Stacked pair of Quad ESL 57

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We (Guido Tent, Rob Humbertse and Arend-Jan Wijtzes) teamed up again and wanted to do something interesting for the 2011 European Triode Festival (ETF) with the main theme 'Vintage Audio'. So I suggested to provide a stacked pair of Quad ESL 57 electrostatic speakers. Rob Hubertse provided a tube pre-amp and a streaming audio setup. Guido Tent provided a Tentlabs CD player and his latest generation class D amps. Peter van de Willenswaard brought a system with modified Audio Note AN-e's and his 300B single ended amplifiers.

The first evening we played on the Audio Note's and single ended 300B amps (which is a very very nice system indeed!) while we build up the frames for the Quad stack. The speakers were given ample time to charge overnight. The next day we started our first experiments with the stacked pair. Running them in parallel on the 300B SE proved to be not such a great idea. The amp was clearly running out of breath.

Next was to hook up Guido Tent's b-Amps. Two mono blocks of high quality class-D (modified Hypex modules) with plenty of power. Boy did those speakers come to life! We were stunned by the gain in bass, power, dynamics and authority over a single pair. At some point we were running streaming audio and because of the difference between recording levels, we were presented with a drum solo/intro at ear splitting levels. But it still sounded clean!

During the day we tuned the sound by adding a series resistor of 1 Ohm at the output of the amps. This rolled off the highs a bit and made the stack sound more natural.

Later we tried to run them again on the 300B with the 4Ohm tap but quickly reverted to the Tentlabs amps. Perhaps we should have tried with the speakers in series instead of parallel but our speaker cables did not allow to do this easily.

The Quads
I did a full refurbishment of the Quad ESL speakers and made some small modifications to the bass panels and crossover to accommodate for the increase in size and the fact that we were running them without covers.

Listening experiences
We had three days to evaluate the stacked Quads. My first impression was a gain in power and dynamics but a loss in focus and soundstage. After tuning the setup the soundstage was regained in the sweet spot, although perhaps not as pin point as a single pair. More experiments are required here but the gain in presence, bass, authority and dynamics I would happily trade for a small reduction in pin point imaging if that would be the case. Also the speakers were much more enjoyable outside of the sweet spot than a single pair.

All in all it was truly stunning to listen to Quad ESL's reproducing the latest album of Yello at 95dB without distortion. Never imagined they could do that!

Stacked Quads charging in a corner:
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Stack being build:
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:D
 
Lovely!

I ran a stacked pair, in stands as per Peter Walkers design, about 17 years ago now.
Each was driven by its own amplifier (QUADII) but I never did get the soundstaging focus and intimacy of a single pair, despite a year of tweaking placement, and working with different angles and focus points of the speakers in each frame....

Possibly I needed to sit farther back from them to allow better integration between the two speakers in each stack...i.e a bigger room!

Like you I experienced the greater dynamic range and loudness capability but IMO it never really compensated for the loss over what a single pair could do!

Great to see folks still stacking em!

Ta

WM
 
Lovely!

I ran a stacked pair, in stands as per Peter Walkers design, about 17 years ago now.
Each was driven by its own amplifier (QUADII) but I never did get the soundstaging focus and intimacy of a single pair, despite a year of tweaking placement, and working with different angles and focus points of the speakers in each frame....

Possibly I needed to sit farther back from them to allow better integration between the two speakers in each stack...i.e a bigger room!

Like you I experienced the greater dynamic range and loudness capability but IMO it never really compensated for the loss over what a single pair could do!

Great to see folks still stacking em!

Ta

WM

Thanks for your feedback. Indeed, as far as I can tell you need a big room to run them stacked. The room was approximately 120m2 or more, pretty big. I found out the hard way two years earlier that a single pair drowned in that exact same room. No fun to listen to at all :(

@tyu
About the Krell, I agree a good big amplifier will make them come alive. And it has to be quality material. I've listened to single pairs for 7 years now on different tube amplifiers, the best being a single ended GM70 producing about 35-40W, followed by a 20W 300B push-pull amplifier. But recently I'm starting to discover that even more power is better. Just get those protection boards installed first!
 
