A finished ESL
Both Finished ESL's and the Velleman K4040 (center)
A newly assembled panel
I decided to have the ESL stators custom made rather than buy ready-made electrostatic speakers from companies such as Martin Logan. I bought the stators from Russ Knotts at http://www.justrealmusic.com and I designed and built the crossovers and with the help of a carpenter friend built the solid Mahogany frames and MDF bases. These stators are 15" X 48" and there are 2 of them stacked on each front channel. That gives a total of 1440 square inches of panel area per channel . When mounted the frames and bases are 100.5 inches tall. With 1440 square inches of panel space they should go down to about 80 Hz but with the current transformers I am using 200 Hz is about the best they will do. I may try some better transformers later. They are 90:1 ratio. The diaphragms are 0.005 thousands of an inch thick and the stators are 16 gauge (0.060") cold rolled steel that have been triple powder coated. ESL's don't have much vertical dispersion and having 2 panels stacked alleviates this problem and the sound doesn't change much if you are standing or sitting. I am currently testing the new panels and frames and doing lots of subjective listening. They are very articulate and detailed sounding and like most ESL's have a fairly narrow "sweet spot". I am crossing them over at 200 Hz to the subs right now but am building new midbass towers that will work from 200 Hz to 60 Hz. I did have them crossed at 160 Hz and found that at 200 Hz I get about 2 dB more output from them. I am very happy with the sound so far. They are reasonably efficient and play loud enough to satisfy most people. They play about 3 dB louder stacked. I can get about 106 dB max from them stacked depending on the music. I was using a Carver TFM55x power amp and just purchased a current model Velleman K4040 90 watt per channel tube amp that replaces the Carver.
Update - I have been listening to the Velleman Tube/Valve amp and so far have mixed feelings about it. I have owned many tube amps and ESL's before and usually a tube amp sounds "sweeter" and more open than most solid state amps. I was surprised when I noticed that the Velleman (I brand I have never owned before) seems to sound more like a solid state amp. I don't know if its a characteristic sound of this model or if its just not a good match with my ESL's. I will do some more experimenting such as different output tube brands etc. (it has Sovtek now).