Hi,
Well one of my single, and perhaps, the only advice is that you should take multiple tests before you build your final speakers. The use of smaller panels may not make integration easier, but maybe even more difficult. The reason is more restricted crossover ranges. I'm curious if you would succeed, because I have been disappointed by mixing ESL of different varieties and with dynamic woofers.
Regards,
Lukas.
Q: So with optimal polarizing and signal voltage the max SPL for a sine wave of frequency greater than 700 Hz is about 107 dB at 2 m. Is this a reasonable value?
A: It is a reasonably calculated value for 700Hz with the panel dimensions and measuring distance used. However since the panel will act like a line source at that listening distance, the response will slope off at higher as well as lower frequencies.
Q: For a frequency f below Fc the max SPL can be calculated as (assuming SPL drops 6 dB / octave):
spl(f) = SPL - log2(Fc / f) * 6 = 106.8 - log2(700.3 / f) * 6 dB
This value seem to be almost constant for a specific frequency regardless of the values of Fc or R. Is this a correct observation?
A: Yes. Max SPL at a given frequency is physical limit determined by panel area and break down voltage of air in the gap. It is not changed by putting a resistor in series with the stators.
Q: If you use DEQ to flatten the frequency response, what is the advantage of choosing a larger value for R (signal series resistance) and thus lower Fc?
A: The only advantage I could see is that the impedance would be an easier load for the amplifier with the resistance added.
Q: The capacitance between the stators is overestimated as they are perforated. Is there a better formula for calculating the capacitance if you know the perforation area percentage?
A: Actually, you will find that as long as your D/S spacing is at least as large as the diameter of the stator holes( or gaps between stator wires) the flat plate capacitance formula will get you within 10% of the actually capacitance. This is due to fringing around the holes and between wires.
Q: Also, why isn't the insulation or the coating of the stator included in the voltage breakdown calculation? Is it too thin to make a difference?
A: The impedance of the insulation is much lower than that of the air. So, the majority of the voltage applied to the panel winds up across the air gap rather than the insulation.
More details here:
http://www.diyaudio.com/forums/plan...truct-cube-louver-acoustat-7.html#post2154621
Q: Is there some free software that does all these calculations for you (and plot some nice frequency response graphs)?
A: diyAudio member arend-jan created a handy online calculator that uses a generalized form of the Walker equations.
Here is the site: Electrostatic Loudspeaker (ESL) Simulator
I previously posted some explanations for its use here:
Help with esl simulator Post #3
A later post in the same thread discuss adding resistance in series with the stators.
Help with esl simulator Post #7
Note that you will find listening distance relative to panel dimensions determines if the source is acting like a point source, line source, or plane source.
If the listening position is in the near-field relative to width & height, the response will be flat. (plane source ie headphones)
If the listening position is in the far-field relative to width & height, the response will rise at 6dB/oct (point source)
If the listening position is in the far-field relative to width but near field relative to the height, the response will rise at 3dB/oct (line source)
Some discussion on that topic along with a near-field breakpoint calculator here:
http://www.diyaudio.com/forums/plan...r-esl-simulator-esl_seg_ui-2.html#post2913884
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