I was able to squeeze a filter and q switch into my Orion without enlarging the cavity. I had to move the pan control to hole where the bass control was. The filter and switch then fit in the two back holes. Its a tight fit, but it works. The switch is too small for the hole, so I put a small piece of plastic tubing over the switch as a spacer. I had a larger nut, but you could use a washer as well. I wasn't to hard to do, and it sounds great.