One for Phil
Mike Maxwell
section on the modifications that the SME boss, Mr Robertson-Aikman made
to his ESL 63's. I don't know if you're interested but if you are I can
put them up here for you (and all the Quad lovers) to have a look at.
Mike.
Phil Allison
"Mike Maxwell" <one...@netscape.net> wrote in message
news:3DB64D0B...@netscape.net...
** Dont be a tease Mike, that is very naughty.
Go on, post it .
. . . . . .. . . .............. Phil
Mike Maxwell
Ok, here goes - it's long. (As a preface, here's a bit about how his two
pairs of speakers are set up. The main pair faces forward, while the
second pair - positioned behind the front and close to side wall - fire
to the sides and produce very little signal; the additional speakers are
there just to augment and fill-in the sound.)
DON'T TRY THIS AT HOME. In many respect the Quad ESL-63 Loudspeaker is
considered without equal but in its standard form the requirements of
safety and transportability impose inevitable limitations.
Firstly, the stockings, metal grilles and Mylar dust covers were
dispensed with, the environment being sufficiently clean to permit this
course of action! Thus revealed, the plate assembly can be seen to
resonate at low frequency, the excursion being easily visible. The
assembly is compliantly mounted within the frame; a feature which a
purist might find hard to defend. As modified it is rigidly clamped by
transverse reinforcing beams, arranged three in front and behind the
speaker. Each pair of beams is clamped together with HT insulated socket
screws. There is no reduction of radiating area as the beams coincide
with flanges where the four plate units join. Clamping screws pass
through holes centred on the split lines. Top and bottom edges of the
beams are backed off at 10 degrees to assist dispersion.
Beams are made of brass and each set weighs about 70lbs, increasing the
effective mass of the plate assembly. They are lipped onto the metal
frame at each end and critically dimensioned so that besides reinforcing
the assembly they clamp it to the frame. Effective mass of the whole
assembly is then raised with a 100lb billet of steel on top of each
speaker.
The effect of these changes is significant. Voices have a more natural
quality without low frequency excitation, bass is true and extended. It
is interesting, too, that power handling is improved because with plates
held firmly, better diaphragm spacing is maintained. The foregoing notes
are note intended as instruction for the work, which should not be
attempted unless engineering facilities are available. It must be
remembered too that without the grilles, there is a high risk of
electric shock which can continue after the unit is disconnected from
the mains. It is regrettable that only when normal constraints of safety
and transportability can be dispensed with that the potential of this
remarkable speaker can be realised.
All four ESL-63s are secured on stands about 10in above floor level. The
system operates behind acoustically-transparent curtains with very
convincing results. Placement, both in relation to the room and each
other, is critical and input modifications are necessary for subjective
harmony.
Alastair, upon commenting on the resistor network, stated that, "The
standard speaker employs a small resistor/capacitor network consisting
of a 1R5 across 220uF. The choice of value for these components allows
the bass to be equalised with the mid range and treble. The resistor
also provides protection for the amplifier.
"In my system advantage has been taken of the equalisation possibilities
particularly important with four speakers. The brand of capacitors
selected were only available in 10uF and had the be multiplied as
required. I started with seventeen but due to their efficiency , seven
had to be disconnected before the right balance was achieved. Also the
load resistor is 1R instead of the standard 1R5, to lower rise
cross-over frequency for my particular system."
I hope some of this makes sense. I might fire up the scanner later so I
can put a picture to the description if you're interested.
Mike.
MDHJWH
Snip>
>
> DON'T TRY THIS AT HOME. In many respect the Quad ESL-63 Loudspeaker is
> considered without equal but in its standard form the requirements of
> safety and transportability impose inevitable limitations.
>
> Firstly, the stockings, metal grilles and Mylar dust covers were
> dispensed with, the environment being sufficiently clean to permit this
> course of action! Thus revealed, the plate assembly can be seen to
> resonate at low frequency, the excursion being easily visible.<. . .big snip
I had John Hall attempt a similar mod on mine with disasterous
results. They came across to me as more detailed (who would have
thought that possible) but tilted up in the treble. Frequent arcing
ensued at a rate worse than the old ESL's. After being a guinea pig
for mumerous itterations of mods with different materials I gave up.
They now sit upstairs unusable and in bits. I've communicated with a
few gents on US news groups about a German & various other companies
that do repairs. At the moment I'm undecided as to what to do with
them as even with REL subs I found them not up to cathedral organ duty
etc (The RELS always seemed to be late in catching up) When repaired I
may end up giving them to a friend who has Quad valve pre and powers
amps, is impoverished and besotted with everything Quad.
My memory is not to be relied upon but I recall the original Quads
ESLs as being more neutral buts lots more lacking in grunt. However
the ones I was exposed to were stacked piars and at that age I was
easily impressed.OK some of you will say who wouldn't be.:-}
It's claimed that accurate acoustic memory lasts only minutes - not
years. (Decades later I may be a bit down in hearing sesitivity at the
upper limits as well)
Ayn Marx
Phil Allison
"MDHJWH" <mdh...@iprimus.com.au> wrote in message
news:808df0f8.02102...@posting.google.com...
(snip sad story about some Quads)
> It's claimed that accurate acoustic memory lasts only minutes - not
> years.
** It lasts only moments - not even seconds. The repetition of any
musical passage sounds different to most listeners most times.
That is why I an instant and seemless changeover switch is the
best method.
. . . . . .......... Phil