I see a lot of amplifiers with extra terminals to allow "buy-wiring" to the speakers, but if you're going to put two sets of terminals on the amp anyway, why not put one at the amplifier output and the other at the feedback input. You then biwire using two identical sets of wire to the speaker and let the amplifier's feedback take care of minimizing any speaker cable effects...
Anyone ever tried this?
MR
Anyone ever tried this?
MR
The idea is good.
It would be like messuring resistens accurate with 4 wires.
This makes the resistens of the wires "invisable".
I do not know what it would do to the stability of the amp.
But the closer to you ear the feedbackpoint is located the better.
A technique used sometimes is acustic feedback,
a device mounted on the speaker cone,
senses the movement of the cone.
It would be like messuring resistens accurate with 4 wires.
This makes the resistens of the wires "invisable".
I do not know what it would do to the stability of the amp.
But the closer to you ear the feedbackpoint is located the better.
A technique used sometimes is acustic feedback,
a device mounted on the speaker cone,
senses the movement of the cone.
I have been thinking about this trick too, but it is probably not a
good idea when considering stability, risk for TIM etc. One
possibility might be to split the feedback loop so we feed back
both from the speakers and from the amp output. If we then
use a low-pass filter on the speaker feedback, and balance this
with a suitable HF boost on the OPS feedback then perhaps
we could avoid the problems. What I mean is a double feedback
á la the Leach amp, but moved one step further, from driver/OPS
to OPS/speaker. One problem is that this would have to be done
individualle for each system, since we must know the electrical
properties of the speaker cables to get this right.
good idea when considering stability, risk for TIM etc. One
possibility might be to split the feedback loop so we feed back
both from the speakers and from the amp output. If we then
use a low-pass filter on the speaker feedback, and balance this
with a suitable HF boost on the OPS feedback then perhaps
we could avoid the problems. What I mean is a double feedback
á la the Leach amp, but moved one step further, from driver/OPS
to OPS/speaker. One problem is that this would have to be done
individualle for each system, since we must know the electrical
properties of the speaker cables to get this right.
Carlos,
True but by a different amount. They wired a large value resistor across the fuse so that if the fuse blew you would have some amount of feedback to manintain dc stability. The end result is the same, to take the feedback close to speaker as possible on the assumption that feedback would reduce all non-linearities caused by wire, fuses etc.
Jam
True but by a different amount. They wired a large value resistor across the fuse so that if the fuse blew you would have some amount of feedback to manintain dc stability. The end result is the same, to take the feedback close to speaker as possible on the assumption that feedback would reduce all non-linearities caused by wire, fuses etc.
Jam
Unlike a 4 wire resistor measurement though, my feedback connection in this case must have a bandwidth that extends beyond the audio bandwidth. Any noise picked up on the return path essentially gets reflected to the input and becomes noise at the speakers.
If you were bi\tri amping with electronic cross-overs it may offer an improvement, however, the impedance of the inductors and capacitors in the speakers is likely far higher than the cables connecting to them.
Just some thoughts...
Alvaius
If you were bi\tri amping with electronic cross-overs it may offer an improvement, however, the impedance of the inductors and capacitors in the speakers is likely far higher than the cables connecting to them.
Just some thoughts...
Alvaius
Re: Speaker feedback
This approach has been around a long time for turning an
amp into a constant current source or otherwise raising it's
output impedance.
But it is not the same thing as discussed above. I believe the
thread is addressing the means of enclosing the cables in a
feedback loop so as to lower their impedance.
This is not difficult to do as long as the circuit is very stable
otherwise and the amount of feedback around the cable
is kept at modest levels.
carlmart said:
This approach has been around a long time for turning an
amp into a constant current source or otherwise raising it's
output impedance.
But it is not the same thing as discussed above. I believe the
thread is addressing the means of enclosing the cables in a
feedback loop so as to lower their impedance.
This is not difficult to do as long as the circuit is very stable
otherwise and the amount of feedback around the cable
is kept at modest levels.
Hi alvaius,
Sorry that this has nothing to do with this thread. But I haven't heard from you about your G4 x-overs for 3 weeks. How's it going with the x-overs? Somebody e-mailed me a little while ago about building some G4's and he says that Graham says that the 10 db spike at 3,750 Hz goes down to 2 db after 200 hours break in although I have noticed this I think. Just wanted to tell you maybe this will and you and later also myself.
Sorry that this has nothing to do with this thread. But I haven't heard from you about your G4 x-overs for 3 weeks. How's it going with the x-overs? Somebody e-mailed me a little while ago about building some G4's and he says that Graham says that the 10 db spike at 3,750 Hz goes down to 2 db after 200 hours break in although I have noticed this I think. Just wanted to tell you maybe this will and you and later also myself.
Other British outfit
Don't think that DNM have ever used a feedback loop containing the speaker cable. The other British outfit that Werner is referring to is Deltec - unfortunately no longer in existence. They specified their own speaker cable - Black Slink. This was a well regarded Goretex dielectric cable.
James
Don't think that DNM have ever used a feedback loop containing the speaker cable. The other British outfit that Werner is referring to is Deltec - unfortunately no longer in existence. They specified their own speaker cable - Black Slink. This was a well regarded Goretex dielectric cable.
James
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