Can't say I've ever heard of this problem, but if your subwoofer response is satisfactory with the BFD bypassed, why not just take it out of your system?
Perhaps, but being a frequency plot, there are time domain phenomena the graph would show...Graph don't lie, right?
How did you initially setup your phase?OK I have done some more tests..
without the DSP1124, the null happens at phase 0
with the DSP1124, the null is at phase 180 (bypass mode), so it is indeed flipped around 180.
It would seem I should leave it at phase 0 then. However after equalizing I get no null only if I leave the knob at 180, so there it is. Once I leave 180 the null gets bigger and deeper.
So that is the final setting.