Best TT plinth material, cost no object

So, Ken, why isn't that project finished and what might you not like about the behemoth you built? Maybe that could lead you in a good direction. None of us have your skills in the first place. Many latter day belt-drive tables have virtually done away with a formal plinth and sound great. It seems based on word of mouth that idler- and direct-drive turntables do benefit greatly from a heavy, dense plinth intimately coupled to the motor/bearing. (But there are guys who like the Technics SP10 sans any formal plinth.) My own experiences with slate are in agreement with the idea that slate is very very good. (I have now made or had made slate plinths for Lenco, Denon DP80, and Technics SP10 Mk2.) But I would never claim slate is categorically "the best". Moreover, there are several different kinds and densities of slate, even within the US. For example, Vermont slate seems denser than Pennsylvania slate. I have no idea what that might mean. My SP10 plinth is made from Vermont slate.

Dear Raul, I think it is a bit too strong to use the word "charlatan" in this regard. In English a charlatan is a "deliberate liar". If anything, most of us are only guilty of generalizing too broadly from relatively limited direct experience or controlled experimentation, where even in the best of circumstances, the results are based on subjective judgement. So, I can only say that seating the Lenco, Denon DP80, and SP10 Mk2 in slate plinths where I have also coupled the tonearm to the solid slate (no discrete armboard) results in making these three different tables sound much more alike than they did before. And they are all much more neutral; they have lost colorations that most of us can associate with the three products. They are more neutral without being "dead" sounding; the liveliness associated with idler- and direct-drive is still very much in evidence. Ergo, IMO, in this little experiment, slate is good.

Dear Ken, I take it you must reside in the Richmond, VA, area, if you live near Howard. He currently has my Kenwood L07D motor and power supply for parts upgrades and calibration. I look forward to having it back here in Bethesda, MD, for my first listen. We aren't too far apart.

You put one chassis into plinths made of 4 different materials. I put 3 entirely different chassis' into plinths all made from the same material. The two experiments are not comparable. In response to your speculation about coloration, each of those three turntables has a characteristic coloration when auditioned in their respective stock plinths. In slate, they all became much more neutral sounding (which made them sound more alike but not exactly alike) AND the best qualities of those two drive systems (idler and direct) were not merely preserved but enhanced. That's all I can say.

So which plinth did you prefer? You did not say.

One could just as well posit that the differences in sound among the 3 tables are primarily due to unwanted resonances, either within the turntable mechanism or from the respective plinths, and that slate either dampens the chassis resonance or eliminates the resonance of the factory plinth by replacing it entirely. Once that happens, if you play the same LP on the 3 turntables, you would expect/want them to sound more (but still not exactly) alike. That's what I hear. What favors that hypothesis is that the sound is more neutral. The 3 turntables did not take on a "similar characteristic" so much as they became more neutral to my ears. I suppose you could say "neutral is a coloration". There is no resolution through discussion. That's the beauty of it and the frustration too. I am not saying that slate is the only way to go or even the best way to go. But for me, it's all good.

Ken, That would be great, either way. I live just across the American Legion bridge on the Maryland side of the Potomac but right along the river. I am very anxious to get my L07D up and running. Now how is this relevant to the thread? Have any of you guys ever examined an L07D plinth? I don't know what it's made of, it looks and feels like cement and it is as dead as cement but seems more dense than cement. I think it's a proprietary material that Kenwood invented for their top of the line turntable, ever. But they were thinking about the significance of the plinth material in a dd turntable more than 30 years ago.

Dear Intact (Dave?)
I agree with your statement about logical structure. That's why I embarked on the project of acquiring the idler-drive and direct-drive turntables and then making slate plinths for them, so I could hear for myself in my own system. (I also bought a Garrard 301, but I realized along the way that I had no energy left to wade through the Garrard options, plus I grew to love the Lenco, so I re-sold the 301 with no plinth.) Little did I know it would take the better part of two years (of my "spare time") to identify and solve the problems associated with making the plinths that I did make. That's also why I don't feel qualified to make any broad generalizations, beyond slate is "good". Something else might be even better.

I neglected to mention that the Kenwood engineers apparently also valued the idea of Constrained Layer Damping and the use of disparate materials perhaps to spread out the resonances. The L07D plinth is primarily made of the very dense cement-like material described above (if you look at a photo of the L07D, the stuff I am talking about is painted dark bronze or brown and is the major visible structural element), but hidden below and around the motor/platter area we have a sheet of thick stainless steel or aluminum. Below that is a very large piece of intricately cut hardwood (mahogany maybe) which is bolted up to the bottom of the chassis by at least a dozen metric screws that anchor into the stainless steel pan. (The wood piece can be seen peaking out around the side edges of the plinth; it is painted light gray.) Finally, that stainless steel or aluminum piece that surrounds the motor gives off a solid metal "arm" that goes all the way to the tonearm mounting platform, forming a firm coupling between the bearing and tonearm bass, which also contains a very heavy brass anchor-weight. Those guys were not fooling around. When I first acquired the table I had the notion of replacing that hardwood piece with a piece of slate, but it would take both a waterjet AND a CNC machine to re-create the shape in slate, I will leave well enough alone.

Maybe the answer to the OP's question is that it takes a real knowledge of materials science and that possibly a variety of materials used together in a certain kind of "sandwich" would make the best plinth, cost no object.

Theaudiotweak, Not sure whether I would agree with you, but check out the new TT Weights turntables if you like brass.