08-17-10: Azjake
Perhaps Steve or Albert would care to discuss the why 's and how's of they're respective plinth applications and what they feel it has achieved for them?
Azjake
The original SP10 Technics was released late 1969 or early 1970 and it operated with feet (no plinth) as Raul describes. Matshusta engineers found lack of stability and solidity of performance and from that point on offered later versions with increasingly massive plinths.
As for design, materials make a big difference. Technics in an attempt to add mass with beauty, designed the obsidian (volcanic glass) plinth which had a nice shape and was beautifully polished.
However, when Hi-Fi Choice reviewed it, they reported that the bass frequencies were lacking and there was a shallowness overall in the mid and upper mid frequency region.
Cause was reported to be from amorphous "structure" of volcanic glass and that other solid glass plinths and / or platters exhibit similar characteristic.
I agree with this British review, it's an accurate description of what I heard in my experiments. Noteworthy too, SAEC Japan (the wonderful tonearm builder) designed a massive, ultimate plinth for SP10 that is still sought after today.
If you dont believe material has an effect on the outcome of the plinth please consult data on density, sound propagation, stiffness and transfer. A good source to begin is:
The practising Scientist's Handbook, Alfred J. Moses.
(Van Nostrand Reinhold Company, New York, 1978).
Anyone who wants to try their Technics or other high torque direct drive table with slender footers and no mass are welcome to do so and report back their findings.