On Monday, June 17, 2013 4:52:32 AM UTC+1, Jimmy wrote:
Dear Pat,
I read your article about Quad ESL and tube amplifier online. I've discussion recently with my friends about stacking Quad ESL 57 and some even thinking to stack 4 x ESL 57 in a big room and I'm interested in that since I have 2 in stacking now.
They suggest wired in series for the stacking....and sent me this link:
http://forum.audiogon.com/cgi-bin/fr...openflup&5&4#5
I wonder 3 ESL 57 stacking and series wired still ok since the impedance still 30 ohm range. However, 4 in stacking, no kidding the impedance will rise to 60 ohm and maximum can go up to 120 ohm on the low frequency.
Some even says 300B push pull can drive it!!
Gee...are they making a joke with me??
Regards,
JL
Jimmy, that's an interesting idea you have, but it's interesting in the sense of all wrong. First of all, you strike me as an innocent wandering down a rough street with your wallet in one hand and your dick in the other. Normally, in audio this would not matter if you have plenty of money. But in the case of Quad ESL you're intending to dabble dangerously in irreplaceable antiques in very limited supply. This is not a sensitive thing to do.
Secondly, you just don't have the knowledge necessary to do the job right. What you need, if you insist on running with the Joneses, your even more ignorant pals, is to find some local expert who knows what he's doing (those will give a guarantee, and pay to fix what they break) to make and maintain the installation for. I've had ESL, and mine were in no danger, but keeping yours running in this stacking scheme of yours will be about as expensive as maintaining a 68ft yacht, which I found akin to standing under a cold shower tearing up large denomination bills.
Turning from the generalities to the specifics, the QUAD ESL is specifically a speaker for delivering the classics at realistic volumes. One ESL is enough to fill a 270 sq ft room at normal orchestral volume; two just provides stereo and a fractional improvement in sound quality that is far, far below even the threshhold of perception of someone as cultured as me. To use an ESL for some unintended purpose which requires multiple ESL, say playing rock'n'roll very loudly, is barbaric.
In a much larger room, a stack of two ESL per side may be justified, especially if the ceiling is so high that the stacked ESL may be raised about head height and then angled onto the listening chair. But why should you want such a large listening room? ESL give their best to one or two listeners at a time, not crowds. ESL are not showpiece loudspeakers; they're speakers for people who have nothing left to prove.
A stack of four ESL, even abstracting from the horrendous drive problems you've been adequately informed about by the resident experts, will tend to sound much like an array. If you really need (because your listening room is huge) or want an array, there are many vastly cheaper and more efficient and less space-consuming ways of building an array than using ESL. See my article on Bessel Arrays at
http://www.audio-talk.co.uk/fiultra/...n%20BESSEL.htm
So what it comes down to is that if you're not listening to classical music or solo voices or the like, ESL are best left to those who can use them better, and the only time you can use more than two stacked ESL per side is if your listening room is ostentatiously huge.
Now, about driving ESL. The best and least troublesome ESL drivers are the current-dumping QUAD amps. If you insist on tubes, the choice way to spend your money is on sourcing and rebuilding genuine QUAD II and, failing that, get the copies manufactured by QUAD in recent years, which aren't as good but close enough for your purposes.
Yes, you can make a SET amp do the business with ESL, including with stacked ESL, and yes, you can do it with 300Bs. But you really need to know what you're doing, and you can't go buying commercial amps, you're talking about custom amps. Go to
http://www.audio-talk.co.uk/fiultra/...0ON%20AMPS.htm and scroll down to T39-KISS-300B-Ultrafi -- this is a ZNFB WE 300B amp run so high and hot to flatten the response curve that the output is only 3.8W. (It's actually the booster or power pre-amp of my 80W ZNFB SET tube amp, but that one is so dangerous, I'm not sharing the plan any more.) Now imagine stacking up five or six of these extremely wasteful 300B amps per side to drive you ESL. Utter madness just about covers it. And the heat all these tubes will give off will be a bitch to handle, probably requiring a locked, air-conditioned room all to themselves.
If you give up the ZNFB idea, you can still have SET and tubes, but it will be pricey because, if you want low NFB, you have to sacrifice power, and very likely you'll be sacrificing tube longevity too. Whichever way you turn, you're looking at serious maintenance issues.
The ESL gets its special sound from three features: that it is a point-source speaker, that it has a large area, and that operates high and hot for a flat transfer curve. There are horn drivers that make an excellent point source if suitably cased. As I write this, I'm listening to a horn of my own devising that started out something like a Lowther Fidelio bicor (this is the KISS 194 T91HWAF3 on the same page on which you've already found the 300B amp I'm using to drive it --
http://www.audio-talk.co.uk/fiultra/...20T91HWAF3.jpg will take you directly to photo of the innards under construction). It makes a good fist of the ESL sound, with a deeper bass. Larger horns, like the Westminster, can fill very large rooms and go much lower.. If you have space for a larger speaker and you want to make a cheap experiment to grasp how much (or little) a point source speaker can sound like an ESL, but louder, you can do it with some wood and a carefully selected but cheap guitar driver. See The Impresario on
http://www.audio-talk.co.uk/fiultra/...0ON%20AMPS.htm
In summary then:
If you need multi-stacked ESL, you are misusing the ESL, and you need different speakers.
You can drive single or stacked ESL with ZNFB SET amps if you can deal with the heat and don't mind keeping your amplifier technician in luxury for the rest of his life. It's smarter to use QUAD current dumping silicon amps, and better to use QUAD II tube amps. Other tube amps that will sound right on ESL will need to be custom built, and require that you first educate yourself because otherwise how will you order them built?
Sorry if this sounds like tough love, but you're walking in a minefield and you're speaking to the survivors who've come out the other side -- and we can't help shuddering at your naiveté.
Good luck.
Andre Jute
http://coolmainpress.com/ajwriting/
http://www.audio-talk.co.uk/fiultra/...0ON%20AMPS.htm