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How dose your plinth sound?

Iv been thinking about the materials that turntables are made out of and have a few questions. It seems that much of what is desirable is a material that will not resonate with what ever vibrations it is exposed to ie: floor, motor, styles and arm resonance ect. Yet many tables are made of materials that are very resonant ie: aluminum, glass, brass and.......wood. Wood can be very resonant depending on the type. This brings me to my questions. I see that the Teres is offered with different plinth materials, acrylic, plywood and solid wood(glued strips). It is also offered in different kinds of wood, cocobolo, jatoba, wengi and such. i cant help but think that the sonic signature between say ... acrylic and cocobolo is very different. When cut and shaped right cocobolo is a choice wood for marimbas, as is wangi. Acrylic just sounds like a dead chunk of plastic. Off the top of my head i would think that a wood like cocobolo would be a poor choice for a plinth or a platter(saw a picture) materiel. Teres wood plinths are laminated so this would cancel some of the natural resonance of solid piece but still. I will stop rambling on and just ask ..... what is the relationship between the plinth and the tables sound? If you had three acrylic platter Teres one with an acrylic plinth one with a cocobolo and one with a lead what would happen and why ........

Bill...
bkcme
twl
3,251 posts
 
In the Teres, the base is shot-loaded differently than the platter. There are large holes drilled cross-wize and capped with the final sections of cocobolo after filling.

The answer to your question about which vibrations are more important to control, is "all of them". All the platter vibrations, or as much as possible, should be dissipated or channeled through the spindle and bearing and plinth to ground. In the cartridge/arm combo, the same is true. Dissipate or channel through the plinth to ground.

During the Teres project and beyond, many materials were tested for plinth usage. So far the Cocobolo and lead shot top the list. For your "baseline", the denser the wood, the better the use for the plinth. Whatever vibrations do survive the wood, are to be dissipated as heat in the microscopic movement of the lead shot. The lead shot also adds the needed mass for augmenting this style of turntable. It would be horrible on a Linn. Different designs need different things to help them work.

You first need to understand what is involved in turntable design, before you can address what types of vibrations to control, and where and how to control them. Not all design parameters are applicable to every design.
edle
235 posts
 
The function of the plinth is simple. It has to resist/absorb vibration, both airborne and from the ground and from within(for turntable with stand alone motor then the vibration is from the bearing only).

And common sense tell us the heavier and denser the plinth, the better. Also avoid any turntable with an empty cravity inside the plinth!

I used all of the above points to design my DIYer turntable's plinth. The plinth that I have is about 55lbs total with about 18lbs of sand and 2lbs of lead shot filled fully inside the cravity of the plinth. I use lead shot because of its high density. And sand is a very good medium to absorb/turn mini vibration(vibration from bearing, air or ground) to friction and then become harmless heat.

It takes high mass/density to combat vibration both from the air and from the ground and lead/sand to destroy them.

As for Twl, may be you should built yourself a bigger, denser and heavier plinth with sand/lead shot mixture filling the cravity. It will for sure have better performance than the stock Teres plinth.

Cheers...............
twl
3,251 posts
 
Edle, I'm coupling my plinth with cones to a very heavy base with similar ideas you used in your plinth. The mass coupling to the base will provide similar results.

I'm glad you are DIYing with your TT. We need to see more of people like you, who are reaching out beyond the normal boundaries, and into the experimental world.
bkcme OP
8 posts
 
I realize that there are many variables in design and suspended is one that im not about to attack(build). In general im referring to the “slab o plinth” type of table. So if i understand right whether its a light or a heavy plinth the ideal material would be one that absorbs vibration without vibrating its self, and/ or transmits vibrations away from bering/ arm(one way) to another location?. Question ... can you induce sound to travel in one direction. Say with different layers of materiel with the most resonant being the farthest away(or some other arrangement)?
As for the mass issue i have a hard time believing that the “more mass is better “ argument. All mass is not created equal. Some would absorb and some would reject sound. I believe how you use the mass is the most important thing. Also a 300 lbs. turntable is not an option!(for me at least)...... On the other hand ... anybody know were i can get my hands on a few hundred lbs. of depleted uranium? .. ; ‘ ) ...
edle
235 posts
 
All we are dealing here is physic. Very simple.
It takes high mass and density to combat vibration.

Of all the best turntable available now, the Rockport is 600lbs, the Walker is 300lbs??!!!. And there is a reason behind it.

Yes, depleted uranium is probably the best material. But it is hard to find and you might get radiation sickness or cancer from it!!!

But if I can find a way to seal the plinth completely. I think mercury is the next best material......

Cheers.........
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