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Significant sound differences between Quad ESL 57, 1973 and 1980.

H

HeinzR

pfm Member
I bought two pairs of ESL57 in London in 1995. At that time with the help of loots, it was a large magazine for private classifieds, way before the web. By the way, I saw much more of London than any average tourist because of the trips to the addresses. It was a great time that I would not want to miss. Likewise, I had bought four Quad II, all still very original and inexpensive. Well, it was almost 30 years ago.
I have heard in the 90s very much this ESL57. For 5 years I had them "stacked" so arranged one above the other per channel in a custom made steel rack.
At that time I had close relations with Les Wong, he worked at KJ West one in New Cavendish Street in W1. Later he founded Walrus Hifi in New Quebec Street. He gave me many tips for second hand purchase and I made good purchases. Of course I had also bought many new products from him, for me and for many friends. I remember that once I had a whole Mercedes Sprinter full of good hifi products. At that time an Audiolab 8000A cost more than double in Germany. Also Spendor SP 1/2 or Cyrus amps, or a Meridian 508 CD player.
Enough of the beautiful memories...

What I want to say. I reactivated one of the two pairs of ESL57 last week. Both pairs had been dormant for 25 years, but stored very well, dry and at room temperature. My two pairs have serial numbers of 30xxx and 50xxx. To be honest, I was a little scared about reactivation...but there was no sparking, popping or any other problem.
But now it's getting interesting. I could remember the pair with the 30xxx serial numbers sounding just a little bit clearer and more natural almost 30 years ago though the 1980 pair which had even a tag that it had service at Quad in 1983.
And today? I have been listening to the 1980 pair for a week now. Nice that it plays well. It has the usual weaknesses described on the net, a bit quiet and a muffled bass. According to several websites, the bass panels were not treated with the expensive Mylar but with a cheaper ingredients, only the tweeter panel got mylar. That is why the resonant frequency of the bass panels change to the upper bass notes causing a muffled sound overall.
So I thought, ok, this is normal for a 43 year old ESL57. By the way, these speakers needed about a full day of static charging before they sounded ok.
Today I plugged in the even older 1973 pair for the first time in 30 years. I didn't have high expectations. This pair has never been in service at Quad, it is totally original. Even though you might think the diodes are weakened to reach 1500 and 6000 volts, the panels are worn out and flabby, the carbon resistors have totally gone up in ohm value...I'm shocked at how good these old things sound. And it sounded quite good after charging a few hours only. Honestly I would not change anything because they sound so open fresh and pleasant and clear that it is a pure joy. When a product has an obvious need to be restored then I immediately agree. But my gut tells me that these 1973 ESL57 still sound so good to my ears that I will not change anything, at least for the upcoming time.
In fact, I played both pairs for checking to sell them, so they work. But now I will definitely keep the 1973 pair. It is so good also in Relations to my LS 3/5a and Klipsch Lascala from 1977.

Why is the difference in durability between the 1973 pair and the 1980 pair so significant?
I don't have an explanation but it is a more than significant difference. Did Quad change anything in the material between 1973 and 1980?
Thanks for any feedback.
BTW, I listened with Quad II set to 16 ohm in the 90s (I still have them) and now with a 306, both match the ESL57 very well.
 
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What you're seeing is the dustcovers, Quad sprayed them grey to reduce reflections (presumably). Well worth removing the accumulation of dust, there is no safety issue, and if you have an accident replacement is definitely DIY. I think Quad themselves offered kits and instructions.
 
I don't know why the OPs two pairs sound different, but the first place to start would be measuring the EHT, this unit changed several times over the years and possibly they age differently.
 
Sorry. Anyway original Quad panels are sprayed on the front (( think the rear remains clear, the spraying was done after assembly before fitting the front grille).
 
May be the EHT is responsible for the clear differences. In 1995 when I purchased both pairs I had removed the grills and cleaned all the dust away which was there.
BTW which components of the ESL57 are in the signal path? Are those carbon resistors part of the xover, or some more other parts? If so, should I again use carbon resistors or is it not relevant to the sound? In this case, metal film resistors would keep their ohm values more reliable? The diodes are only to have a high voltage DC to feed the stators?
I think about the 1980 pair to restore/replace the passive electrical parts first and listen again. The panels/foils themselves are another story and not in the reach of my skills.
 
All the components in the base of the transformer are in the signal path, everything around the transformer isn't.
 
Thanks, Paul R. If I would restore the parts in the signal path (the caps and resistors) against new ones, e.g. to have correct R values is there any recommendation which nowadays purchasable types of resistors and caps match the sound of the ESL57, or is this not too relevant in this circuit?
 
Were aftermarket panels available in 1995? That seems the most obvious unless unless one set has dying EHT units (also make the 57 sound really dull). Are EHT units in good pair original? My experience is they all go off
 
HeinzR said:
Thanks, Paul R. If I would restore the parts in the signal path (the caps and resistors) against new ones, e.g. to have correct R values is there any recommendation which nowadays purchasable types of resistors and caps match the sound of the ESL57, or is this not too relevant in this circuit?
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I realise I didn't distinguish the transformers.... The audio components are under the large transformer on the left looking from the rear.

You used to be able to get sets of crossover parts from One Thing Audio, if they're still going the value was OK, compared to searching out high voltage components from elsewhere.

If you're getting in to it it may be worth looking at a protection circuit for the tweeter.
 
Dowser said:
Were aftermarket panels available in 1995? That seems the most obvious unless unless one set has dying EHT units (also make the 57 sound really dull). Are EHT units in good pair original? My experience is they all go off
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My understanding is that Quad ceased production and service fitting of their own panels circa 1997 with the jigs being sold subsequently to the ESL specialist in Germany who are still trading. I don't think that any 'new' aftermarket panels for the '57 were available until the beginning of the 21st. century. From memory, I think that 'One Thing' panels first became available around 2006.
 
Meanwhile I have saved the service manual of the ESL57 from the dada website. No one knows how long those sources exist. As you say, Paul R, at the left transformer seen from rear, the audio transformer with the speaker signal inputs are all the components which are in the signal path. Those sets from OTA would be not cheap since Brexit, not breaking the bank but I guess much higher price than a customs and shipping cost free order from Mouser in Texas.
I will have a closer look at the components and panels but since I bought this speakers in 1995 from private people and one speaker has an original tag at the back „serviced by Quad 1983“ I would assume that the panels and transformers are original. Anyway I will have a closer look at a point of time. Meanwhile I still enjoy the 1973 pair which sounds very good. It is significant that both speakers of each pair have a matching sound but only with each other. I may start with purchasing or borrowing a static volt meter to see whats the EHT values are about, 6000v and 1500v.
 
Its actually difficult enough to measure the EHT voltages accurately - most HV probes present a bit too much load and then you tend to get lower than "real" voltages. once you know that, then you can compensate for it. Sheldon Stokes has an excellent guide to all things Quad, download it and spend some time reading it over.

The EHT units will very likely be responsible for what you are hearing. If you are lucky, they will be cased in wax (so gentle heat to remove the EHT board). Replace the parts, fit back into the speaker and give them another listen.

If there is improvement then it is worth moving on to service the rest of the parts, resistors in the audio transformer, and well worth while fitting protection for the treble panel if you are in there anyway.

Only work on the panels if you have no choice....
 
fran, thank you for the recommendation. It was easy to find Sheldon Stokes Refurbishing book, a nice read for the weekend.
 
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