Layer 1: Closed Cell Neoprene

With the resonant head facing down, the first layer of "stuffing" is a 1/4" thick closed cell neoprene rubber sheet cut to the inside diameter of the shell. I got this idea from the Boom Theory patent which states that this layer will kill false triggering from airborne sound waves picked up by the resonant side head.  I cut the disc out from a 20-1/2" x 35" x 1/4" sheet of neoprene that I bought from http://www.foamandupholstery.com/ for $6.95 (plus $6.75 shipping) .

Layers 2-5: Poly-foam

Next 4 layers are 2" thick poly-foam discs that are just a hair larger than the inside diameter of the shell.  I purchased these sheets of poly-foam from Michael's Crafts Stores. They came in 22"x22"x2" squares and I purchased 5 of them for $6 a piece.  I cut the 20" discs using an electric carving knife and a template that I made out of a sheet of 1/8" MDF.  Spray the carving knife with a bit of silicone lube, and it will cut the poly-foam like butter.

The bottom 4 layers of poly-foam are just stacked on top of each other and held in place by friction between the shell and lug screws as well as the tension between the batter and resonant heads.

I cut a slit in the fourth layer of poly-foam to make space for the jack cable.  I figure the poly-foam will also hold the cable in place and dampen some of the vibrations transferred by the cable.

Layers 6&7: Poly-foam

The last two layers of poly-foam were actually cut from one sheet. The discs are 15" in diameter with a section cutout to leave clearance for the sensor assembly.  The last three layers are attached together by double sided carpet tape between the layers to keep the smaller discs positioned in the center of the base drum cavity to preserve the gap between the foam and the shell.  The gap is designed to isolate the mesh head dampening layers of foam from the shell.

Trigger System

The trigger is a 35mm piezo sandwiched between two foam discs and is based on Cliff's "Top-Hat" and Bill's LogizmO.  The bottom foam disc is 1/2" thick closed cell neoprene and the top foam disc is 1/4" thick PORON.  The piezo sandwich is sitting on top of a 1/4" thick acrylic platform.  The Acrylic platform is supported at each corner by 1/4" thick Sorbothane mounting blocks that are glued to the the platform with devcon's flexible super-glue.  The other side of the sorbothane blocks are glued to a larger 1/4" acrylic sheet that is in turn glued to an aluminum angle iron bracket.  I know it is quite a few layers, but it gave me the right distance from the head and also gives good isolation from the shell.  I bought the Sorbothane and PORON from McMaster-Carr -- I actually used scraps leftover from my tom conversions.  I bought the Acrylic Sheets from TAP Plastics -- again these were leftover scraps from my tom conversions.

The aluminum angle iron spans across two Stanley L-Brackets that are mounted to the top two lugs using bonded rubber isolation washers.  The angle iron is fastened to the L-Brackets with four rubber well-nuts that expand when tightened.

Complete Assembly Without Mesh Head

Here is a picture of the completed drum with the batter head off.  The trigger assembly is mounted on the top side of the drum and the foam is sandwiched between the two heads.

Complete Assembly With Mesh Head Installed

This picture is shot with the head on, but with enough of flash to penetrate the mesh head and reflect off of the white poly-foam to make the head look slightly transparent.  The red circle shows where the trigger is, and the red dotted line shows the top of the foam dampening discs. The evans beater pad shows where my beater impacts the head.