Stacked pair of Quad ESL 57
 

http://quadesl.nl/img/stack/etf11_st...uads_small.jpg

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:
http://quadesl.nl/img/stack/stack_charging_small.JPG

Stack being build:
http://quadesl.nl/img/stack/stack_build_small.JPG

:D

Awesome !!!!!!

I wish I could have been there to hear them !!!!

jer:)

Thanks for the pix...vary cool...i had a pr of stock 57s an found that a Krell KSA 250 sounded the best out of all the tubes an any other amp i put on them...

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

Hi Arend-Jan

Very, very nice set up. Thanks for sharing.

Wachara C.

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!

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 was there, heard them, and can confirm every word. the sound was really nice! imaging was not super-precise as mentioned above but it might have been caused by the source

great setup!

Here is a picture that gives an indication of the size of the listening space:
.
http://quadesl.nl/img/stacked-quads-1.jpg

Thank you - thats is a large room!

I would imagine that if you had time you may have been able to improve the focus/soundtsage by changing the inclinations of the speakers in each stand - but they look awesome and bring back good memories!

Ta

WM