Long term serviceability of ESLs

[rick57]

Hi

I was offered some 2nd hand ESLs which currently sound very good, but have had a lot of use, and were made by local guy here in Australia who has now retired. I asked the owner about long term serviceability. He replied:

“Long term serviceability is NIL. Alan Moss in poor health so cannot assist further. He has spare transformers which he might be persuaded to part with for the other two panels which I had stacked.

There are a couple of potential problems with the panels -

(1) the Mylar can "soften" and so give rise to a buzzing sound. Easily fixed by squirting a small amount of Silastic in to the offending part so it is effectively glued.

(2) the contact strip to the Mylar can lose contact. Not so easily fixed by using a little aluminium strip to the Mylar and changing the small wire to this instead of the original contact strip. This has been performed successfully on one panel.”


I don’t know much about ESL serviceability, but imagine the trannies could go (might they be dear?), but don’t know what other factors to consider – what might they be?

They’re interstate so I can’t inspect them now, but the guy is in our local Audio Club so I would get honest answers to any questions.

Thanks

[rick57]

I have read further :

"Unfortunately this design has a weakness – the contact with the membrane becomes corroded and there is no simple repair.

It is being kept functioning at the moment by poking a wire through the mesh onto the mylar but that is not very satisfactory as any movement can cause shorting.”

How repairable is this??

Thanks

[EC8010]

A typical ESL panel consists of two pieces of perforated aluminium, a plastic stator frame, and a tensioned diaphragm. The parts cost isn't high. What you're paying for is the ability to actually make it work. Many years ago I made ESL hadphones and had terrible trouble getting equal sensitivities. I've seen other ESL builders have the same problem.

View your loudspeakers as a "proof of concept" that may have to be totally rebuilt in the future and pay an appropriate price.

You have a considerable advantage in that it's a whole lot easier to make ESLs work in Oz than in damp Britain.

[rick57]

Hi EC8010

(Melbourne winters in *southern Oz are not as bad as the UK, but they are often cloudy, drizzly & damp, and these speakers have always lived in Launceston, Aus - maybe similar to northern Portugal).

Yes, they are only about GBP 400 for a pair, but:
- They are a lot bulkier (1500 H * 570 W) than the West Australian ER Audio kits, which I was considering doing.

- More importantly, I do not want a "proof of concept".
I simply want something preferably 2nd hand commercial, not as much as Quads, that if need be - should be r* repairable.

Is it possible to say, without seeing them, how easy it could be to fix a contact with the membrane that’s corroded?

Thanks

[EC8010]

Anything to do with the diaphragm is difficult. You'll have to make the final choice, but I wouldn't pay £400 for them in that condition.

Sorry to hear it's almost as soggy there as it is here...

[I_Forgot]

Long term operability of ESLs has been one of my areas of interest for several years. Here's what I can tell you from my limited experience with my self-made ESLs and my Quad ESL-63s:

The main point of failure will always be the diaphragms. They are under very high mechanical tension. In my Quads, the diaphragms are failing one by one so I keep opening them up and replacing them as they go (4 per speaker). The failure mode is usually a split in the diaphragm along the edge of the insulator that supports the stators. I would expect this sort of failure in my self-built speakers as well, but they are not old enough yet.

The diaphragms don't loosen or soften on their own if they are made of polyester film which most or all commercial speakers use. What can happen is the adhesive that attaches the diaphragm to its frame can let go. Some speakers, like the Quads, use something like super-glue which does not properly bond with the diaphragm material. I am amazed they were able to actually ship the things without all the diaphragms popping loose.

Some more recently manufactured speakers use foam tape as diaphragm supports throughout the middle of the speaker. I have no experience with the specific tape they use, but I don't trust it to last more than a couple years. That stuff usually fails by hardening, then crumbling. Why anyone would make a speaker that way (or foam surrounds on woofers, for that matter) is beyond me.

The other common failure point is the HV bias supply. Sometimes in order to save a few cents the manufacturer will use diodes that are just able to withstand the voltages in the supply instead of using more conservatively rated parts. Forunately, the diodes are cheap and you can afford to replace them all should one fail.

Transformers fail occasionally, if you use a much too big power amp to try to drive the speakers to ear splitting volumes and burn them up. If you stay within the manufacturer's specs on the amp you'll probably never experience a transformer failure. In general transformers are extremely reliable components, even beating electric motors (their bearings eventually fail).

Diaphragm contacts are usually either a wire or metal foil strip embedded along the edge of the speaker inside the frame that supports the diaphragm. They can usually be easily replaced with some copper tape or wire or almost any other conductor. The diaphragm is usually glued to one side of the insulator frame, the side that doesn't have the contact, so you can usually disassemble the driver leaving the diaphragm in tact and repair the contact. Contacts corrode if the + terminal of the bias supply is connected to the diaphragm. I have found that by connecting the - terminal, the contact will not corrode.

Serviceablity is a question of your own ability and willingness to commit either the time to do the work yourself or the money to pay someone else to do it. Most of the problems can be fixed relatively easily and cheaply yourself if you are willing to learn a little and do the work. The materials and parts are pretty cheap, and uncritical in nature.

If the audio transformers are good, you can make the speaker work like new. If the audio transformers are bad, you can buy the speakers cheaply and use them as a basis for your own project.

See the web page at mark.rehorst.com for a DIY article (that needs to be updated) on making ESLs. The commercial ones work in exactly the same way as the home-made ones.

I_F

[SY]

Asa side note, 400GBP (about US$750) is more than enough to get a nice set of Acoustats...

Given the situation here, if I couldn't find Acoustats in Oz, I'd just buy some transformers, eggcrate, wire, and polyester film and build my own; you're going to end up doing that anyway, and $750 is a whole lot of money for two transformers and some stators.

[rick57]

Hi I_F

Thanks, excellent information!

At what age have you found diaphragm failure begins at? Is the symptom – loss of sound from that one diaphragm, or the whole speaker?

> I have found that by connecting the - terminal, the contact will not corrode.

. . and there are no –ve effects (pun intended)?

You’d have to very lucky to get Acoustats here. I had been considering doing an ER Audio kit.

BTW, I paid a deposit on these just half an hour before seeing these last 3 posts!

The speakers are 8 years old, 7 segment, 7 sq feet (0.7 m2) per speaker, with lead lining on the timber frames. About 86 dB down to 250-300 Hz. (There is Mylar in their construction; I believe the diaphragm).
For $US 870 I also got a pair of 15 years old (one rebuilt later) spare panels and spare transformer & two circuit boards + circuits from the maker.

By buying something made, my time is freed for (too many) other projects . .

deposit paid > too late now . . . how does that sound for value?

Regards

they wouldn't win beauty awards close up, they sound *very *nice

[rick57]

the face is ok (this is a spare panel, the streak is a reflection)

[rick57]

the trannie box, could do with some orange oil