Poll

Direct Drive ESL Amplifiers for all

I have ESLs and I would like to explore direct drive
10 (16.9%)
I can do basic re-wiring myself
11 (18.6%)
I need a technician to adapt my speakers
2 (3.4%)
I want to send my speakers for Roger to do it
1 (1.7%)
I want to make my own ESLs
6 (10.2%)
I have made ESLs and need a good way to drive them
1 (1.7%)
I find ESLs fascinating and want to know more about them
15 (25.4%)
I have read DIY articles and toyed with the idea of making some
6 (10.2%)
I think a DIY ESL can achieve excellent sound and is a rewarding project
6 (10.2%)
I have read DIY articles and find them confusing or unclear as to what to do
1 (1.7%)
The drive systems seem poorly conceived in the DYI articles
0 (0%)

Total Members Voted: 26

ESL Independence Day

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Roger A. Modjeski

Re: ESL Independence Day
« Reply #40 on: 11 Jul 2012, 04:07 am »
Would someone knowlegeable about that acoustat deal PM me and tell me why this is a good deal? I was just looking at Magnepans... so not sure what these are. (--planar Newb) I live near them.

Magnepans attempt to do what ESLs do but with a diaphragm that is 10 times more massive in a non-linear magnetic field. Their one virtue is that they are planar and that is all they share with ESLs.

Russell Dawkins

Re: ESL Independence Day
« Reply #41 on: 11 Jul 2012, 07:15 am »
:o
Wow, what a deal this was in Canada last April. A free pair of Acoustat X's and DD amps if you picked them up at his place.

http://www.canuckaudiomart.com/details/648994386-acoustat_x_speakers_servocharge_amps_conradjohnson_preamp/

Ouch, I am in the same city but never follow Canuck Audio Mart.  :roll:

steve f

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Re: ESL Independence Day
« Reply #42 on: 11 Jul 2012, 04:03 pm »
Traderxfan,
Roger gave a great explanation of the differences between ESL, and Magnepans. If you get the chance to listen to both, you will notice that ESL's do not ring, overshoots, or exhibit any tonal imbalances. Magnepans are driven from one side only so that there is kind of a "snap-blur" effect. The diaphragm has to restore itself after the signal drive. I would love to see some 'scope pictures comparing them reproducing sine waves.
Steve

TRADERXFAN

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Re: ESL Independence Day
« Reply #43 on: 11 Jul 2012, 07:55 pm »
Thanks for  the comments above, and OzarkTom's who pm'd.

 I wasn't so much weighing the pros and cons of magnepan vs acoustats. I just didn't have a clue about Acoustats.  And more specifically, what made this deal so special, since it is in my backyard.  I was skeptical because it seemed just to be old and defunct technology.

After doing some Google research about Acoustats. I read about some of the tradeoffs. The only one of which that gives me pause is a few comments mention rolled off treble.  Is that your experience?

I was expecting the complete opposite for the treble. I have a few different speakers here. The one that I have that most closely might give me an approximation to the design aspects of this would be my GR Research OB-7, paired with four 12" ob servo sub drivers.   The relatively extended highs form the B&G neo3  tweeters are one of the strengths I was looking for when I started thinking about a full planar speaker. 

But in regards to the line source aspect, and the crossover-less design, I have no approximation or experience with that.

-Tony

bpape

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Re: ESL Independence Day
« Reply #44 on: 11 Jul 2012, 09:06 pm »
Any rolloff is in the extreme high end.  They are very particular about listening height though.  If you stand up, yes, you lose the highs somewhat.  The Monitor IV's have an adjustment on the rear so the entire panel can be tipped back slightly to help avoid this problem and dial it in to your preference. 

The stock DD amps are head and shoulders above the transformers. I had mine completely rebuilt and some pretty serious mods done to them which really take them to a whole different level.

Bryan

OzarkTom

Re: ESL Independence Day
« Reply #45 on: 11 Jul 2012, 10:21 pm »
The Acoustats with transformers had the worst roll-off in the top in. I loved the top end with DD amps. I have never heard GR OB-7, only the GR Super V's. If you like that top end, you will like Acoustats top end. IMO, all ribbon tweeters have always sounded to hot for me.

