Solo ULDE

Damping factor assumes the reverse current is able to control the movement of a spring.

It has no relation to anything.

What is the springiness of the cone and what is the measure used?

Also it varies as in sealed cabinets, open baffles, horns, reflex etc.

Also cone mass.

If damping factor is effective why can I apply the same force to a cone with the speaker wires connected or not connected?

So, from my experiments it all seems a little pointless. I made a DC coupled amp and an AC coupled amp to test resonant frequencies in conjunction with an AC meter. I should have got different results at the frequencies I was reading (low) because the AC coupled amp became more "resistive" at lower frequencies (capacitive reactance), but I couldn't resolve any difference.

By using the old fashioned 100 Ohm resistor (the good old test method), I was able to resolve the resonant frequency of the drive unit which correlated with the spec.

That gave a damping factor of 0.08!

At 4.5 Hz into 8 Ohms the Proprius "damping factor" is unity (1). So choose your frequency, divide it by 4.5 and you get the "damping factor" at that frequency.

With DC coupled it's different... Oh, really? Kirchhoff states current flows in circles, and therefore load current must flow back to its source... via it's power supply capacitor...

So all amps are AC coupled to a degree, which makes a mockery of "damping factor" which is simply a calculation of the perceived output impedance in relation to the speaker impedance. And if you perceive a low enough output impedance without considering Krchhoff then iy can be whatever you want it to be.

A bit like PMPO....

Then again, if we were to high pass filter the input to say 10Hz (see Proprius spec), then with a unity DF at 4.5Hz calculated by output impedance alone, with the input considered, would then give a unity DF at roughly half that frequency, and the DF at other frequencies should therefore be twice that of what I suggested.

All ways of manipulating figures to look good to the unsuspecting...

All this will be swamped by cabinet/room interactions anyway.