Help! Tweaking My Lovan Rack for new Big A**ed Transrotor Turntable!

To isolate a turntable/arm/cartridge from higher frequencies (above about 10Hz) is easy; a suspended table does that very effectively by having mere springs acting as a mechanical filter. In contrast, very low frequencies "get through" the suspension---most table’s mechanic filters are effective down to only 10Hz or so. That is why seismic-frequency isolation is required by LP players for ultimate performance.

All kinds of material have been tried as very low-frequency mechanical filters---Sorbothane, Navcom, garden-variety rubber. Also cones and spikes of various sizes and shapes. Both of these do act as a mechanical low-pass filter, but their "corner" frequency is too high, rolling off rapidly also at about 10Hz.

The latest attempt to achieve isolation at low cost is with roller bearings---a ball bearing in a shallow cup. As very low frequency energy (vibrations) encounter the bearings upon which the table sits, they dissipate that energy by the ball bearing trying, in response to the wave of energy (vibrations travel through matter as a wave does in the ocean), to climb up the side of the bowl in which it sits. The energy, rather than being transmitted into the table/arm/cartridge, is turned into heat and dissipated by the bearing. Ingenious! Unfortunately, the roller bearing works that way in all planes but the lateral. In the lateral plane the roller bearing behaves just as do cones and spikes---not as an isolator, but as a coupler. If you add a lateral isolator---an air or metal "spring" of some sort---that is effective to as low a frequency as possible, then you can achieve good isolation.

Or, you can spend the $ necessary to get one of the electron microscope isolation table available, which start at around $2000. There is a third alternative, priced between the two, closer to the cheap side---the Townshend Audio Seismic Pods, which have been mentioned and discussed here lately. About $375 for a set of four when bought from England. Look on You Tube for videos of Max Townshend explaining their design and demonstrating their effectiveness.

ASC (Acoustic Science Corp.) offers a product named Wall Damp. It comes in 4" squares (I believe) and long strips, and was designed to act as constrained layer damping when installed between layers of sheetrock. I recently heard it's effectiveness (in Audiogon member folkfreak's music room), which is fantastic! Art Noxon states that the huge 4' x 8' sheets of drywall, when confronted with sound waves and other vibrations, behave as do drumheads when struck---bend, bow, and flex, creating an audible resonance. Rap your walls with your knuckles---they make a clearly audible sound, not a good thing. Folkfreak's walls sounded like slate when I rapped them! Wall resonance is a commonly-overlooked characteristic of the acoustic behavior of listening rooms imo---the final frontier! 

ASC sells the scraps and end pieces from Wall Damp installations by the lb., for real cheap. I just bought a lb., plenty for putting between 1- the two pieces of acrylic (or one of acrylic, one of aluminum; I haven't yet decided) that make up the pickup-arm mounting board of my newly-acquired turntable, and 2- the two 3/4" layers of my table's shelf. I will bolt or screw the two together, with a layer of Wall Damp between them. Sounds promising, ay? I can't see a downside, in theory at least.

prof, you’ve discovered and proven the "secret" of mass-on-springs isolation: you want the weight of the mass on the springs to be as close to the spring’s capacity as possible, without going over it. Townshend offers the Pods in different models with spring rates in much finer graduations than does IsoAcoustics in their Gaia line of isolators.

I too am not overly impressed with the IsoAcoustics rubber pods (rubber is rubber!), and am sticking with the Townshend Seismic products. I have only one set so far, 3 of the "A" version (maximum capacity 27 lbs.) under my 27 lb. turntable/arm/cartridge.