So the 20hz signal barrier is actually a high pass? How have you validated this?Not only is there no control of signal under 20hz, but you cannot defeat or bypass the 20hz highpass filter. Dayton squashing my hair tricks before they even get started. The best you can do is set it to 6db/octave.
Edit: I don’t use a high pass filter at all on my signal to my sub amp. But assuming that’s how the Dayton processes the signal cutoff at 20hz. Wouldn’t be better to apply a shelf filter? Have you verified in a scope with 20hz? I’m curious...