Quad ESL 57 owner from London

[Osborn]

Greetings all.
Have owned original ESLs from new since 1980. Since when they have been serviced and refurbished by Quad, One Thing Audio - and more recently I have purchased a newly refurbished set of bass panels from a restorer in the United States. One of his four refurbished bass panels misbehaved, most obviously when dealing with the lower frequencies (around and below 100 Hz), even when the volume setting was moderate. Spits and ticks, most noticeable when there was little else going on in the mid to high frequencies. Sent it back to the restorer, and his recently received replacement does exactly the same thing...... Am using a Lyngdorf TDAi 2200 amp to run them. So, it shouldn't be a 'load' issue, and the other three new bass panels are fine. ....I suspect it is a leaky panel, but I can't see any blue sparks or coronas from the panel or its immediate surroundings when the room is dark (allegedly a good way to identify a leaky panel). Does anyone know a sure-fire way of confirming whether a bass panel is leaky or not? And if it is a leaky panel, what if anything can be done to rectify the problem by someone (myself) with good DIY skills (soldering included - and have replaced dustcovers on ESL 57 panels before)
Many thanks
Geoff

[Firebottle]

Hi Jonathan, welcome to the forum.

I also have ESL57's and wouldn't part with them. To assess the bass panel you really need to measure the EHT voltage to see if or how much it has sagged.
This needs specialist equipment due to the very high voltage.

I fitted my stats with aftermarket EHT boards that include neon indicators which flash to show any/how much leakage there is, a clever little inclusion.

One of my panels was leaky and I tracked it down to a corroded rivet in the panel, caused by cat wee from years before. I just removed the offending rivet then re-sealed the covers on the panel. I still have a little leakage as i forgot to clean out the rivet hole, but it isn't a big deal.

Cheers,
Alan

[Barry]

Hi Jonathan, welcome to the forum.

I also have ESL57's and wouldn't part with them. To assess the bass panel you really need to measure the EHT voltage to see if or how much it has sagged.
This needs specialist equipment due to the very high voltage.

I fitted my stats with aftermarket EHT boards that include neon indicators which flash to show any/how much leakage there is, a clever little inclusion.

One of my panels was leaky and I tracked it down to a corroded rivet in the panel, caused by cat wee from years before. I just removed the offending rivet then re-sealed the covers on the panel. I still have a little leakage as i forgot to clean out the rivet hole, but it isn't a big deal.

Cheers,
Alan

I hope you got rid of the incontinent cat as well.

But seriously what you have written is good advice. I too use a pair of ESL57s, bought in 1974 and they have been in constant use since purchase.

They have behaved perfectly, apart from one brief occasion (sometime in the early '80s) when I heard one bass panel "raining". The weather at the time had been hot and humid, but when it cooled the problem disappeared and hasn't returned.

I don't know the specification of the Lyngdorf amplifier you use Jonathan, but Quad 57s must only be used with amplifiers whose maximum output voltage is no greater than 30V peak.

Were it me, I would have the offending speaker sent to One Thing Audio for repair. Don't send it to Quad - they outsource all refurbishment work of 57s to One Thing Audio anyway; so that would only increase the turn around time, as well, perhaps, paying a handling charge.

Welcome to Aos Jonathan, hope you get your speaker sorted out soon - they really are special.

[Elephantears]

Don't send it to Quad - they outsource all refurbishment work of 57s to One Thing Audio anyway; so that would only increase the turn around time, as well, perhaps, paying a handling charge.

What is your evidence for this claim? Quad not only did all the work on my 63s themselves, but they insisted that they use a completely different method to One Thing. The way that they bond the stators is not the same.

[Wakefield Turntables]

Another owner ere welcome to the club

[Barry]

What is your evidence for this claim? Quad not only did all the work on my 63s themselves, but they insisted that they use a completely different method to One Thing. The way that they bond the stators is not the same.

Quad sold the manufacturing and assembly jigs for the 57s to a company in Germany. I was not talking about the 63s or later Quad designs, only the 57s.

The outsourcing of repair work of 57s to One Thing is what I read in one of the magazines - I can't speak from experience.

[Osborn]

Thanks all for the welcome - and speedy replies. I'm wondering if it may be a case of dirt of some kind inside the stators. I've had the frame and dustcovers off (a simple operation) to carefully hoover out any dirt that may have been on the outside of the stators, or lodged in the stator perforations.... but that made no difference. .....Although I have tinkered with a few bass panels in my time, I have never got as far as separating the stators and cleaning the diaphragm - and I'm a little nervous about doing it. Doing it looks straightforward enough: remove the perimeter seal (duct tape I guess) which holds them together at the edges, and the two vertical runs of bolts and nuts which hold them together at the centre. And presumably the stators will come apart. Anyone ever done this? And got any warnings about doing it?
Cheers
Jonathan

[Osborn]

Alan - can I ask where you got your EHT boards with neons to indicate leakage? I seem to remember Arend Jan doing boards like that, but sadly he is no more.....

Barry - Re the voltage output from the Lyngdorf amp - this is what it says in the owner's manual: 'When the TDAI 2200 is operating, there is up to 35V DC on its output terminals with reference to ground'... The ESLs are fitted with clamp boards, so I guess that isn't the problem (but I may well be wrong!). I've also tried the offending bass panels with other amps, and the problem remains the same.
Cheers
Jonathan

[Barry]

Jonathan,

Have you seen this: http://www.quadesl.com/pdf/quad_book.pdf ? Probably the most definitive guide to the Quad ESL I have seen.

If you look at the circuit diagram you will see that the speaker input terminals are 'floating', so the 35V DC offset (with respect to ground) of your amp won't be a problem. What I need to know is the maximum AC signal voltage of your amplifier. If it is any greater than 33V it will almost certainly damage the speaker, and it is usually the bass panels that are vulnerable because the transformer feeding them has a higher turns ratio than that for the treble and mid-range panels.

[Osborn]

Thankyou Barry for the link to the SS guide. Yes, I had seen it, looking for ways to help me to understand whether and how to disassemble the bass panels, but the bass panels in the guide are old - and in need of refurbishing - the ones I have here aren't in need of refurbishing because thay have just been refurbished..... So, while I agree that it is a brilliant guide to refurbishing the ESL in general, in this instance, it doesn't have a great deal to offer me.

There is no info in the Lyngdorf owner's manual about maximum AC signal voltage. Forgive me, are we talking about audio signal power output here? ... As in - watts per channel - if so, it is max 200 p.c into 8 ohms. There is one contributor to this board who has claimed that the TDAi 2200 and the ESL 57 is a match made in heaven (or words to that effect)