Mojo,
From my plots, there is a definite dip around 125Hz. It doesn't matter where I move my subs or mains. So I think your "hole" analysis may be warranted. If I remember, this dip also shows up on the Axiom M80 curves.
All,
Okay, I tried using the BFD to replicate this "punch". Using 62 Hz as the freq, I would say it sounded more muddy. There was some additional thump, but not much. I moved the frequency up to around 72 Hz, and it got worse. Then... I moved it down to 55Hz.
There was definitely a much more pronounced sense of punch. I raised the gain from +6 to +9 db, and it was even more pronounced.
Now, saying after all this... I'll give you my opinion of this addition. To me, it sounded like one of those cars passing down the street with the windows open driven by a 17 year old. That same resonating frequency that you feel as the car drives by, the one that seems to shake your fillings and drown out the actual music... That's the sound that was amplified at 56 Hz.
It certainly added a lot of punch to the music, but to me anyway, it sounded very artificial. I tried several genres of music (from Reggae, to pop, to classic rock), and both slow and fast music. As long as the frequency was in the mid 50 Hz range, there was a lot more punch with only a little added muddiness.
Having said that, it all comes down to what you like to hear. In my case, I immediately removed the filter. I did not really care for it. But, if this is what you are looking for, an EP350 with a BFD added to it may (imo) give you what you are looking for (for a hack of a lot less money).
