My experiments with Quads

[xcortes]

A few months ago a friend sent a pic of a pair of speakers he was buying and I saw, on the back, a pair of Quad ESL 57s. I started enquiring and after a few negotiations I bartered them for a McIntosh preamp (that I had also acquired in an exchange) that was ready to be sold. They are in pretty decent cosmetic condition and in stunning operating condition.

The Quads are, to me, a magnificent example of industrial design from the late 50s. You could decorate a house around these (how about a second house, hmm, a beach house?).

They are famous for their transparency and midrange. Supposedly very picky about amplification with an impedance curve going down to 0.5 ohm that some solid state amps see as a short (with the following fireworks show) and that is not benign to SET amps. On the other hand if you feed them with more than 25 watts the internal panels arch and you can kill them.

I tried them with all types of the amps supposed to be good with them: solid state and push pull amps. They seemed to do some things very nice but with every try I would get tired quickily. Very fast and transparent but not musical. So I was about to call the experiment a failure, mark the "already tried" checkbox in my exotic audio list and put them for sale.

But yesterday I decided to try the no-no. I connected them to a pair of Paramours. I decided to give them a break for the first test so I rolled a tape of Cello Suites (JSB by Starker, just amazing) and voilá: magic. These speakers are magical. The mids are on par with those of my RCA drivers or Sony cans. That alone to me is very, very good.

So now I need to start looking for options. I’m pretty sure they won’t make it with more complicated material (but I could be wrong again). Thus I’m thinking of building a three way speaker system around them. My first idea would be to use them only from maybe 150hz to 5k (line level crossovers). Probably using three 300B amps in series as Doc does in his own midranges. An exotic tweeter (maybe an ionovac) on top with its own amp and something below (don’t know what yet) with its own amplification too.

That would relieve them from the nasties in the impedance .

Any thoughts?

[Doc B.]

Get a second pair and stack them. Gives you big bass. Also, they seem most happy with about 15 watts - maybe two Paramounts per channel, with secondaries wired in series.

[Paul Joppa]

Here's a quote I found:  "Quad II have a standard output resistance of 1 ohm when set with 16 ohm load matching on the output transformer, but this occurs at a limited frequency range at at high frequencies the output resistance rises enough to cause considerable attenuation at extreme high frequencies. ESL57 have a reputation for  being a bit "toppy" when used with a modern amp with low output impedance."

I conclude from this that a no-feedback SET, which has a few ohms output resistance which does NOT increase at high frequencies, might actually have a spectral balance that is pretty close to the original Quad II amplifier.

[xcortes]

Thanks Paul. That's exactly one of the things that bothered me (not the only one), too much highs. With the SETs the highs are perfectly balanced.

I continued my listening tests yesterday. I have to admit that 3.5 watts are on the low side for these speakers. They definitely need the 15 wtts of Doc's recommendation. Or 2x15 watts stacked.

My main conclusion remain: The midbass and mids are exceptional. The highs are very good but not the best (a little bit on the rough side). The bass is not good with the SET amps. Maybe with the bigger ones it will improve a bit but I wouldn't hold my breath.

On my research I've also found that my idea of using them as mids only with a line level crossover and separate tweeters and bass speakers has already been done. Mark Levinson designed such a system with stacked Quads, "modified" Decca ribbon tweeters and huge 21" (or 24") woofers in sealed boxes. He sold the system with his own active crossovers and, of course, bunch of amps. It was called the Mark Levinson HQD system:

http://www.marklev.com/systems/



It will be good to figure what crossover slopes and point Levinson used. AndI'll go with plasma tweeters, of course!

[glynnw]

I hope you will pardon a little reminiscence.   Over 30 years ago I was lucky enough to fall in with a group of Audiophiles in Atlanta, one of whom had the HQD system.  While it was very impressive, it never stole my heart.  That award went to another friend's system using Beveridge 3 speakers with some subs by another company.  That was the first time I ever felt like there was a person standing between the speakers singing.  But, of course, you can't go home again - 10 years ago I purchased a pair of Beveridge 3s and found that by then most of my friends' current systems sounded better.  Enjoy the quads - I have had several friends who found them addictive.

[Paul Joppa]

My guess is that the "rough" treble is mostly due to the transformer - it is extremely difficult to get a high voltage step-up ratio in the treble. I do wonder whether a separate transformer design for the treble panel would work better. A separate tube amp direct coupled could be stunning, but the voltages involved are also stunning - 1kVrms means the tube(s) must operate at 2-3kV on the plates. The bass panels need three times that.

[Doc B.]

I've had Decca ribbons and Ionovacs and I think the Ionovacs will be a more interesting match with the QUADs. I really liked my Beveridge system II...Pete Riggle has it now. And I always thought the QUAD treble sounded like plastic.

[Grainger49]

Xavier,

Electrostatics are capacitors.  They need to be formed.  Keep them turned on all the time.  The sound will change for a few weeks.

[John Roman]

Sure wish I had a mountain of money to pursue all things audio. The Quads do sound sublime!

[milosz]

I've got a pair of Quad ESL-57's and I agree with pretty much everything said here.  They look great, I think, in a retro-modern kind of way. They look like space-heaters for a Swedish moon base. I love the look with original bronze grills.

I got mine off ebay pretty cheap, picked up locally from a guy whose uncle died and left the speakers. I had to have the treble panels rebuilt, Wayne Picquet supplied the magic there.  I also use his voltage multipliers; mine were shot.  I also have his zener protection boards.

I've used a zillion amps with these. I find that they like some power; I use a Soderburg-modded Forte 4a with them, best amp I've heard with them.  Also I have a Citation II with the McShane stuff, but I prefer the bass and mids from the Forte. I sometimes use an 845 SET which is OK. I tried a Stereo 70, nice mids but lacked detail.  An AMC hybrid MOSFET-EL34 amp sounds really nice on the Quads but lacks oomph.  With the Forte the bass is fantastic, and the mids are quite liquid. Highs are almost tube-like. Highs from the Forte are a little clinical, but not grainy or harsh like many solid state amps.

The Quad's highs do not sound state-of-the-art.  I don't know if I'd go quite so far as to describe the upper registers as "plastic" but they are certainly not as textured as the better ribbons. (I've never heard an ion tweeter.  Some day!) There is no lack of treble response but the sound is kind of lifeless. My Magneplanar 3.6's have much nicer treble, but the upper bass / lower mids and mids of the Quad are so coherent it's easy to forgive their somewhat dated treble sound.  The other issue, of course, is very narrow treble dispersion.

But they are wonderful speakers, overall.