Amp damping factor?

A high 'Q' speaker will sound under damped even if the amp has a damping factor of 10,000 or more.
Voltage source amps will have hi damping,
Current source amps, not so much.

I suspect that a critically damped speaker ('Q'= .707) will be good even with low damping amps.....most tube gear.

Al, isn't damping simply the instant ratio of speaker impedance and the impedance of the amp to the back EMF generated by the speaker? The amp, best case is a dead short (not possible in fact) to this back emf. Take a bare woofer driver and short out the connections with a short piece of wire and 'thump' the cone. Totally damped? yep. Remove the jumper and try again. Rings, if not quite 'like a bell' than you can certainly hear the resonance.

I work in the semiconductor fabrication industry. One of our BRAG number is what we call RDON....Resistance Device ON.....when it is conducting. Lower is 'mo betta and although a known parameter, is constantly measured and efforts made to improve it in new devices. There are of course physical limits when dealing with Silicon devices.

As an aside, Sunfire /Carver used our (company I work for) devices in the output sections of many of his amps / receivers.

1st, DF is just a spec, If all manu. measure the same, you should be able to compare. Not that this would make it mean any more or less!

Also, propagation delay is as good a reason as any why certain bi-amp combinations don't work out. 1milisecond is roughly 14" at the speed of sound and will result in phase/time smear effects. Even I can hear that! Pair a fast amp with a slow amp and you could quite possibly get to that level.

Bi,
Read the rest of this thread. Most of your questions answered.

One point NOT addressed so far is that of phase angle.
When voltage leads or lags current, power to the speaker is compromised.
Tube amps do not like capacitive loads, either.

Sensitivity, while important, may in some cases be trumped by a phase.
A high sensitivity speaker with a huge phase angle will still not be proper for a tube amp. OTOH, a low sensitivity speaker which is a moderate load, can and does sound fine with tubes. Harbeth comes to mind.

To the extent that compatibility can be decided without listening to a given combination, I'd avoid big impedance swings and low impedance coupled with high phase angles at particular frequencies when using tube amps.