[Mike P.]

The P.E. Bash 500 has a default HPF at 30 hz. By changing 2 resistors the frequency can be altered along with various amounts of boost at specific frequencies. The documentation is here:

http://www.parts-express.com/pdf/300-752.pdf

Her's a pic of the board that identifies the resistors:

 

[Mike P.]

You don't want to take the HPF off as that is what is what protects the sub from bottoming out at the lower frequencies. You choose the right one that gives you the most output from the sub without it exceeding Xmax. What model number is the Dayton sub? I post some modeling to show you.

 

[Mike P.]

EDIT: Wrong parameter entered. The graph has been redone with correct parameters.

Here is some modeling of the Dayton DVC385-88 15" in 7.5 cu.ft. sealed.

Yellow is what the amp has now, a HPF at 30 hz and 2 db of boost from 36-40 hz.
Green is a HPF at 20.7 hz and 1 db of boost from 31-35 hz. The lower HPF gives you slightly less output from 30 hz and up, but more output from 30 hz and down.

 

[Mike P.]

If this is for HT, with an Xmax of 15.1 mm, going ported would get the most out of the sub.
White - if you added two 4 inch ports 21 inches long each, HPF 18.7, 1 db of boost at 25-30 hz.

Yellow 94 db at 20 hz
Green 101 db at 20 hz
White 109 db at 20 hz