You should look at building a passive sub into the cabinet and amplify it exteranally. Use Liquid Nails on all screws when you put it together.
I had my sub on a brick fireplace 5" elevation and it sounded aweful (lack of energy) it was a VMP with a Slot loaded passive (probably part of the problem)
Another option
Chris
I had my sub on a brick fireplace 5" elevation and it sounded aweful (lack of energy) it was a VMP with a Slot loaded passive (probably part of the problem)
Another option
Chris