Sanders 10B Electrostatic

Albert, I hope member Cerrot will chime in. He owns the latest rev of Sanders' speakers - the ones w/ the aluminum woofer; i *think* it's the 10D but I'm not sure.
If you look at his system, he's using Sanders' Magtech amps as well.

The electrostatic speaker can be modeled electrically as a huge capacitor which means that it's output impedance is high at low frequencies & low at high frequencies. Just the opposite of any conventional box speaker. So, the amp has to be designed to output sufficient current to drive into a higher load impedance at low frequencies otherwise the bass response will suffer. I believe that Sanders' ESL & Magtech amps are designed to this. There must be other amps in the market that are also designed to drive an ESL but none of them come to mind.
The Wolcotts are not an option any more, I believe, as they are out-of-biz (?).
Maybe Tube Research Labs (TRL)? I know an acquaintance who has successfully used them on his Apogee speakers but the Apogee is a planar magnetic speaker; quite different from an ESL.

8-31-15: Albertporter
Clio09
Albert, it may not be required for the 10B but how many 100 watt tube amps can drive a 1 ohm load?

Is the Sanders a 1 ohm load? If yes, do you know across what part of the musical spectrum?

What is your opinion on 200 + WPC tube amps? Say Audio Research REF 250W mono blocks or Atma-Sphere 200W mono blocks?

Do you think they are up to task for Sanders?

Albert, I wrote this before but I don't think anyone read it OR if people read it, they didn't understand. So, I'm writing this again:
as far as the power amp is concerned, these ESLs can be modeled as a huge capacitor. This means that at low freq, the load impedance is high. At high freq, the load imp is low. Plus, for a capacitor the current leads the voltage by 90 degrees. This means that current & voltage are not always provided to the speaker at the same time (unlike conventional box speakers or even planar magnetic speakers). This means that the amp can potentially go unstable. How many times have you heard & read that the power amp failed into a high capacitance load? We've even read this for high capacitance speaker cables (like Alpha Goertz).
The other thing to note (since these ESLs behave like capacitors) is that these speakers are voltage driven devices (rather than current driven devices like conventional box speakers & planar magnetic speakers). So, the power amp needs to have a very high DC power rail. It's no surprise that both Sanders' amps are 400W/8 Ohms & 500W/8 Ohms where the DC power rails are +/-80VDC & +/-90VDC. And, they also provide a gobs of current.
What's happening here is that as the speaker impedance increases at lower freq, any amp would be pushing current into this higher load impedance & the output voltage will rise quickly. If the DC power rail of the power amp is not high, the output voltage will clip & you'll get distortion. A high DC power rail (such a 80VDC or 90VDC) will tend of avoid this output voltage clipping.
You were suggesting an ARC REF 250. If this is a 250W/ch, 8 ohms, I calculate the DC rail voltage to be 63VDC. That seems reasonable but I surmise that the output voltage might get close to clipping if the volume is turned up. It's hard to say; best to get a home/dealer audition with these amps.
Just a quick calculation: usually the first watt is where most of us listen but I don't know how loud your friend likes to play his music.
Suppose that he cranks up the volume such that the amp is outputting 5W into the speaker. If the speaker presents a load of approx 800 Ohms anywhere in the 200Hz-20KHz region (the bass is taken care of by conventional woofer) then the output voltage will hit 63VDC & will clip. Will your friend crank it up to 5W output? Hard to say...
I would not go below 250W/ch 8 ohms & try to look for something even higher in wattage (just to get that higher DC power rail voltage).
Hope this helps.
Thanks.

On second thoughts: 800 Ohms impedance presented by the ESL seems to be rather on the high side. So, maybe the 250W/ch REF 250 will be fine with the Sanders speakers....
(like I wrote it was a quick back of the envelope calculation. ;-) )