Damping Factor

Damping factor is the ability of the power source to control the unwanted movement of the woofer. IE: the woofer only moves when the signal sez, not just because it is out of control. High damping factor=control. And yes a factor of 10 is adequate.. just a factor of 1000 is a LOT more than adequate

Is "zero feedback" in an amplifier design referring to damping in any way?

Damping Factor is directly related to Amplifier Output Impedance. It is not possible to make an acceptable Solid State Amplifier without providing negative feedback. It is however possible to make a reasonably good Valve or Tube Amplifier without negative feedback, or "Zero Feedback". This amplifier, if correctly loaded, meaning the output transformer ratio is such that all available power is transferred to the speaker load will have a damping factor of 1. Adding negative feedback will lower the output impedance and increase the damping factor, it will also in most cases lower the distortion, but it will not increase the output power. Valve or Tube Amplifiers usually have only moderate amounts of negative feedback, resulting in a damping factor around 10. Solid State Amps on the other hand usually have massive amounts of negative feedback in order for them to work at all, giving a high damping factor.
Large amounts of negative feedback generally lower distortion at mid frequencies and tends to "Hide" crossover artifacts. In other words, it makes a fairly ordinary amplifier "Spec-Up Well" on test instruments, but unfortunately does not necessarily make an amplifier sound good driving real speakers playing real music. A high Damping Factor is something you get for free from most solid state amplifiers, not necessarily something you need.
A Damping factor of around 10 is sufficient.

Damping factor is the ratio of the load impedance to the amplifier's output impedance. But you also have to figure in the resistance of the speaker cable to get your "real world" damping factor. IMO, 20 or better is my minimum goal, but 50 or better is my target.

BTW, solid state amps don't use that much negative feedback anymore. At least those that are designed by competent engineers who've paid attention over the past 20 years or so.

Thanks Poulkirk, for an answer that I can mostly understand. I have always wondered this about tube and some SS designs, in regard to the bass response.