I was a Noise and Vibration research engineer working on ways of making the record players more accurate but still economically to make.
Wow, Frank, I wish I could have tapped your knowledge when I was building an isolation platform for my "high end" turntable. (The turntable being a fairly over-built 55 lbs of aluminum, belt-driven, affair).
I'm not a tweak-believer by nature, but given the fact turntables work on the principle of amplifying minute vibrations, it did seem to make sense to minimize spurious vibrations, which is why competent turntable manufacturers endeavour to do just that in their designs.
At the very least I had the issue of putting my new turntable on an existing somewhat flimsy small rack (the only one that would easily fit where it needed to go), which sat upon a springy main room floor of an old house. It was very easy to feel vibration getting to the turntable when someone walked on the floor.
I researched what other people did in isolating their turntable, but I did so with skepticism feeling it was hard to untangle valid concerns and methods from audiophile myth and exaggeration. And being no expert on the subject, I just did my best to filter obvious nonsense, and try out things that made sense. I used a nice seismometer vibration measuring app on my iphone and ipad to measure the relative isolation characteristics of a whole bunch of materials, footers etc. By far the biggest gain, both in terms of feeling a reduction in transfer of vibrations, and in measuring with the app, came from a spring-based isolation footer.
In the end, since I had ordered to test a variety of solutions, I sort of used them any way and threw some stuff together. I ended up with this:
The turntable now sits on a 2 1/2 maple block (desired as much for the beautiful finish and look, as for isolation), under that a layer of 1" and 1/2" MDF bonded together by wall damping material, which then sits on a layer of steel (1/8" I think), which finally is held aloft from the rack by 4 spring-based pods.
I'm quite sure that is overkill. But it was fun and nonetheless the results seem very good. If I put my hand on the top shelf of the equipment rack - beneath the isolation platform - and rap on the rack, or stomp on the floor, serious vibration is easily felt through the rack. If I put my hand on the isolation base and do the same, I feel virtually nothing transmitting. Same with using the vibration measuring app. Placed on the rack shelves, stomping reveals large ringing spikes of vibration getting through. Placed on the isolation base...nothing.
So, that scratched my mental itch regarding isolating from floor or wall-born vibration. (We also have an airconditioner on the other side of the wall which can vibrate the area).
So my questions to you is:
1. Do you think any of this was actually worthwhile to do?
Secondly:
2. The above steps were mainly concerned with isolating external vibrations getting to the turntable. But what about any steps available for minimizing vibration created by the turntable system itself? I understand that turntable manufacturers take steps to minimize the influence of any motor noise/vibrations etc within the turntable design. But are there good and bad ideas in terms of helping "calm" internally-borne vibrations in a turntable? I imagine that a turntable placed on a sufficiently springy surface may exacerbate or amplify vibrations in the turntable. And from this wonder if certain strategies make sense in minimizing (draining?) internally-born vibrations - e.g. a turntable like mine his it's own aluminum cone footers that are conical to a spike. But whether softer footers of some sort might absorb spurious vibration from the turntable any better?
Thanks.