Best type of metal for turntable platform?


I have someone that owns a CNC machine. And machine for me a metal platform to the dimensions of 16 x 13 x 3. Ive heard aluminum is a good metal vs price for vibration reduction. Does anyone have any recommendations? Any input would help. Thanks. 
deanshias
@clearthinker

Rolls Royce solution: Take up the floor, dig out a bit if required, lay new DPC, in-fill with concrete screed, lower floor level to get more ceiling height if desired. According to taste, re-lay boards except where equipment and speakers are to stand. Or lay carpet.
OK there is a cost, but it will be worth it.

As I have stated, you can get the same results for much less, simply by reinforcing the floor joists in the area of the table. In fact, I would never do what you suggest without doing so first, because you are adding more weight to a poor situation. Again, this is not unusual in wood framed floor houses, both old and new. Renovations and remodeling is my business, and sometimes need to do this to clients homes, and not for audio reasons.

Let’s take an exaggeration; if your turntable is sitting on a trampoline, which you will also walk upon while using it, how much will you spend for a platform to remove the effect of the trampoline? That is allowing the ‘tail to wag the dog’. First, get rid of the trampoline, then see what you might need, if anything.

I did this in my house before getting the SOTA. I had a few 2x4’s left over from a recent renovation project, used about 3-4 to support the floor beneath by rack. Took maybe an hour. I could then walk, jump, etc. next to my rack which minimized floor fall issues to a great degree. I think we can make simple solutions and over-complicate them, and make them cost more than necessary.


@antinn , said it pretty well. You will not isolated the turntable from anything with whatever material you choose. You could actually make things worse. Sometimes a wall shelf will help, sometimes not. You have to isolate the turntable from everything about three Hz. Including the dump truck that just drove down the road. You can feel it even on a concrete  slab. The only sure fire way to do this is with a suspended turntable tune to less than 3 Hz preferably by hanging. SOTA and SME are the best at this. Sota's may look simple but they are very well made and very durable. You can also choose the wood if you like. For $10,000 you can have a perfectly suspended table with vacuum clamping, a magnetic thrust bearing, Top notch speed control and a dust cover to boot. Many of these feathers are available in less expensive table. 
There are many spring loaded devices on the market. I the dealer does not ask you for the weight of the table as it plays with recodes an clamps, forget it, move on. The springs have to be tuned to the weight of the turntable and you always go with the lightest spring that will work. 3 Hz. That is what you are looking for. Then you can kiss foot fall problems goodbye.
I would do some homework on damping properties of different materials. There is a name for it, which I forget. You can use two different materials with a damping material in between. Or look at the plinth of the VPI Prime Signature - looks like its aluminum in between two other materials. 

I to live in a very old house with bouncy floors.In my secondary system I have an old Sota on a walnut turntable platform that utilizes rubber balls. When someone walks into this room the stylus  skips. In my main system I have a VPI Classic 3 on a 4 inch thick maple butcher block platform with 4 rubber and cork anti vibration pads. I never have any skipping and can even rap on the rack without any issues. The vibration pads are the same ones that are used in the HVAC industry. These pads are very inexpensive and you will find that the same pads are being sold under some audiophile brand names priced at 10 times their actual cost!
As far as metal goes the one material that has been in use for machine tools for decades is a special grade of cast iron called Meehanite. It's known for it's superior damping quality's , very important when designing a machine tool. The last thing that a machine tool needs to do is vibrate or ring, it wouldn't work very well.
I do believe it has been used before in a TT plinth, not sure who it was though.
If your going to use aluminum, maybe check out cast tooling plate. Being cast instead of wrought it should offer better damping characteristics. It's offered in many thicknesses and comes in a machined finish on both sides. It's cut to size using large CNC circular saws.

BillWojo
They are $1500 but an incredible upgrade for a TT-Silent Running Audio. VR platform. I put one under mine and the improvement in sound was the biggest change in my system short of upgrading my speakers from $10K ones to $30K ones!
SRA has two separate companies that make vibration control devices for the military and medical. Submarines and CATs!
It is clear, with over 40 patents, SRA devices allow complex machines and components to function as they were designed.
@bjw54

I have an old Sota on a walnut turntable platform that utilizes rubber balls.

