Squash balls

I'm making a basic TT isolation plinth using squash balls as the damping.
Is there a preferred hardness / softness to use? I'm thinking softer would be better, but would also compress permanently over time.
Or do I go for a medium and have done with it?
My TT isn't terribly heavy, so maybe the softer ones would do it?

Cheers..
 
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At the risk of throwing another variable into the mix: If your plinth/turntable isn't symmetrical (and most aren't) using the same balls on all 3 or 4 corners may result in things not being level.... You may want to use harder balls on the heavier side, to help level things out (say's the guy currently adjusting the spring stiffness on the three corners of his turntable, to level it out). Cheers, Dave
 

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I've used squash balls under loudspeakers with success. 1 1/4 inch plastic waste pipe cut into rings make an ideal support. As @Simon points out you will need to find the balance points for a turn table. Re other posts cork is too hard to provide the low frequency isolation you are looking for.
 
I've had another thought..

I've built the plinth and made it the same size as my tt plinth, and using 18mm ply I had left over.
It's ended up being quite tall and I'm not sure I like it.

I'm going to start over and I've ordered an 18" square piece of 2" thick memory foam.

I think this, sandwiched between 2 pieces of ply should do the trick.

Memory foam has the ideal damping qualities I feel. I don't know how much it will compress under the combined weight of the tt plus the 18mm ply but 2" hopefully should be enough.
 
You can use a small bike tyre tube between two plates. Inflated as you please. I saw this done by a guy who worked on nuclear medicine gear.
Eons ago (when I was in grad school), I had to isolate a laser interferometer rig from vibrations - much more sensitive than a turntable. After a bunch of experimentation, I put the setup on a piece of 3/4" particle board, with small inner tubes (I think they were meant for snow blower tires) underneath - the tubes were only partially inflated. This worked quite well.
 
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@mpeg2
waaaay back, I was about to do something similar for the computer rack at the company I worked for when, after we had already had a catastrophic disk crash, demolition of one of the neighbouring buildings (and subsequent new construction) promised shuddering floors going forward.
Never got the chance to implement it though. They moved instead and I left.
 
Memory foam stiffens as it compresses, poor choice.

Racquetballs are a good choice for upto 20kg. Though I use a 1" cross section" 26" inner tube under my kuzma. The benefit of an inner tube is you can inflate to the right pressure to affect spring rate and easily move it to affect balance/level.
 
Back in the dark ages when I had a turntable I used a base made from compressed fiber cement sheet with 25mm soft foam placed underneath. The foam was cut into squares and rectangles and positioned so the turntable was level but when pressed down and released it would bounce (oscillate) a couple times. A bit of trial and error but effective as you could hit the rack and the record would not skip.

Later I didn't need it as acquired a cheap Harksound by CEC turntable that had it's own internal suspension built into the base that consisted of springs with foam inside. Only cheap plastic construction but effective as you could tap the base with no ill effect on the record playing.
 
Sorbothane isolation pads would be even better than the silicone ones linked above, but they're more expensive.
IIRC, for any of these elastomer based isolation devices, the best result is when the weight of your turntable compresses each pad by a third. You probably can't calculate this, so buy something with a return policy, try it and then see if you need more or less based on how the first pads compress.
I agree that memory foam will stiffen under load and won't be a good solution.
 
going by the lack of compliance I saw on this guys isolation platform squash balls, tennis balls, sorbothane would not work. I now remember he said something similar is used to isolate electron microscopes, no doubt along the lines of what mpeg2 mentions.
 
The inner tube thing used to be fairly common. I remember one example where the owner finally settled on a marble slab on top of the tube, with the turntable on top of that and the pressure adjusted as required - quite soft I believe.