I'm back. Thanks for the earlier responses.
Here are some fresh waterfall plots of my 4 x 15" IB in a very non-parallel 27' attic with multilevel floors, an open stairway in the floor. Ceilings, floor and 45 degree walls are all boarded.
Listening position no BFD:
Listening position with BFD including +16dB boost @ 20Hz 120/60.
Nearfield with BFD.
Any useful thoughts?
