Here are the results of the FR after adding the Behringer.
The blue line is the sub without BFD, the pink line is after I added the Behringer. I may make a few more adjustments, wanted to get your thoughts on this response. looks very good from 16hz to 50hz, any thoughts on the decible drop between 50 to 80hz? Is that normal? this test was done with the sub only, no mains.