In article , Serge Auckland
wrote:
Derrick, I'm glad you found my comments helpful. That's the beauty of
these newsgroups!

Regarding the ELS63, from what you say, it sounds as if something wasn't
right,

I would agree. It did seem to me that the 909 was being asked to supply
high currents and perhaps this was due to the ESL63 protection coming inot
play when it should not.

however a few things come to mind:-

1) From your description, it isn't clear if the problem affected one or
both 'speakers, and if the 'fault' was the same on both. As the
'speakers are completely separate units, it is unlikely (but certainly
possible) for both to go wrong in the same way at the same time. In my
experience, albeit not as an ELS owner, the '63s do require service
from time to time. A close friend with a pair has had several panels
replaced over the past 10 or so years, and he certainly doesn't abuse
his 'speakers. His amp is the QUAD 306.

FWIW though, I've had a pair of ESL63s since 1984. In that time they have
not required any service, and still sound fine. They have been used with a
power amp capable of over +/-80v peak and over +/-30a peak. However I have
used them with care, and most of the time at quite low levels. My
experience therefore is that if used with care they can last a long time.

2) The ELS63 has a "crowbar" protection system. This means that if the
'speakers are being seriously overloaded or the mains isn't on, then the
'speakers present essentially an intermittent short-circuit to the amp.
This will certainly sound horrible, and if persisted with, will cause
the amp to run hot, shut down or blow up depending on how well designed
it is. If that is what happened in your case, it shows how well
engineered the 909 is that it just got hot.

For obvious reasons, Quad design their amps with current limiters so as to
be able to endure working into the 63 crowbar for extended periods. However
other designers do not always do this, and may have good reasons for
avoiding using current limiters. So this is a point worth bearing in mind
if considering a non-Quad amp.

The above should not matter if used with care, though. FWIW The amp I use
would have evaporated the crowbar device in the original ESL64's as the
current rating of the triac was well below what the amp will sustain. Yet I
have never had a problem as I simply use the speakers well within their
design limits.

What surprises me, and I don't really have an explanation, is why QUAD's
service department couldn't find anything wrong with the 'speakers if
they were as you described. One of life's mysteries!

I have been wondering about two possibilities, but they both seem 'long
shots'...

1) That when Derrick was using the 909 + ESL63's there was some 'RF' for
some reason and this was triggering the protection.

2) That for some reason the speakers were not getting the mains power to
polarise properly. This would reduce sensitivity and prompt the owner to
turn up the volume, thus leading to problems.

However apart from the above, dubious, guesses, I also find this strange.

Slainte,

Jim

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