none that I have noticed. Concrete floors and all. With nothing to absorb the sound, you can really feel the pressure waves. I am very happy with the sound quality. But again, This is my first venture into the higher food chain sound systems. With so much to pick from out there, I closed my eyes and threw a dart. Turned out Outlaw is the bulls-eye. I would have got Outlaw amps too but already had the one NAD.

Oh. That Cheyenne Mountain. I remeber that from my Civil Air Patrol days back in the 70's