Skeletal vs Plinth style turntables

GrooveMaster Vintage Direct

Above is our take on it

Good Listening

Peter

Parrotbee.
I think that good inspiration can be found if we look at how cutting lathes are constructed or outside of the industry, we can look at how milling machines are put together. These devices are required to hold a fixture precisely in place relative to the work piece, (record blank or machined material), whilst being dynamically loaded. This is exactly what a TT is asked to do.

No issue at all with a suspension if the siting of the TT dictates. My installation is basically fixed to the concrete floor and mother earth and I believe that this approach yields good results. Of course in most situations this technique cannot be used, so a suspension is a good solution.

Interesting re the SME's, ok you can see their entrails but their is a single structure carrying the platter bearing and the arm. In this respect they are pretty conventional.
However the box that encloses it all is missing. This is likely a good thing.

Damping is a real can of worms. It's use can yield fantastic results or it can suck the life out of the sound faster than a death eater in a Harry Potter Movie.

propagation speeds.

Yes in this case transmission velocity of sound thru the material.

for example: acrylic is around 2700m/s
copper is around 4600m/s

Hi Richard
I said the SME's are skeletal on the basis that they are quite open as you observed. I must say I do quite like SME's. My problem with the double deck turntables is that dust can gather - however clean your room -trust me I have one such deck.
I have in mind the use of adjustable oil filled motion control dampers (used for microscopes) and heavy elastomer springs. It will hopefully allow me tune the deck but not be too springy or overdamped.
Who knows maybe I can rope some local gonners into doing some listening tests at my home...

Here is the issue in mechanical engineering terms. It is not a lot different from the steering and suspension of a car.

In a nut shell:

the plane of the platter must be consistent with the plane of the cartridge. As the arm moves the cartridge must remain in this plane. Since the platter must revolve, there can be no slop in the bearing such that the platter can deviate from said plane.

As the arm must be set at a fixed point, it can then be seen that if there is any difference that occurs between the point of the arm and the surface of the platter that is will manifest as a coloration of some sort.

For this reason, the coupling between the surface of the platter and the locus of the cartridge cannot have any slop of any sort. To this end, the coupling between the bearing and the base of the arm must be as precise and tight as possible; IOW of a singe piece which will not respond to vibration, as if any differences can occur they will be interpreted by the pickup as coloration.

What this means is the more dead and the more rigid the plinth is, which also holds both the arm and the platter, the better the 'table will sound.

Parrotbee
I look forward to you posting pics of your creation. Good luck with the project. Also can you advise more details on the microscope isolators?

Atmasphere
Dimensional stability.... You said it far better than I

Thanks