> I have a pair of bi-amped Tannoys... but not the sort you allude to.
> Mine are 638s (8" DC & 8" woofer in a trapezoidal dual-chamber reflex
> cabinet) driven by a couple of home made MOSFET amps and a home made
> active crossover. I like them ;)
As well you should! Nothing shabby about that setup at all.
A problem with the old Tannoys, especially the concentric ones, is the
cones falling apart. The rebuilts can sound very good, but just
different. One Kleenex hanging in front of the speaker is a way to get
the new cones to match the old cones--kinda like the NS10 trick. I
just love the way these things seem to move the soundfield away from
the speaker plane itself. The sound seems to originate from the open
air. Another thing I like about them is how the highs and lows stay
unified in timing. Going off-axis doesn't change the imaging where
instruments will move around the sound stage. This is especially
critical with 96/24 recording or analog master disks or high-speed
tape recordings. With most speakers, if you change your listening
position by 10 degrees in relationship to the speakers, the sound
stage will shift to the point where instruments will change position.
The Tannoys with time-aligned concentric speaker-cones generally do
not do this. If you are sitting still, any speaker design will do. But
if you move your listening position for any reason, the sound stage
will shift position as you depart from the time-aligned sweet spot.
> I hear that Paul McCartney nabbed a pair from Abbey Road, which gives
> you some idea of how high & mighty you have to be ;) Best bet is
> probably to try and score an old pair of Lancasters, chuck the cabs on
> a bonfire and build something decent yourself to put them in. Maybe
> I'll do that myself one day.
I encountered one set of Lancasters in a studio down in Nashville.
They were mounted two feet of concrete. Not really an "at home"
installation idea.
> Surely a solid state amp with negative feedback can sink
> the current generated by the voice coil very effectively, giving it a
> near-zero output impedance and heavily damping the cone movement,
> whereas a valve (tube) output stage has to have an output transformer
> that lies outside any feedback loop and thus it's secondary winding DC
> resistance contributes to the output impedance and reduces its ability
> to damp the speaker cone?
Yes. But with the solid-state amplifier, empirical evidence shows us
that it takes many times more than what the math would indicate
necessary. It's easy to move all speaker cones in unison, but it's
very difficult to keep the rebound the same.
When presented with a constant signal, such as a tone or noise, the
amplifer is always moving the transducers. This constant signal is
forcing the speaker cones to always be moving from the + to - sides of
neutral. When a system is measured for THD with constant signal, even
a piece of trash from Radio Shack will measure out great if you allow
the system to stabilize and take the measurement long after the tone
is initiated. But if you apply an impulse signal to the speakers, this
is where the rebound can be so severe that THD is measurable in whole
digits.
Which brings up the subject of bias voltage to force the speaker cones
to ride just one side of neutral.
Of course, we can just forgo this whole discussion and go over to
Fernando's house to listen to his sound system.
:)
AG
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