But like Byan said, stay seated to get the best results. This is not a dance speaker.

OzarkTom

Re: ESL Independence Day
« Reply #46 on: 11 Jul 2012, 10:34 pm »
You might email that seller, TRADERXFAN, and he might will let you come over and listen before the auction ends. But the amps will sound much more open and clearer if they are modified.


steve f

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Re: ESL Independence Day
« Reply #47 on: 12 Jul 2012, 11:17 pm »
I didn't want to start another topic but I have a comment and also a question.

Earlier Roger (When I wrote that a buddy felt direct drive tube amps were inferior to solid state amps powering ESL amps through transformers) commented that the condition of direct drive amps not working well would be if they were ill-conceived DIY units. That is exactly the case. Martin Logan statements driven by Bryston amps verses a homebuilt DD tube amp driving Acoustat 1+1's converted to direct drive. Not a fair comparison at all.

My question to the group is since we are talking dipole speakers, how about Heil drivers? Not the offshore tweeters but the rereleased Great Heils.  I just finished restoring an original pair from old ESS AMT-1's. Combined with a decent corner horn, I am impressed. What is your experience with these drivers? Of course compared to ESL's.

Steve

OzarkTom

Re: ESL Independence Day
« Reply #48 on: 13 Jul 2012, 02:34 am »
I always tried to like the ESS's when first they came out, but the highs were just too bright. I also thought the bass was too boomy. When I visited the Heil room at RMAF last October, I just barely went into the room and quickly out. The brightness almost fried my ears and gave me a headache. But maybe there is an amp today that can tame that down.

I had a friend that used highly modified Heil tweeters in his system, almost sounding smooth.

steve f

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Re: ESL Independence Day
« Reply #49 on: 13 Jul 2012, 09:24 am »
The bass in the original was boomy.  I only kept the Heil cores, and cleaned them up, put in new diaphragms. I don't feel they are too bright. Perhaps amp choice makes a difference. Or maybe they are driving the tweeter several DB louder than the woofer. In my live hardwood floor room they sound okay.

airhead

Re: ESL Independence Day
« Reply #50 on: 13 Jul 2012, 04:00 pm »
I sold Acoustat and NYAL back in the 80's. I received a pair of the Acoustat Minitors with DD amps on trade. It was a night and day difference between the DD amps and the NYAL 3's, no contest. The DD amps blew the Futterman's away.

A further bit of information on the Acoustat + Futterman combination, the following quote from Harvey Rosenberg:

"On the other hand musicmaniacs would here these amps on Quad 63s and then used them on their Acoustat Monitors, where were very inefficient, 2 ohm speakers…which I advised against…and then I would get a call from and OTL-3 owner complaining that after only two months his amplifiers sounded distorted. As I suspected the output tubes were exhausted, and for good reason.The rumors started by the mealy minded that the Futterman amplifiers were unreliable arose because these thermionic feeble never understood that OTL amplifiers can only be used with a very limited range of loudspeakers…and be reliable."

The link is here…  http://www.meta-gizmo.net/tri/nyal/nyal_art.html

I should add that my OTL 3's have been very reliable with long tube life, except for the time one of the caught fire....


Roger A. Modjeski

Re: ESL Independence Day
« Reply #51 on: 15 Jul 2012, 12:04 am »
One must remember that OTL amps like the Futterman and Atmasphere are current limited and thus put out decreasing power into lower loads. In approximate numbers you can get 1 to 1.5 amps per pair of tubes so 3 pairs in the OTL-3 would do 3 to 4.5 amps, about right for 100 watts into 8 ohms. Divide that in half for 4 ohms and half again for 2 ohms. As to burning up the tubes, that is correct because the voltage that is not appearing across the load is not across the tubes thus taking their dissipation far beyond rating.

It should also be noted that in some ESL step-up transformers half the total capacitance is in the transformer itself. Direct drive removes this undesirable load. The Quads work out to about 200 pf with my crossover which is quite easy to drive at high frequencies. Acoustat panels are about 300 pf each. In the larger speakers this does add up but I make a higher current amp for those. The big one I am making for a customer drives 8 panels that's 2400 pf. We made some measurements and found that with that much area, even in a very large room, half the original Acoustat voltage was plenty for extreme levels. Therefore I made a lower voltage, higher idle current (more class A) amp for him.


