Where to go after Bel Canto Ref1000MKII

Mapman, take into consideration that DF is already limited to about 100 by XO inductor (approx. 0.08ohm) in series with the woofer. You don't want to limit it any further but it might be hard to hear difference between DF=90.1 (with DF=1000 amp) and DF=83 (with DF=500 amp). It might be different with your speaker but it is worth checking IMHO.

Mapman, I'm also a happy owner of Icepowered amp (Rowland 102). I think that bass control is phenomenal but at the end it might be only difference with effective DF=100 to DF=50 (with DF=100 amp) and that is change of 100%.

Unless woofer has separate amplifier it most likely has inductor in series to attenuate high frequencies. You might find out what is resistance of this inductor to have general idea. In any case, if you have this inductor it will limit your DF more than amp. I wouldn't go lower than DF=200 amp, since my speakers, similar to yours, seem to benefit from tighter control. New Rowland 625, that looks very promising, has DF=200.

Damping factor in your Icepower amp drops with frequency getting to about DF=10 at 10kHz. It is the nature of the beast (class D amp) but it might be not important since tweeter's impedance increases with frequency.

Mapman, that would be the best, since speaker designer knows more about DF effects than anybody else.

Mapman, yes they are related since negative feedback lowers output impedance but class D has pretty low output impedance to start with since speaker is always connected to low impedance source (GND or V+) with Mosfets and only direction changes. What benefits our speakers might be not the best with other already over-damped speakers. With class D they often complain about loosing bass. It is also matter of personal taste. I like well defined bass, meaning short when it supposed to be short and long if it is recorded that way, but many people like round, loud bass all the time. One cannot argue with taste. I also noticed improvement in quality of the bass with more natural attack and decay - very pleasant with well recorded acoustic bass. It is possible that my amp and speakers just like each other. Negative feedback improves everything but increases Transient Intermodulation responsible for odd order harmonics and bright sound (overshoot in time domain). Here is example showing how feedback improves DF that I posted a while ago:

Let’s take amplifier that has gain of 30 (31.6dB). When input voltage is 1V output voltage is 30V. Output voltage drops (for whatever reason) 1V under 1A load to 29V. That's 1ohm output impedance (DF=8).

Now, let's build this amp with gain of 300 but feed 3% of the output voltage back to the input in opposite phase. As a result amplifier’s output is the same 30V as before but input is the difference between 1V and 3% of 30V = 0.1V Let’s verify (1V-0.03*30V)*300=30V

Let’s load this amplifier with 1A. Our voltage drop inside is still 1V under 1A load, but output voltage will be higher than 29V because we subtract less from the input. Output voltage will be 29.9V and output impedance will be 0.1V/1A=0.1ohm (DF=80). Let’s verify. (1V-0.03*29.9V)*300-1Vdrop=29.9V.

Output impedance dropped 10 times. Expression 1+B*Aol is known as “Improvement Factor”. In our case B (“Feedback Factor”) = 0.03 (3%), Aol (“Open Loop Gain”) = 300 thus Improvement Factor = 1+0.03*300=10.

Mapman, acoustic bass has very good bass definition, being long scale instrument, in comparison to bass guitar (unless slapped). If feel sorry for the guy who had to carry this instrument if my system cannot do it justice.