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Regarding has2be's statement that screwing the two pieces of birch ply together will defeat the isolation provided by the constrained layer damping placed between them, that layer of damping material is put there not to provide isolation for the turntable, but to absorb and dissipate the resonances of the plywood itself. Green Glue, ASC Wall Damp, and EAR Isodamp is too thin to provide any isolation. It is the springs, roller bearings, Herbies feet, or Seismic Pods (or even slightly inflated inner tube) placed under the shelf that provides isolation, not the constrained layer damping.
Yes that is what the layer is there for, no question. However, the screws still allow the resonance to travel straight "through" the absorbing layer from one ply to the other ply....., it stands to reason . I know the concept well, and its intended purpose and the screws will and do defeat the performance of impeding those resonances. There are adhesives out there that defeat the problem you create by not using an adhesive that will act as you require it to as well.... |
Good point had2be, one that had not occurred to me. I have Solid Steel racks, which unfortunately have 3/4" MDF shelves (yuck!). I bought extra top shelves to double the thickness (for my fairly heavy turntables), as well as ASC Wall Damp cut to the size of the shelves, but haven't added them yet. I'll eventually replace them with BB ply. But no screws! ;-) |
Thanks again for the excellent replies everyone,
I’ve been looking at maple blocks on Amazon including the Butcher Block Acoustics one mentioned. Prices seem reasonable and I already have some spikes. What is too thin for the block to be effective enough? I’m looking at 1.75" ones and the 3" BBA one. Is Maple the main choice as I see Walnut for more?
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Go as thick as you can on the wood. Not all butcher block is the same. Don't write off granite so easily, especially if you like detail retrieval, air, and tight clean bass. You could sit the granite on felt pads.
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asahitoro, even if you go with maple or butcher block, consider getting two pieces and placing a thin sheet of constrained layer damping of your choice between them. That will mitigate the resonance found in all materials, including wood. Actually, especially wood---that's why they make drums and guitars out of it! Another thing to do is put the grain of the wood in the two pieces 90 degrees opposed to each other; one with the grain front-to-back, the other side-to-side. That will increase the stiffness of the assembled shelf. |
