Lenco plinth? How big is too big?

I have an L78, upgraded Origin Live One arm, Empire MC-5 moving coil cartidge, and access to a sawmill with lots of prime cherry wood. I was thinking of a cherry plinth, 17 inches wide, 24 inches long, and six inches tall of cross layered one inch cherry. Then cut off the rear corner where the tone arm is mounted, in a sweeping arc of about 10 inch radius, and mount the tone arm on that detached corner. Use 1 inch thick isomolded graphite disks of 2 inch diameter topped by one 3/8" tungsten carbide ball, and resting on three such balls. Use three of these ball/disk combinations for each of the main plinth and the corner with the tone arm. What do y'all think? I would appreciate any suggestions before actually putting it all together. Thanks. Ralph
Sounds great to me: too big means only more than you can actually carry, so bear this in mind, as you don't want to have to resort to a hoist every time you want to dust! I just finished a plinth which measures 22" x 23" x 6", so your plinth is actually quite small ;-)! To enact the principle of contrained-layer damping (CLD) in order to ensure there is no single dominant resonant signature, you might want to consider jamming a layer or two of some other material in there, but some materials, like maple for instance, sound great on their own. I have no experience of cherrywwod. Have fun, it sounds beautiful!
I made one slighly less than the size of Jean's and it tipped the scales at 65 lbs (plinth alone). Yer fine.
Good. Thanks. I'm looking forward to a big ole plinth. Now that I know it's ok, maybe I'll just make mine even bigger. :) I got the idea of cherry from a Garrard 301 article that mentions Shindo plinths: http://www.6moons.com/audioreviews/garrard/301.html
I've read that maple is the most musical wood, but just have a feeling that cherry would have a darker richer sound, that might nicely complement my RD75 ribbions and Berning EA2-150 amp, which are very slightly on the lean side. I'll post pictures when it gets done. The sawmill guy is just now putting the wood in the kiln, so it will be a while. Thanks again, and I'm thinking on the CDL thing...
be careful about the glue up of the wood. Thick alternating layers of wood can set up internal stresses that may result in warpage. That is why plywood layers are thin.
How big is your room?
Ralph: I noticed in that 6 Moons article from 2004 that it mentioned that Jonathan Halpern wanted to market a Shindo Plinth for < $1000, does anyone know if that was ever realized?
Hi Ralph,

My turntable is 23.5 X 17 X 8. It's about as large as I can handle! Anyway, I submit that the size isn't quite as important as all the other components. How they work in unison is key to the final outcome. I believe you are best served by asking why every step of the process. In my opinion, the justification of every move during the project will yield a better result than any other consideration. In other words, don't just fly into it. Making a rational analysis for everything has a potential for a big payoff at the end. Try to consider every part of the turntable, and every part of the plinth, in a big way. If you do that, you can't lose.

In short, research everything, no matter how small.

Best of luck!
Ralph, I am not sure I can properly visualize your method of mounting the tonearm, that involves cutting off a corner of your plinth. It sounds as though you intend to de-couple the tonearm mount from the major part of the plinth. There are differing opinions on this, but lots of smart guys think that the tonearm mount should be tightly coupled to the plinth and hence to the main bearing of the table. This sounds like a good idea to me. If my perception of your design is correct, you might want to re-think the mounting of the tonearm. Maybe Win and Jean can chime in on this topic.
Lewm, I had the same impression from Ralph's arm mount description and the same sense of caution.

In ongoing design for my SP-10 plinth, I'm intending to bolt down the armboards (2) with brass machine screws. Each armboard will be 3/4" thick and replace that section of the top 3/4" layer of birch ply. The idea of cutting off the end of the plinth then reattaching the arm somehow sounds questionable to me.

Ralph, concerning how big, you might want to read some of Jonnantais' experiments with various plinth materials and size.

I am probably in the minority here when it comes to the issues surrounding tonearm coupling. I do believe that mounting the tonearm to the plinth in a secure way is indeed the only way to go, but I stop short of your comment regarding an interaction with the bearing. Still, it should be a non-compliant mount, in my opinion. All this begs many questions about isolation, neutrality and what it all means. It also goes to the issue of dissimilar materials in the build. Should that apply only to the plinth? I don't believe so. What I do believe is that every small part, and how that part is applied, counts. I also believe there are various ways to get there, and in the end very different turntables can reach the goal. It is a very complex process, and there are no fast answers...unfortunately.
Win, I probably overstated the case for tonearm coupling. As you know, there ARE those who do advocate firm coupling to the bearing. However, your opinion carries a lot of weight with me (at least 200 lbs of slate). Anyway, I think we both agree that mounting the tonearm completely outboard of the plinth is not optimal. Like Pryso, I am also building an SP-10 plinth, so these considerations are very much on my mind, too. Ralph, I hope you get the picture.
So if I understand the utility of a good TT plinth is to damp vibrations as much as possible. Layers of different materials and added weight/size matters to achieve good damping. Nature of materials too.
I think Ralph has left the building. :)

The purpose of the plinth is to support the deck in a user friendly, high waf structure, and prevent unwanted vibrations (from inside or out) reaching the stylus. Use minimum 6 layers of 18mm ply or 30mm of slate. :)

High waf structure ? You mean a nice design ?
I must have a particularly nice wife. Either that or she has a diminished esthetic sense. I've got three turntables sitting on the floor of our living room aka listening room, not to mention the one I use which is on the equipment shelf. And at the far end are the enormous Sound Lab ESLs flanked by huge and rather ugly OTL monoblocks. She never says a word, but she may be planning to kill me. No, in fact she's just a good egg.
Hi Lewm,
Three turntables sitting on the floor? - no doubt paying close attention to the one you use, like students in class? :) Like to see a pic of that Lew. ;)

Five decks set up and running in the den here, a cartridge shoot-out that's lasted a year or so. :)

Hi Jl,

"High waf structure ? You mean a nice design ?" not always the same thing, but yes something like that.

Last spring I went a bit off the deep end, for me, as one who always wondered why on earth anyone would want more than one turntable at a time. I already had the Lenco and a Garrard 301 in a box in the basement. Then I saw a Denon DP80 in mint condition on eBay, at a price I could not refuse. Then I thought I'd better get an SP10 MkII, before they are all gone... And the beat goes on. I also bought an extra Lenco, because it was so nice and so cheap. Now I'm thinking I will have to sell at least one in order to afford to get the others up and running, but I cannot decide which one.
I hear you. :)

As I roam the thrifts, boot sales, and second hand shops, I am regularly asked 'how many turntables do you want?'

'All of them' is my reply.

As for how many do I need? - just the Lenco L70, with the AT1005 and the Decca. :)

The rest I'm just saving from the land fill, for a more enlightened space in time ............ :)