In article , Eeyore
wrote:


Jim Lesurf wrote:
[snip SCAMP comments]

It isn't a new problem. But speaker manufacturers simply tend to lob
the ball into the court of the amplifier designer and smile sweetly. I
can't complain too much as I've always favoured QUAD ESLs. :-)

How far do they swing ? Which model even ?

In my case I used to use an early pair of the original QUADs. These weren't
even a stereo pair. One had been bought in mono days, and the other to go
with it when stereo arrived. They were then used as test loads, etc, at
Armstrong before I took them home for domestic used. I did once set fire to
one of them whilst testing an amplifier. Acoustical phoned me up when it
was sent for repair and asked me in a suitably astonished voice just what
the deleted I'd been up to. :-) Sounded fine again after repair.
Curiously, it also sounded OK for a while when flames were coming out of
it. 8-] I had been deliberately using its transformer saturation as a
nasty load to see the power amp I was working on would survive. It did.

Later on I changed to ESL63s for the main hifi, one of the early issue
boards, but I can't recall the iss number off hand. IIRC one of the
versions where the LF impedance is signal level dependent. Plus I now also
have a pair of 988s for the living room AV system.

Years back I did the crossover design for a modest 'bookshelf' monitor
style speaker using Mathcad.. It's all 'impedance corrected'. I haven't
actually run a test myself as it happens (although my colleague did some
'empirical ones' and found the impedance curve very flat using spot test
tones but aside from the usual LF peak, it should be as close to
resistive as possible.

As a result it sounds sweet even on cheap amps.

It can be done. Alas, most speaker manufacturers don't bother. Simpler from
their POV not to. Just dump the problem onto the amp, and let someone
else's product require more work and cost.

Slainte,

Jim

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