In Issue #34, I wrote about my studio's lack of floating floors, and how the Auralex GRAMMA isolation platform reduced the amount of bass-amp rumble escaping the main room. I also noted that the GRAMMA had an immediate and very discernable effect on the "tightness" of the sound coming from the bass amp. The GRAMMA utilizes two pieces of high-density PlatFoam to decouple what you place on it from the floor. This same PlatFoam can be purchased by itself in box quantities to float larger structures. 24 pieces of 4 ft long 2'' x 4'' strips come in a box of PlatFoam, along with three tubes of TubeTak adhesive, enough to support an8ftx8ftarea.
Loving the positive effects of the GRAMMA in my studio, I decided to build a 6 ft x 8 ft drum platform for my live room using a box of PlatFoam, 3/4'' subfloor plywood, 2''x 4'' runners, drywall screws, and a tightly woven rug. (Runners or sleepers aren't normally required-I used the runners to solidify the grooved joint between the subfloor pieces that make up my 6 ft deep platform. My runners don't touch the floor, only the PlatFoam does.) Design goals? Quick build, stable, passable through doorway... and of course, less drum sound making its way out of the studio. Once I'd collected the materials, it took me four hours to build the drum platform by myself.
First my comments in regards to construction. The PlatFoam strips vary in thickness by up to 2 mm. Even with the strips glued six inches apart center-to-center, that variance is enough to make a platform constructed of a single layer of plywood bouncy/flexy. I'd recommend using two layers of plywood glued and screwed together to prevent flex. TubeTak will hold foam onto wood tenaciously, but its immediate stickiness gives you a false impression that the adhesive has already set. The foam will pull away if you try to position your platform before full curing has actually completed. Wait at least 24 hours. Auralex recommends using an electric carving knife to cut their foam. I obtained good results using a hot-wire foam cutter.
My comments in regards to acoustic benefits? I'll make this short. The difference is much bigger than I anticipated. Especially for the "khoof" of the kick drum and the "pwack" of the snare drum-I hear less of them outside of the tracking room. And unexpectedly, I hear much less bleed of the drums in the guitar and bass amp mics. Apparently, a good deal of the drum bleed was being transmitted through solids: across the floor, through the mic stands, and into the mics. The PlatFoam-floated drum platform reduced this thru-solid transmission significantly. Less bleed, more focus, better drum sounds. Design goals accomplished... and then some.