I’m a bit confused. What SOTA table do you have? And why do you have an internally suspended table (with springs, if that is what it is) on a separate base? That would seem to defeat the internal SOTA suspension system.

My SOTA sits atop my rack, all by itself, and I can walk, jump, yell at, and bang on my SOTA Sapphire TT’s plinth, and it is not effected, by anything. Perhaps a bomb going on within the room might.....might. 😁
If you need vibration reduction you want an isolated wood not metal under a turntable but if you want to you should use brass as a metal nothing else.but a thick wood shelf about 2 to 4 inches thick of laminated wood like a butcher block will work best.
I would try a sandwich of Acrylic, Aluminum, and MDF to vary the density of  the materials.  A liberal application of silicone caulking between them.
I have a Townshend seismic platform (it has pods attached under it) under my turntable. When installed, it improved the sound so much I was incredulous. Unfortunately, the very low waves from the pods combined with my suspended floor and extremely light turntable created footfalls that didn't exist before (to anywhere near that degree). 

It was either live with the improvement and tread lightly or go back to square 1. I was going to live with both because of the sublime sound. But, guess what - I put in a wall shelf ($179 from Project) and put the Townshend platform on top of that. All problems solved and the sound improvement had to be heard to be believed. I was very skeptical.

I like the platform better than the individual pods because there is no fiddling around with placement. You can adjust the springiness in each spring to level the platform for items that have lumpy weight distribution.

@millercarbon takes a lot of abuse from some posters, but I have to thank him for turning me on to Townshend. I had the privilege of talking to Max himself a couple times - extremely nice down to earth guy, very honest - kind of like a mad scientist who does his own research and has solutions that work. When he starts talking about continuous earthquakes, he is on to something.
Wall mount, better shelving/ rack- 
better table, feet - so many options , solutions 
Many May cost less than suggestions so far-
Have had problems w “footfall vibrations “
Better turntable, racks, footers, cartridges, have helped for different situations.
From my perspective, no one size fits all
Of course not. But I think SME tables take care of everything (no shelves, pods/platforms, etc.,) from what I've heard. Not inexpensive though...Sound like an end game for the whole source discussion.


Given that you can have your own platter machined you should do the following:  It should have a hollow space underneath.  Think Technics SL1200 platter.  It has a flat top (of course), and then at the edges it has a lip (with all those dots).  Underneath is a rubber underlay.  Do something similar but rather than a rubber underlay you will pour epoxy (g-flex is good).  This will damp the platter.  This is important if you are having a metal platter, otherwise it will ring like a bell.  The constrained layer damping suggestions are also good.

As regards footfall I have two suggestions.  First add some mass.  For example I use a one inch slab of granite on my shelf.  Second get some aftermarket footers.  There are maglev footers on ebay,  Even better are Isonoe footers - they are in effect mini trampolines.  I can jump up and down next to my TT without adverse effect.
andrei_nz

Thanks for the info. Everyone on here has been very helpful. Do you know where maybe I cant find an exact schematic? I know that's asking for too much. He's the type that just needs the measurements and/or plans. 

Its puzzling to me how mini trampoline footers like the Isonoe can can be good for footfall.. I am intrigued though and might try them.  Once it warms up here, from influence of these replays, Im going to get under my floor and add supports to the floor. BUT! If I can find a way out of it.. Ill try it (without breaking the bank).
The floor supports will do the most if you can pull that off. I couldn't so had to do the wall shelf/platform I mentioned above. Your sound will improve dramatically when you remove all the vibrations!
The best by far is SYMPOSIUM ULTRA STEALTH EDITION this will give the best sound and isolation as well.Jump on on ASAP!!
So I decided on purchasing a Townshend Seismic Platform. Then when it warms up here im going under my floor in the crawl space and going to add supports to the floor. Then I'll ask my buddy to mill the platform.