OzarkTom

Re: ESL Independence Day
« Reply #52 on: 16 Jul 2012, 12:05 pm »
Those Acoustat X's on Ebay went for $910. Did anyoe here get those?

And here is a pair of Acoustats in Ramona Ca. for $500. These even have the original boxes and owner's manual.

http://sandiego.craigslist.org/csd/ele/3134944198.html

Atom666

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Re: ESL Independence Day
« Reply #53 on: 19 Jul 2012, 02:30 pm »
Hi
 I just came upon his thread. I would be very interested in seeing the schematics from Roger. I am in the middle of rebuilding some Acoustat Monitor 4 using 4  x  9" panels /channel. I have a MK-121 interface to drive them but would be very interested in direct drive amplifiers for them. There was also a circuit designed by Alan Kimmell for direct driving electrostatic speakers it has 8  x  6HV5 tubes /channel and was offered by David Lucas at one time  but I have never seen any more info on the net about the amps.
Andrew

Roger A. Modjeski

Re: ESL Independence Day
« Reply #54 on: 21 Jul 2012, 08:36 pm »
Hi
 I just came upon his thread. I would be very interested in seeing the schematics from Roger. I am in the middle of rebuilding some Acoustat Monitor 4 using 4  x  9" panels /channel. I have a MK-121 interface to drive them but would be very interested in direct drive amplifiers for them. There was also a circuit designed by Alan Kimmell for direct driving electrostatic speakers it has 8  x  6HV5 tubes /channel and was offered by David Lucas at one time  but I have never seen any more info on the net about the amps.
Andrew

Does anyone know where David Lucas is? I had a bad experience with him and I hear others did also.

I would be interested in seeing the 6HV5 design,though I wouldn't use that tube. It was designed to be a pulse type shunt regulator in a color TV and it's linearity is not so good. From a reliability point of view its better to have a plate cap for the high voltage, which the 6HV5 doesn't.


neobop

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Re: ESL Independence Day
« Reply #55 on: 23 Jul 2012, 12:44 pm »
Roger,
A fellow named Dan Fanny, formerly of American Hybrid Technology in Trenton NJ, rebuilt Acoustat DD amps.  He had boards made of his design. He used cap tubes which were an upgrade from horizontal stabilizer? (prob 6HV5) TV tubes.  I believe the only thing original was the power transformer and any storage cap that was still good.  I had a pr of these amps, they were astounding.  He used all different kinds of high voltage storage caps. I remember stringing together banks of 250V photo-flash caps to make 50KV with relatively high current. They packed a wallop.

Danny had 2 +2 panels, The sound was effortless.  I'm not sure how many sets of these amps are floating around, they didn't all have photo-flash caps, but I think they would be worth checking out. The tubes last quite a long time.  When you wrote about biasing tubes, you reminded me of Danny.  He told me that when it comes to biasing and matching, nobody knew what they were doing. The tubes in my conventional 50 wpc amp, were good for around 10 yrs.

steve f

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Re: ESL Independence Day
« Reply #56 on: 29 Jul 2012, 02:06 pm »
Question for Roger.
How are the direct drive ESL amps coming along? Anything new to discuss?

steve f

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Re: ESL Independence Day
« Reply #57 on: 3 Sep 2012, 01:51 pm »
Bump

Baranyi

Re: ESL Independence Day
« Reply #58 on: 6 Sep 2012, 04:22 am »
A friend of mine in Maine has a pair of Acoustat 3's for $450! He has them listed at Boston Craigslist. At my urging he picked up today a pair of Monitor 4's in their original boxes for $500!

OzarkTom

Re: ESL Independence Day
« Reply #59 on: 6 Sep 2012, 06:43 am »
A friend of mine in Maine has a pair of Acoustat 3's for $450! He has them listed at Boston Craigslist. At my urging he picked up today a pair of Monitor 4's in their original boxes for $500!

 :o

With the servo amps?