Placing the Riser on a Slab Floor

[TCinGA]

Is there any need to use an isolation system (like Auralex U -Boats) under the riser? This is a basement room on a concrete slab.

Planning on using 2x10's for the riser, building the frame work and filling it with insulation, then a double layer of MDF wood for the floor.

Should the two layers of flooring be glued or just held with screws ?

[Anthony]

You can isolate it, but if the rest of the floor is not isolated, that may just be more cost. usually the isolation helps in floor absorption when on a slab, since the bass waves can't just pass through to the level below. But again, no harm. My riser is not isolated and it is on the slab. The rest of the floor is just a big area rug with a thick pad. Not ideal, but I didn't have much choice.

I have two layers on mine, but of plywood, which I would recommend over MDF. The edges of MDF chip under heavy use and even carpeted, they could break down over time.

Mine is screwed down so that I can get under there to run wires, if needed. That's come up twice. If it's more permanent, I would glue and screw, but be forewarned, you may have to destroy it if you need in there.

[John Simpson]

From what I understand, you need to avoid the riser becoming a resonance chamber -- one of our members filled his with sand, and another has stuffed it with old newspapers (not sure about the fire risk there).

To avoid any rattles or squeaks, Green Glue would be a good idea... although again, this is being fairly pedantic. Don't attempt to isolate it from the slab, as there's really no point.

[salvasol]

I place mine over the concrete slab too ... no isolation used.

But if you want to isolate the riser from floor ... I read that some people have used pieces of ruber tubes (same that is used for car radiators I think ); or if you want you can use this http://www.smarthome.com/8257FI.html ...