The damping factor and the sound of real music
I was sorry to hear that Alastair had passed on. He was quite a
character!
Anyway, I'm going to type up the standard SME Quad modification
response for the 63 from The Closest Approach: (Bear with my poor
typing)
"In many respsects the Quad EST-63 Loudspeaker is considered without
eqaal but in its standard form the requirements of safety and
transportability impose inevitable limitations. The following notes
outline modificaitons made o the four ESL-63s installed in the Music
Room of SME's Managing Director, Alastair Robertson-Aikman.
Firstly, the stocking, metal grilles, and Mylar dust covers were
dispensed with, the local 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. Notwithstanding that,
the assembly lacks stiffness, and it 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 three behind each speaker. Each pair of
beams is clamped togther with high voltage insultated socked screws.
There is no reduction of radiating area as the beams coincide with the
three sets of flanges where th four plate units butt together. The
clamping screws pass through holes centered on the split lines. The
top and bottom edges of the beams are backed off at an angle 10
degress to assist dispersion.
The beams are made of brass and each set weights about 70 lbs.,
greating increasing the effective mass of the plate assembly. The are
lipped onto the metal frame at each end and critically dimensioned so
that besides reinforcing the plate assembly they also clamp it to the
frame. The effice mass of the whole assembly is then raised further
with 100 lbs. of billet steel attached to the top of each speaker.
The effect of these changes is significant. Voice have a more natural
quality without low frequency excitation and bass is true and
extended. It is interesting, too, that power handling is improved
because, with the plates held firmly, better diap[hragm spacing is
maintained.
The foregoing notes are only intended to outline what has been done.
They are not in anyway intended as an instruction for the work, which
should not be attempted unless technical and engineering facilities
are available. It must be remembered, too, that without the
protection normally afforted by the grilles, etc, there is a high risk
of electric shock which can continue for some time after the unit is
swiched off or disconnected from the mains. It is regrettable that
only when the normal constraints of safety and transportability can be
dispensed with that the further potential of this remarkable
loudspeaker can be realized.
In the system referred to, four ESL-63s are used, two arranged int he
normal mode an the other two outboard and at right angles to them.
All are securely supported about 10 inches above floor level. The
system operated behind acoustically transparent curtains with very
convincing results. Speaker placement, both in relation to the room
and each other, is very critical and some input modifications are
necessary to achieve subjective harmoney. A dedicated listening room
of generous size is a further requirement."
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Linear Mode
