Need Help with Acoustat Model 4 speakers

I bought these Model 4 speakers with the Mk 121 interfaces on a whim. They aparently are in need of service as they play very softly, with the receiver volume needing to be cranked up just to hear them. Would appreciate any thoughts on these, really regret the purchase at this point.
Very few receivers have the current to drive Acoustat or any other planar for that matter. These require a least 100 WRMS perside in power with at least 20 amp in current delivery. Ideally you should be into a separate power amp and preamp to get the most from these speakers. Accoustats have a widely varying ohm load and can dip into the 1 ohm range depending on source material. The new batch of receivers on the market today just cannot handle that kind of ohm load, a few receivers back in thelate 70's and early 80's were capable such as a Luxman 1070 for instance, but nothing in the current line up of modern receivers can be expected to drive the Accoustats.

Accoustat are some of the most difficult to drive planar speakers ever made. Over the years have had several of the pass through here. With these model 4 I would use a 200 WRMS per channel amp to derive the most from them. Even with a proper amp they will not be able to be driven to ear splitting levels. I have found that Accoustat works the best with Jazz and Classical music as well as vocals.

They are a great speakers, just not for everyone.
What receiver are you using? The biggest bang for the buck is Acoustats own amplifier called the TNT-200.
Here's a really dumb question - have you plugged them in? I don't know if they would even work if you didn't. I've never tried.

FWIW, my 2200's really needed a high current 200/400 SS amp to get them off the ground. I've never had the 4's but I believe Ferrari's comments.

BTW, lest you happen upon and want to buy an Acoustat Amp, don't assume that it will be ideal as suggested. One of the initial reviews of this amp commented on its current delivery and thought it was interesting that indeed it was not ideal for at least some Acoustat speakers. I think the speakers were the tall two's but my memory is poor for that kind of detail. Oh, more trivia. As I recall the design for the Acoustat amp was passed on to and used in one of the later Hafler amps. I think the designers name was Strickland. FWIW.
Newbee, The Acoustat TNT-200 was designed by Acoustat to drive Acoustat speakers. I could not say it is the best amp to drive Acoustats, but I can tell you it out performed my Levinson 23 while driving Acoustats of the same vintage as the OP's Acoustat 4's.

Your comment of your Spectra 2200 needing 200/400 watts to get them off the ground is misleading since Acoustat speakers reach a volume threshold and in reality a good 100 watt tube amplifier would be adequate. Your Spectra 2200 which is half of the OP's speaker most likely would not be able to handle all the TNT-200 has to offer.

After Acoustat was sold Jim Strickland stayed on with Hafler and Rockford Fosgate, which were subsidiaries and his TNT (Trans Nova Twin) amplifier design was pass down to Hafler to rekindle that brand in the marketplace, which it did for a while.

This post is a good example of why Acoustat designed the TNT-200. It was an incrdible bargain when it was new and it's an even better bargain now on the used market.

Rrog, FWIW my post was cautionary and not meant to be more than that. I could elaborate on, and discuss with you, my experience with both the 2200's and the TNT 200 but I won't as it serves no purpose on this thread.
Newbee, On the contrary, your experience is invaluable to the OP and anyone else thinking of buying vintage electrstatic speakers.
I have owned 3 pairs of Acoustat 3's, one pair of 4's, 2 pairs of Model 33's, one pair of Model 3300's. The Acoustats were a 4 ohm speaker that would dip to 2ohms around 14k hertz. No problem. If unplugged, of course there will be no sound output. If unplugged for a few days, they need to be powered on (capacitors charged) at least one full day before they reach their sonic potential (good sound). Of course they will play after charging one hour, just don't expect great sound. I drive them with PASS Labs X250.5 amp (250wpc 8 ohms, 500wpc 4 ohms.
I drive a completely refurbished pair of Spectra 44 with a Coda 100 watts class A amp. High current at 50 A up to peaks of 100 A.

All the electronics are new with V caps, caddock resistors and the rest. The panels have been soaked to remove all particles accumulated over the years.

And they play beautifully, lots of impact at medium level. So the most evident question is : are your interfaces and panels top notch in full potential condition ?
Skykomish, I used to own Model 3's with the 121 c interfaces. As others have said, the speakers need to be plugged in all the time. Acoustats are fairly difficult to drive, although a 50watt tube amp should do the trick. One other thing about these speakers is that they could be damaged by arcing, like most stats. I had a friend with 4's who managed to arc them severely and that was as they say that..:0(
After about ten years with the 3's, I gave up on them and now I never look back.
I just bought a pair of Model 1 +1 with the Hafler Medallion 141C transformers. Like the OP, I could only get faint volume out of 'em, even with a very good 150w amp. (I did plug them in). I opened the transformers up, and the fuses all appeared intact. The guy I bought 'em from, who appears honorable, claims they worked perfectly, but hadn't been used for several months. Being largely moronic about electronics, could it be something as basic as the capacitators needing charging? Your help is most appreciated.
Clueless in Chicago
It could easily be that the capacitors need to be replaced.