Skeletal vs Plinth style turntables

My 2 cents worth.

IMO a perfect TT needs to satisfy three criteria.
1) Perfect DYNAMIC speed stability. No drive system meets this and passing the (in)famous timeline test is zero guarantee of dynamic speed accuracy, only average speed accuracy.
2) Perfect dynamic dimensional stability. Impossible unfortunately. My view is that a skeletal design makes this goal more difficult to achieve since we are introducing the support structure, shelf, platform, into the equation. It effectively becomes the plinth. Related to this is the minimisation of joints and material changes in the platter-arm loop.
3) Perfect stillness. Again impossible, but careful choice of materials and correct implementation of single point mechanical grounding or isolation, would likely be advantageous. This too suggests that a skeletal design is not optimal.

A heavy, inert, one piece plinth is indicated if you agree with goals 2) and 3).
I will not open Pandora's box with any comments about goal 1).

Propagation speeds of the materials chosen also need consideration.

Hello Richard - thanks for your contribution as I know that you've probably forgot more than most people know about decks. Most of the 1970's DD's of yore seemed to all consistently have heavy plinths. The decks having been designed at the height of vinyl when the multinational companies really threw all their resources at turntables - so they probably knew a thing or 2 I guess.
Not being funny when I say this, but I also consider the SME range of decks a skeletal design - albeit with high mass. I personally quite like the idea of combining reasonable mass, intelligent damping, and suspension.
I have read around, and some people take just one concept, be it mass, suspension, a single tasty material - and then they use it to the absolute extreme thinking it is the be all and end all. By way of developing my point if mass alone were the way forward then one would fix a turntable into the stonework of their homes.
I am going to have to read a bit more on propogation - in laymans terms does that relate to how a material in fact transmits, or absorbs a given vibration or sound?

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