work exceptionally well with the Sound Labs. Wish I had the Siegfrieds. :)
rwr
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