riser construction

My house is being built and I am having a dedicated theater/game room. After all the research and searching this forum, I am still not sure what the best route is for the riser.


Here is my plan after some research and hopefully someone will be able to make sure this is correct to allow the best sound on the riser and throughout the room.


I am having a 10" rise and will be about 6'x10'.

I was planning on floating the riser with rubber pads and drill 2" holes in front of the riser between each joist of the riser (read this somewhere and was recomended, not sure why?). I was then going to lay 6 mil clear plastic down either between the joists or on the floor and build the riser on top of the plastic. I would then staple the plastic on the sides of the joist or inside perimiter about a 1/3 of the way up. The plastic is to keep the insulation fibers (I will stuffing it with insualtion 3/4's the way up) from leaking out under the riser since it is floating. Then I would use 2 layers of mdf for the top. Then I would carpet and trim on the bottom to hide the rubber bushings giving it the appearance of a flush look to the floor.


Now my next question, why the holes and rubber bushings? Is this to allow the riser to move and shake at low frequecy. Giving the people sitting on the riser a better feel of the LF? or are there other reasons? Do I need the holes and should I float the riser?


Thanks, Coop