Yes. Quite a few active subwoofers use or have used this technique for decades (one pioneering company is Ace-bass, see their 1978 AES paper https://www.statco.it/Docs/AES 1978 Stahl_ACE_Brevetto.pdf), and some active multiway speaker also have amps with non-zero output impedance which maybe partially negative at low frequencies but then returning to zero or more likely larger positive values at higher frequencies because that is what most woofer and midwoofers work best with.
Post #6 shows the opposite.
Tweeter at 12kHz is no territory for electrical damping. The example was badly chosen.
Yes a maybe not obvious point to add here. If you increase the overall damping factor by modification of the driver then you automatically increase its rise time too - you can see that from a step response of the raw driver/cabinet.
If the increased damping has changed the "raw" frequency response then of course the step response changes accordingly. But if you EQ to the same driver terminal voltage vs frequency, step response is the same -- as it must be, despite the different damping.
When used to remove excess phase like from any classic XO, then yes.
Do you know of any studies on the audibility of pre-ringing? I know from studio work that is audible, that's without question, but I don't know of any decent guidelines.
This study is pretty convincing to me
I'm not aware of studies that look at linear-phase vs minimum-phase high-pass functions at very low frequencies (like well below 100Hz) but I did my own little private research.
I think it's called preringing solely because of the time domain measurements used to diagnose the issue. The sound in higher frequency transients with linear phase EQ (I've never heard it with crossovers specifically) is like a noisy, flanging, reversed version of the original.
Is the waveform of the woofer SPL or the electrical signal at the FIR filter output?
Its because there is some signal occurring before the main impulse - the amplitude of which depends upon the roll-off rate of the filter. Brick wall filters are an extreme case which are used often as an example of pre-ringing from the ideal filter, but the acoustic pre-ringing, the SPL, is nothing like this in a practical case. To flatten the amplitude and keep the phase constant within a woofer intended pass band would take many hundreds (possibly a thousand or so) of FIR filter taps and that results in too much delay in the filter (100’s of milli-seconds), so designers compromise and accept less than flat amplitude and less that constant group delay at the expense of filter delay, but reap the benefits “bass punch” improvements from improving the group delay. Engineering is always about compromise. From what I have seen on audio forums, the topic is often misunderstood.
It shows the acoustical target. The FIR output is that of a time-reversed allpass with the same phase response as the 6th-order highpass so the combination has net zero phase.
A synthetic signal to test the effect of linear-phase bass roll-off, you mean?
I tend to agree. The Horbach-Keele type is maybe the most prominent case that uses infinitely steep final roll-off. But the transition region still is quite wide and rounded, reducing ringing.
There seems no denying that, by two of the giants who's shoulders we still stand on today, no less.
Most likely perceptive bias. You simply cannot separate this from uncontrolled sighted listening.
Why do you think perceptive bias can't create explicitly noticeable differences? It is very capable of doing so - unlike the levels of distortion created by modern well measuring amps. In fact I would revers your statement. "This was too explicitly noticable to be distortion - more likely to be bias"
