The Sanders Magtech amp is designed to play electrostatics. Not inexpensive, but should be mentioned to make this thread more complete. A friend uses a 200 watt per channel Classe to drive Martin Logan CLS. I use Acoustat Model 3 ( full range) with Hafler DH 500 modified by Musical Concepts. 

Acoustat speakers seem to be very reliable. Perhaps the most reliable stats made. But, every product breaks once in a while. 

Enjoy the stats,

aldnorab

Thank you all for your responses.  I would especially like to thank Atmasphere 

for such a great explanation and Charles1dad for his experience with the VAC

70/70 and Acoustats.  

If I wasn't on a budget I would buy the Atmosphere M-60.

All the best

I'm going to move a tube amp into my second system room where I have some mature Martin Logan CLSs and see how it goes.  I hadn't really tried it before.

@carlsbad If you have CLS 1s you can do this easily. Any later version of the CLS is much lower impedance, so if you want to use a tube amp with them you'll need a set of ZEROs (www/zeroimpedance.com) otherwise you'll have no highs.

I had Accoustats...started on fire.....glad I was home to put it out

@stratmosphere I'm going to move a tube amp into my second system room where I have some mature Martin Logan CLSs and see how it goes.  I hadn't really tried it before.

@atmasphere 

Put another way, many tube amps could probably play this speaker.

I’m glad you took the time to reply and explain on this thread. I wasn’t aware of the detail and insight you provided.  However, I know what I heard on numerous occasions with the Acoustat speakers and VAC Renaissance amplifier combination. Again, truly wonderful sounding music presentation.

Thanks to your explanation I have a better understanding of what I clearly heard. The comments regarding sensitivity measurements vs real world performance, makes sense. The room was spacious yet this pairing had no difficulty filling it with music.

Charles

@fortepiano50 , @charles1dad There are certain Acoustats that IME are very easy to drive.

First let's debunk the sensitivity thing. While rated at 81 dB, keep in mind this is at 1 meter. This means that the efficiency of the speaker is actually higher, since its a panel and a lot of its output will not be picked up by a microphone placed only a meter away. Typically add 6dB for a more realistic figure.  You will experience as much sound pressure at 10 feet away from the driver as you will at one foot.

The other issue is impedance. ESLs have an impedance curve that varies by about 9 or 10:1 from the peak impedance in the bass to the impedance at 20KHz. Therefore the frequency of the sensitivity measurement can have a big effect on the reading you get, since that can vary the result by + or - 3-6dB- the speaker is higher efficiency if the impedance was more than 8 Ohms at the frequency of measurement; less if the impedance was less than 8 Ohms.

In practice customers of ours used our M-60 amplifier to drive Acoustats with good results in fairly large listening rooms. So I suspect that they are really in the 91dB region, much like other ESLs once you winnow these things out.

With some of those Acoustats, to get the M-60s to play properly we had to use a set of ZEROs so they wouldn't sound rolled off in the extreme top end. But some of the Acoustats sounded fine without that, which suggest that their impedance was fairly high. This would account for why some solid state amps wouldn't drive them all that well, since the higher impedance would have reduced their power output. Most solid state amps will cut power in half with each doubling of the impedance.

So if our M-60 could drive the speaker that suggests an impedance curve similar to a Quad ESL57 or ESL63 - about 45 Ohms in the bass. A 100 Watt solid state amp would only make about 17-18 Watts on such a load where our OTL would make full power. 

Put another way, many tube amps could probably play this speaker.

I had 2+2s for a couple years with the interfaces with Medallion transformers. Over time I acquired their servo amps, which sounded amazing, but in those days (1996) the amps were very unstable. There is a guy in Florida I think, who repairs/rebuilds them. Worth finding him

hth

@charles1dad 

Great. I am just relating my experience. I run all tubes these days… left electrostatics and other planar in the past.

This is exactly what that Acoustat dealer had.

@ghdprentice

That is really interesting. As I mentioned above, the local Acoustat dealer (Early 1990s era) drove his speakers with the VAC REN 70/70. And believe me, that pairing absolutely sang beautifully. In addition he had a decent size listening space. Admittedly Kevin Hayes built those particular amplifiers with major quality output transformers and power supplies. That VAC model weigh nearly 100 pounds.

Charles

Charles

Back when you could buy them new I auditioned a pair of Acoustat 2 + 2, they required massive current. I got bigger amp: they drained the massive 75 pound Yamaha… 150wpc (?) I tried. Drained it dry at relative low volume. I had to return them. I bought the biggest newest Threshold s500 to power them… but it was so expensive I couldn’t afford to buy the Acoustat.

Perhaps, someone has more recent experience… but I would look at a Pass 350.

Thank you all for the suggestions.  I have also started looking in the older forums and this situation has come up a number of times.

All the best to you and your families!

@jasonbourne52 +1

Sorry, forgot to mention, he also had a pair of subwoofers along side of his acoustats. I must say I was very impressed with the sound I heard, considering the age of the speakers. He also had mentioned that he thought they were 82 or 86db efficient .

Sorry, forgot to mention, he also had a pair of subwoofers along side of his acoustats. I must say I was very impressed with the sound I heard, considering the age of the speakers. He also had mentioned that he thought they were 82 or 86db efficient .

Back in the day there was an Acoustat dealer that I visited on several occasions. He drove the speakers with the VAC Renaissance 70/70 amplifier (Push-pull 300b, 65-70 per channel) with truly excellent results. Granted these amplifiers were built with very stout power supplies ​​​​​​.

I did not realize that their sensitivity was that low (81db) so I understand The recommendation for higher power solid-state amplifier. But, I can attest to the fact that they were marvelous sounding driven by the VAC amplifiers. The speaker probably has a friendly impedance load.

Charles

It depends on you room size. Just yesterday I went over to my buddy's place. My buddy had my LSA wasp class D ...125 wpm into 8 ohm amp at his place for 2 weeks. . He has the acoustat, not sure of model, about 7 feet tall and maybe 12 to 15 inches wide. His room is approximately 17 ft by 21 feet. He had been using NAT mono blocks, but couldn't get them to drive the acoustats. His jaw dropped when he heard this amp with his speakers. he subsequently, spent many hours in the music room. I can only guess that the current the amp produced is what drove them satisfactorily.

Forget about any amp less than 200wpc. With a sensitivity of around 81db/meter the 1+1's need a lot of watts to come alive. My Perreaux 2150B with its 920wpc@2ohms would be a good match. Another good amp would be the Acoustat TNT - designed by Jim Strickland to work well with his speakers.

The acoustats will sound best with tubes that can deliver a good amount of current. That said I’d also pick an EL34 amp over a KT88 amp for electrostats given the sonic signature and midrange magic. Unfortunately EL34 are lower powered, so if you have a larger room you will benefit from EL34 monoblocks. Or an integrated or separate amp using at 4-8 EL34 tubes (4 should be fine for a small/mid room, 8 will be needed for a larger room).

I’ve heard the Pass 150 and I wouldn’t pair it with the acoustats as it has a less warm, and thinner character compared to much of Pass’ other offerings.