Feedback through turntable

You may find that seismic isolation can benefit airborne resonance issues too. Though only because it would allow the rest of the table to vibrate and dissipate the energy.. 

A cheap way to experiment is to use a small, partially inflated inner tube under the platform your TT is on. Simple and effective against some horizontal and many vertical vibrations. Though, if you've already ordered the springs, you may as well see how that goes.

@bdp24 ha, I had no idea. I have a teak cutting board on an inner tube.. 

Where did you get your roller bearings? I'd love to DIY, but I haven't found good cups.

That sounds like an amazing platform!

I tried a 2" maple butcher block on the innertube for under my rega, but it deadened the sound too much. The 1" teak seems to work better. 

I like the idea of recessed mounts..

I thought I could just do the math and buy springs with the correct specs, but trying to find a source will be the hard part. Hence my inquiry.

@slaw would you recommend springs instead? I'm not willing to drop a lot of coin, so switching to springs seems like something I'd be willing to try. Any recommendations?

@slaw never mind. I read your earlier posts and saw you mentioned machina dynamica. I'll check them out

Ah, got it. Right now my rega rests on a wooden plinth that is resting on a partially inflated inner tube on my credenza. Getting rid of rubber would mean I need a new method of vertical seismic isolation for the plinth. Hence my spring inquiry..

Also, my tube pre amp is on a wooden plinth on an inner tube. So I'll need some springs there too..

@slaw dude, chill. I’ve had a busy weekend and I just finished installing the springs on Thursday, so I’ve hardly had time to report back. I didn’t realize thread loyalty was a thing.

I bought some 2" compression springs with a spring rate of ~9lbs/inch from Grainger. I then drilled 4 holes in the bottom of my maple butcher block platform approximately 3/4" deep and installed the springs in the holes. To protect my furniture, I put cork discs under the springs.

I also finished mounting the tt motor on the butcher block. I still had the motor circuit board attached to the tt plinth, which made moving it a pain the ass.

So far I like the sound of the butcher block on springs better than on the inner tube. As far as leveling/ mass loading, my butcher block is 2" thick and plenty heavy, especially when the tt is on it. When I drilled the holes for the springs, i made sure they were as equal in đepth as possible. That, combined with the self leveling nature of springs has made leveling a non issue. I also thought of using three springs, but it was too wobbly when I tested it.

@miner42 thanks for starting this thread. I've definitely made some noticeable improvements with the info here. Good to hear (read) you're making progress too!

Geoff- I will say that I'd try little bowls if there was a believable explanation for how they work and what they do.. I'm not a total reductionist, so I don't shoot things down if they aren't ideas in the mainstream, but my mind does need something to go on, so I can figure out how to implement. Though I suppose it would be pointless since I can't imagine decorating my house with copper bowls.. My lovely wife let's me do what I want with the music room, but she wants input on the rest of the house

Geoff, sorry, got my threads mixed up!

@slaw.. you're funny, I like how particular you are. Yes, you are right, I do owe you thanks for bringing up the idea of springs. So thanks! 
Also for the idea of getting rid of rubber. That's where the wooden balls for rega feet idea stemmed from. I ended up doing that well before the springs and forgot that I got the idea from this thread.. I get them mixed up sometimes. 

So, how does it sound? 
Here are the changes I've made 'because' of this thread. They may not have been mentioned, but the ideas here got me thinking..
- removed 3/4" teak cutting board on inner tube used as iso platform, replaced with bigger 2" thick maple butcher block on inner tube. Sound became quieter, which, in the past I didn't like. But upon further analysis, the butcher block reduced feedback, which was why it was quieter. Recent upgrades in amps, PCs, SCs and ICs let me hear this difference more clearly.

Then I got rid of my rega rubber feet and used wooden balls in their place. I put a small piece of no slip carpet cushion under each ball to stop the turntable from sliding (a problem since my motor sits on the butcher block). This cleared up the sound. Mids and highs had better definition and more separation from each other and the bass. Oddly, this has resulted in a more coherent sense of music.

And finally, the springs. I replaced the inner tube with 4 springs from Grainger. They are ~9 lb/in rate. I tried three before I drilled counter sink holes, but the instability of three without being counter sunk led to a wobble that looked like the whole thing would fall over. So I never listened to just 3. Also, if I'd have wanted to go with 3, I'd have needed a higher spring rate, as the 3 were far to compressed.  Switching to springs has also improved sound clarity and has mostly led to better bass definition. It's cleaner and tighter.

Good stuff! 
Not suggested here, but removing the tt motor from the plinth and making a mount to put it on the butcher block made a YUGE improvement in sound too.

The no slip carpet padding is incredibly minimal, maybe 1-2 mm thick. Wooden coasters wouldn't work because they would slide too.. I need something non slip. I could sand small divots in the platform for the balls to rest in...

I'm on a ski vacation for the next week..

When I return, I may try sanding divots with a Dremel attachment...

Really though, the padding is BARELY there..

Here's a pic of the no slip pad.. I would hardly call it a pad.. http://philipbrunner.com/wp-content/uploads/2016/01/Ultra-Non-slip-Rug-Pad-4-x-6-P11996891.jpg

It's so satisfying to find the solution to a problem. Sounds like you're well on your way! Good luck and have fun with the rest of the isolation.