I thought I was the only crazy to do this. I sealed off my fireplace with expanding foam and carved out a nice shell and painted it flat black. The sub is down-firing and side ported. My firebox sits about 10" off the floor. It sounds great, and it's a great conversation piece. People look at my speakers and are in awe at how low they go. I just laugh. Plus, it hides an ugly big square box that clashes with the room. I say go for it if it works for them. Works for me.
