I have laminate over plywood over dimpled subfloor over concrete, and I had no problems with my down-firing ChaseHT SS-18.1 subs.
A few months after I got the SS-18.1s, I placed a 21" x 21" foam mat (like the ones below) under each sub:
- to see if the sound would be affected/altered; and
- to stop the subs from sliding around (I had temporarily stuck felt pads under the feet, and the subs would move a bit after some heavy demo-ing :gulp: ).
The sound didn't change, and the subs don't move around anymore. :bigsmile:
I wonder if the plywood and dimpled subfloor reduce the vibration of the laminate more so than I will get with just a 1/16" pad between the laminate and concrete. The foam mat underneath should help some. It seems if a downfiring sub makes the floor vibrate that a front firing one would also.
Brian at Rythmik discourages downfiring over laminate, I assume because it affects the sound rather than the fact that the floor vibrating would annoy a person.