Best type of metal for turntable platform?

  If I were to machine a plinth, I’d choose Corian, rather than any metal.  

I would use the Panzerholtz, I prefer it of all.

Yes, I live in an old home, with ‘flexible’ floors as well. Had similar issues, and tried all types of things (which worked to some degree or another) before I got my SOTA Sapphire.

As I always say now, get a SOTA, problem solved 😉

But, first off, is your TT on the first floor with a basement below? Is the basement unfinished below the turntable? If so, a cheap way to add rigidity to the floor is to get a few 2x4’s, cut them to slightly more than from the top of your basement slab and bottom of your floor joists, locate then under the turntable area, and along a couple of floor joist spans, and use the 2x4’s to reinforce the area by simply hammering then tightly in place. If the 2x4’s bow a little, that’s fine, that means there is tension. No need to nail them to anything, simply friction fit.

Yea, technically you should use treated limber, but 2x4’s are cheap, so if they ever start deteriorating against the concrete, replace them. Unlikely to happen unless they are there for years.

You might still have to do more, but that is a great start if you can do it.

There's crawl space under my floor. SOTA has came up many times for my situation, but I do really like this TT and want to make it work. Even if I wall mount I feel that the flexible floor vibration will creep into the wall.

I even replaced the bottom of my whole BDI audio rack with 2 types antivibration pads (one rubber and one with cork) that are for washer/dryers and it really didnt do anything.

There’s crawl space under my floor. SOTA has came up many times for my situation, but I do really like this TT and want to make it work. Even if I wall mount I feel that the flexible floor vibration will creep into the wall.

Well, you could still do it, just not as easy. Dirt or gravel floor in the crawl? Or concrete? If dirt or gravel, you could get 12x12 concrete block as a simple ‘footer’ sitting on top the dirt or gravel, and then brace the 2x’s off of that.

Your problem is the floor joists were undersized for their span, or at the limit of acceptable design, which equals ‘bounce’. Not unusual in an older home. Fine for most folks, but not for most turntables, except the SOTA, of course. 😁

if you can brace the floor, your solution at the table will be greatly minimized.