PM Ralph Karsten (Atmasphere). He has posted numerous comments about Sanders ESLs.
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Hello Bifwynne, and thank you.
I did a search of Audiogon forums before posting my question. I will absolutely take Ralph’s recommendations to heart.
I would like input for as many brands as possible as well as power requirement. I have zero experience with this speaker other than listening to it at shows.
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.
I agree about Wolcott, I moved out of mine when service options dried up. They were good but other amps have come along since then.
A friend I spoke to today said there were tube amps designed for Sanders speakers. The brand is Western Reserve, I found a review at 6 moons but other than that I have not even heard of it.
Western Reserve appears to be stereo using four KT-88 per channel. I think a 250 to 400 watt designed for the new KT-150 would be another alternative.
Albert, I would suggest taking a look at the Music Reference RM-200. Can drive a 1 ohm load and Roger Modjeski has plenty of experience with ESLs having worked for Beveridge, designing the RM-10 for the Quad ESL-57, and now having his own ESL system, including the ability to build a direct drive amp for ESLs. I have been helping him set up his new shop in Berkeley so while he is busy I am sure he'd be happy to provide some assistance.
Wow, is that required for the Sanders 10B?
I've spoken to Roger at shows many times, definitely a passionate man about his speakers and they do indeed sound good even under show conditions.
My fear about asking advice on amps would be some bias toward his solid state design.
My friend is searching for tube amp option so I‘m hoping for real world experience from Audiogon members. I appreciate all the input so far, wish I had experience with these so this would not be necessary.
Albert, it may not be required for the 10B but how many 100 watt tube amps can drive a 1 ohm load? Given that it should be able to handle the impedance of the speaker. As for current, if the RM-200 doesn't meet the challenge I am sure the RM-9 Special Edition can, but the price on that amp is substantially higher compared to the RM-200.
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?
Given what is written here: http://www.dagogo.com/sanders-sound-10b-floorstanding-speaker-review a pair of Atma-Sphere M-60's or the previously mentioned Music Reference amps should do the trick. If what I read in the review is correct the bass section of the 10B has it's own amp and electronic crossover. So the tube amp only has to power the panel section.
I heard the Sanders speaker at this years T.H.E. Show in Irvine, and I've been lusting for a pair ever since---I loved 'em! With Sanders, Ralph Karsten, and Roger Modjeski, you have three very good designers, each of whom will give you a different opinion on an amp suitable for driving them. Sanders can be ruled out for your friend Albert, as he's a SS man. Karsten will of course recommend one of his amps (nothing wrong with that!). As for Modjeski, in his Forum he wrote that the common wisdom of an OTL being a good match with electrostatic loudspeakers is, in actuality, incorrect. Roger has designed OTL's (a really good one manufactured and marketed by Counterpoint in the 80's), and will build you one now. However, he points out that the interaction of the impedance load of an ESL with the high output impedance of an OTL amp makes them very much incompatible. That the legendary pairing of the original Quad with a Futterman or NYAL amp produced wildly inaccurate frequency response, as well as ringing and instability in the amp. I'll bet one reason Sanders would recommend a SS amp is, for one thing, precisely because of their generally low output impedance.
8-31-15: AlbertporterAlbert, 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.