Reading driver displacement with radar!

[davygrvy]

Originally Posted by bentoronto

Back EMF from the voice coil (in a bridge) is better.

Such as the method described here?

[bentoronto]

Originally Posted by letsbangout

Sorry to hijack.. but what is "back EMF" ? You mean ringing? It sounds almost as if you're referring to some kind of induced radiation, a la inductive coupling from RFI.

Just like a motor. The impedance of an ordinary voice-coil speaker changes the more it moves and peaks at resonance(s). Because of back EMF, unless I have the term wrong.

Feedback from the speaker is the last great frontier - well, a great frontier, if not the last. Without feedback, you can't improve. And there's no feedback from the speakers. And today's best speakers perform as well as the best amps of 1950, on a good day.

As far as protecting speakers from being over-driven, gotta be a lot simpler ways than with radar.

[davygrvy]

To repeat again, this isn't a feedback system. Impedance also changes with temperature, too.

[letsbangout]

Originally Posted by bentoronto

Just like a motor. The impedance of an ordinary voice-coil speaker changes the more it moves and peaks at resonance(s). Because of back EMF, unless I have the term wrong.

Your terminology seems to be correct, but what you're describing is simply Ringing:

http://en.wikipedia.org/wiki/Ringing_(signal)

The paramount question though, as far as I'm concerned, is how feedback (from the driver) could possibly help reduce ringing? That's a phenomenon that occurs simply by the very nature of the driver using an inductor. You really can't stop the tendency of an inductor to ring, you can only deal with it in some way. The "standard" solution seems to be a DC-coupled amplifier, sporting an extremely high damping factor, which can tightly control the amount of current within the resonant circuit comprised by the driver - the Crown K2 is a good example of a DC-coupled amp, with a damping factor of 7000 at the low end, IIRC.

Can someone point me to a thesis statement on this feedback stuff? What might one hope to do with the feedback data - maybe throw more capacitance into the network to counteract the ring? What's the net benefit? Am I off my rocker or what?

[bentoronto]

Originally Posted by letsbangout

Your terminology seems to be correct, but what you're describing is simply Ringing:

http://en.wikipedia.org/wiki/Ringing_(signal)

The paramount question though, as far as I'm concerned, is how feedback (from the driver) could possibly help reduce ringing? That's a phenomenon that occurs simply by the very nature of the driver using an inductor. You really can't stop the tendency of an inductor to ring, you can only deal with it in some way. The "standard" solution seems to be a DC-coupled amplifier, sporting an extremely high damping factor, which can tightly control the amount of current within the resonant circuit comprised by the driver - the Crown K2 is a good example of a DC-coupled amp, with a damping factor of 7000 at the low end, IIRC.

Can someone point me to a thesis statement on this feedback stuff? What might one hope to do with the feedback data - maybe throw more capacitance into the network to counteract the ring? What's the net benefit? Am I off my rocker or what?

In the perfect Web world, posts which were top-filled with malarky would be prefaced with something like, "I think..." or "Possibly...." or as in silly olden days, "In my humble opinion..." That way, repliers ("replyers"?) would be sympathetic and will reply to misguided thoughts because the original poster was, at least, a modest person, if misguided.

Never the less, embracing the accepted, if dubious, rhetoric you find in anonymous testosterone forums in the audio (and, even worse, the motorcycle) worlds...

Look here (esp. at the download paper URL at the very bottom):
Tech

This is about capacitive motional feedback that I happen not to think highly of. But it illustrates pretty well about the topic and shows the measurements on frequency response and distortion.

Footnote: even with remote sensing to eliminate most of the speaker wire resistance (as in the Kenwood Sigma Drive feedback), you can never get help from DF over maybe 15 because the speaker voice coil DC resistance will always be in the circuit, I truly believe.

Remarkable of davygrvy not to believe you can control a loudspeaker by controlling the input to it. Remarkable, I truly believe.

[davygrvy]

bentoronto, are you done swinging your thing around?

[davygrvy]

Originally Posted by bentoronto

...rhetoric you find in anonymous testosterone forums in the audio (and, even worse, the motorcycle) worlds...

I forget the path of the USENET motorcycle forum, but their saying was "Live to flame, flame to live".

Anyways.. I would never consider a closed loop feedback system for the control of distortion using X-band radar for a number of reasons. Feedback systems can be quite fragile. The Velodyne is a fine example of such fragility.

I do like it for preventing distortion in front-loaded folded horn subs caused by only over-excursion in a PA setup where loudness is paramount because you have to run it all close to its point of death or you aren't getting the most from it.

[davygrvy]

Originally Posted by bentoronto

Remarkable of davygrvy not to believe you can control a loudspeaker by controlling the input to it.

Please describe for me the behavior of feedback at clipping? Not clipping of the amplifier, but the excursion limit of the driver.

A feedback system will just drive it harder into the damage zone. If you went the other way to reduce level rather than increase, you've gone in the correct direction for the distortion caused by over-excursion. I am controlling the input.

Ben, you have really got to get out more and make stuff.

[hellonwheels]

Mix guides monitors meyer sound x-10 Field Test-Mix reviews the meyer sound x-10 linear control room monitor in mix guides monitors meyer's take on servo (microphone in the loop)

[davygrvy]

You must attenuate to reduce distortion, not increase gain by way of feedback. So it really isn't servo