Actually, there isn't. Both require an amplifier that's unconditionally stable, i.e. the feedback never turns positive whilst there's still loop gain available to turn it into an oscillator. It doesn't matter if the phase shift is positive or negative, and energy is stored either in the magnetic or electric fields.
We are not looking at a stored energy situation. In both cases the energy from the amplifier produces movement, although there is some residual energy which is fed back into the amplifier. The lower the amplifiers’s output impedance the better.
Hint:- Electrical energy, not mechanical energy
I have not been following this closely since it seems to have devolved into some sort of debate/pissing contest. As stated above, a square wave test into 8 ohms in parallel with 2 uF used to be a pretty standard test representing the load many speakers presented to the amplifier. The Quad ESLs shorted the input terminals (i.e. amplifier's output terminals) when overloaded. I would like to know my amplifier would survive if not thrive driving whatever speakers I have, and that means looking at the resistive and reactive components of the load. Ported speakers tend to have impedance minima around the port tuning frequency when the woofers are essentially static so a DC impedance. Through the rest of the band the impedance often varies widely (I often use the term "wildly") due to driver/crossover interaction. It all makes for a fairly complex load that the amplifier sees, and square-wave (step-response) testing is a long-used method in simulations and the real world for assessing the broadband performance of an amplifier. I am not sure exactly your issue with this.
Damping factor in this audio world (vs. the control world where it is a term in the denominator of the impulse response equation) is DF = Zload/Zsource. Z (impedance) is in general complex and depends upon frequency. Most discussions and spec sheets only provide the magnitude and often at just one frequency, sometimes a few (LF, MF, HF). If you just calculate magnitude, as is typical (and what I clearly stated in my opening posts), then phase angle affects the magnitude (since it changes the real and imaginary components of the impedances) of the speaker and the amp (and cables between them, natch). The calculation does not change, but speaker and amplifier impedance most certainly do, thus damping factor varies over frequency. Personally I prefer to look at impedances but that's the way I was weaned. Damping factor, like a single SINAD number, hides too much information.
The posts I made were not intended to get into the details relevant to engineers designing amps and speakers, but rather help introduce a lay person to the concepts. This is why I rarely post such threads much anymore; people debate their merit and nit-pick missing detail I never intended to provide (whether I know it or not, another endless debate I don't care to pursue). I was not trying to provide anything more than a basic understanding at a high level. If you already know how to design amplifiers and are familiar with all the usual feedback knowledge base then this thread is not for you. If you do not know the details and want to learn more, an Internet thread is not the place to do it IMO. It takes more advanced study and some empirical (lab) testing to gain that sort of deeper understanding.
Inductors and capacitors store energy. I do not understand your first statement, unless you are looking at only the mechanical coupling into the electrical system?
Hint electrical energy into mechanical energy to give changes in air pressure.
Yes they do but in this case that isn‘t their purpose. The electrical energy is converted into mechanical energy I.e. movement.
I guess I don't follow but need to bag this discussion. I was thinking of the crossover that the amplifier and drivers see as well as primary and parasitic electrical impedances of the drivers (amps, wires, whatever). That affects the effective damping factor.
Agreed!
It does affect DF but not much. Highest "effective" DF is 1.5 since resistance of the woofer's coil is likely 2/3 of the rated impedance at 1kHz. Crossover component involved is a choke in series, that is likely 0.1 ohm and doesn't affect DF much.
Doesn’t work like that if you have an amplifier with an output impedance of 0.8 Ohms and you connected a speaker with a nominal impedance of 8 Ohms and say the speaker cables had a resistance of 1 Ohm. The speaker and cables are connected in parallel with the amplifier the circuit impedance would be less than 0.8 Ohms.
You do know, don't you, that there is a Church of the Damping Factor out there in audiophile-land?
Sorry, but I don't understand it. Speakers and cables are connected in series with amplifier. I'm not sure what you call "circuit impedance" and speaker cables would never be 1 ohm, unless you use gage 27 (why?).
Doesn’t matter what cable resistance is the speakers are connected across the amplifiers’s output terminals so the total impedance must be smaller than the amplifiers’s output impedance. The 1ohm was just to keep the maths simple.
No it isn't!! The cables (there are two wires) are in series with the amplifier's output impedance so the output impedance as seen by the 'speaker is the sum of the two.
We exhausted it, I agree, but let me try to explain how damping works. When positive voltage is applied between plus and minus terminals of the speaker membrane goes forward with motion proportional to current (applied voltage divided by speaker's impedance). When membrane moves in the same direction on its own positive voltage is generated (back EMF) between positive and negative speaker's terminals, but this time current flows in opposite direction (since speaker is the source) producing opposite force on the membrane and braking its movement. Amount of breaking current is inversely proportional to resistance in series - speaker coil, wire, amplifier. Since speaker's impedance is many ohms a fraction of ohm in amp or speaker cable won't make much difference in braking force.
Nonsense! Series connection means the current is common to all connected components. Are you telling me the current flow in the woofer also flows through the tweeter. If it doesn’t it can’t be a series connection. Think about it before you post!
The induced EMF is opposite it polarity to the applied EMF (Lenz’s Law). The lower the amplifier’s output impedance the quicker it will damp the back EMF. Think regenerative braking in Electric Vehicles.