Thanks for your feedback. Indeed, as far as I can tell you need a big room to run them stacked. The room was approximately 120m2 or more, pretty big. I found out the hard way two years earlier that a single pair drowned in that exact same room. No fun to listen to at all :(

I know that many have been enthralled with stacked pairs so I think its a goal worthy of pursuit but yes I think one has to sit quite far from them to get good integration and averaging between the two speakers - and in my case my room would just not allow it. :-(

I pushed them further back but then they became too close to the rear wall and thats a no no as well.

But either way stacked or single they are very special speakers and at least one pair have always been in my home since I could afford them....

Lovely stands and beautiful recondition of the ESLs?

Thanks

WM
 
I have toyed with this idea many years and never did this based on the resulting image issues, but the central ribbon or even a 3/4" ceramic coated dome idea should result in a better focused image.
Hooking one up with a simple 6th cap and L pad would prove interesting.
One thing about the quads that make them special is the incredible downward dynamic range that eclipses most other electrostatics. While they have limited overall dynamics they make up for it going the other direction.
That stack must surely cure any issues on dynamics!
Did you series or parallel these?

Regards
David
 
The Quads were run in parallel. We should have tried series connection (on the 300B) but didn't.

I think the sounds stage issue is a matter of setup and distance to the speakers. If you have enough distance then, theoretically, there should not be too much difference between a single pair and a double pair. Unfortunately we had a busy program and lots of people wanted to audition the stacked Quads, so once they were set up there was little time to play around and experiment.

At my place I don't have the space to put them up. I'm going to do a series of measurements on a mono stack and probably sell the frames after that.
 
I've been browsing where I normally don't and came across this thread and thought a zombie post was in order.

I've been running stacked quads for a while now, powered from a rebuilt ST70 with KT66s. My room is nowhere near as big as the one shown, and I tend to sit fairly close to the panels. I have found that positioning is very important - an inch or 2 is all it takes to throw it off. Probably more fussy than a single set.

I use a nordost set up disc that I picked up at a show. It has a useful set of tones that pan up and across the stereo image - they are very useful for working out distance and toe in. The other thing that I think is very important is the rake - I have found that having the panels dead vertical sounds best - I've tried everything from the "standard" angle to "falling forward" and vertical works very well for my room at least. This can be awkward to try out, but its worth it.

One of my sets is from 1974 (never serviced afaik) and the other set are very early, from 1959, serviced by quad in 1981. I know they are probably not at their best now but can't bring myself to tear them down to service them! Foolish maybe...

Arend-jan - what was the chipamp you mentioned in the post? I tried running them from an F5 but that combination didn't err, get on. Burn out resistors in the F5!

Fran
 
Hi Fran,

I've been thinking about this and I think set-up becomes more difficult when you are in a smaller room and close to the speakers. It was not as critical as I expected it to be in this large room. In fact it was easier than a single pair in a small room. But I must admit I did not fiddle with it endlessly to get the most out of them, when it was good enough it was good enough.

When you say having the panels dead vertical, do you mean you removed the panels from their original frames and mounted them flat in a custom frame?

The amplifier that we used was the Tentlabs b-amp that comes to the market this summer. Very nice indeed!
 
You might well be right on the setup in a smaller room. I also have an issue with so boominess in that room that was greatly reduced by the careful positioning. On the whole though, the stacked pair sound better than a single set.

No, I haven't removed the panels from the speaker, just that the whole speaker is vertical in the frame - and the frame is also vertical. I originally built my frames with a rake of about 10deg off vertical, but later experiments led me to change to vertical.

I haven't tried wiring them in series - must try that now, plus I must try my lm3875 chipamp too...

Fran
 
Fooling around stacked Quads from as way back as the 70's. Stacked quads need room, If you are using a small room , be prepared to treat the room Diffusers is a necessity . Here's a pic of a friends recent setup , the room is full of diffusers and it is actually a pretty big room..

Triple need seating position 18 ft away ... :)
 

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Seeing as we're sharing..... Here's a rather poor phone camera shot of mine.


I switched to series wiring today - and it's quite an improvement! I used the 16r taps on the st70, might go back now and give the F5 another run, and also the lm3875 chipamp too.


Fran
 

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