Designing a Plinth

Jimbo3, Cocobolo is a very dense wood. It has a density along with other woods like maple, rosewood, cherry, etc. These various densities are also very similar to MDF (medium density fiberboard). In most cases MDF is chosen for not only it's density, but also for it's ease of fabrication, not to even mention it's cost, especially relative to a solid "block" of Cocobolo. God forbid you accidentally "slip" when fabricating the Cocobolo.

You have probably also noticed many manufacturers choose to use an acrylic material for their platter. There is a method behind their madness. Acrylic, aka: Metacrylate, has a mechanical impedance characteristic that is very similar to vinyl. Your plinth will have a mechanical impedance also.

There are going to be areas in which you will need to "decouple" from vibration and other areas where you will need to "drain" vibrations. Especially with a non-suspended plinth.

Click on the websites below for a "primer" in DIY turnatables.

http://www.decdun.fsnet.co.uk/turntables.html#ttplinth

http://www.diyaudio.com/forums/showthread/t-18614.html

Well, the cost of cocobolo is not THAT bad. I wouldn't use a solid block either. Much easier to glue up pieces so you do not have to worry about wodd "movement" down the road. You can get enough to build a plinth for about a hunded bucks. Believe me, I know. Using acrylic is actually more expensive. the two I have going now will use about $200 worth of Staron each. Plus, the glue, glue gun, and tips are EXPENSIVE!

I actually think the wood is easier to work with.

Jimbo, don't know if you saw it or not, but here's the link to my TT project:

Joe's Teres

It's not that hard to do if you know what you are doing. By far the hardest part is making sure the boring for the bearing is correct. Every thing else is only limited by you imagination.

If you want any advice, email me. I'll be more than happy to share what I've learned.

Joe

I have been considering a variety of option for plinth making, myself. I would like to go the whole nine yards and do something very elaborate in terms of wood grain matching, inlays, etc., etc.

I am thinking of beginning, though, by making a plinth to replace or interchange with my stock Nottingham plinth. Fortunately for me, I have had a good deal of experience working with a large number of wood types. In addition to cocobolo (expensive because it is a hot item tight now), I am considering some woods that are beautiful, of different "colors", dense, and STABLE. A few on my short list include:

Mara (NOT Mora) - An absolutely GORGEOUS honey-colored wood, sometimes with striking dark streaks. Very dense and very stable.

Cebil - A wood that is very similar in looks to Black Cherry but is much denser, harder, and is very STABLE.

Quina - A reddish wood that can take the flavor of a very rich Honduran mahogany (with a more regular and wider graining) and can have very nice figuring. It is hard, dense, and STABLE. It is widely used in South America for cutting boards.

Argentine Lignum Vitae - Yes, a cousin to the more tropical cocobolo. However, this wood is generally much lighter - a sort of olive/green, not unlike some of the darker (not redder) oaks. Takes a mirror-like polish, too. It is a bit resinous, though, so an appropriate sealer is a must.

OK, I know that these woods would provide a very dense and stable plinth. Whether or not they are "musical" woods would be fun to determine. These woods are not overly expensive and someone might have a blast experimenting with them.

Keep in mind that a solid piece is not the way to go to insure stability and resonance "transfer" (if I am using that word correctly).

Jphii, I just had to tell you, absolutely beautiful work. How does it sound? I also, am capable of creating a turntable of this quality.

My tool of choice? A checkbook.

My compliments Joe.

I've been interested in doing this with a well tempered myself, But how is the bearing mounted to the well tempered plinth?

4yanx- How does Mesquite compare in hardness/stability to the woods you mentioned? A local guy told me that it's twice as dense as Red Oak. Could probably get a couple of pieces for next to nothing, but wouldn't waste my tome if it's not an excellent choice.

Also, from a previous post, I suppose I could drill in a few large holes in the plinth in the portion under the platter and fill with shot/sand/oil mix. I suppose that the proximity to the bearing would be good in draining it's energy??

Jim

Jimbo3, mesquite is very hard and dense but I don't feel it passes the "stable" test. Mesquite is also brittle and, more concerning, often has inclusions or cracks within the wood that are not apparent. It is a gnarly tree so it stands to reason. But the grain is fairly straight, and since I would be piecing together a number of smaller piece were I to make a plinth, I might consider it worth a TRY if I had enough to be very selective. Bottom line, it would not make MY short list but, if cheap, all you'd be out is your time.

Thanks, 4yanx. I'll probably go with one of your recommedations. You indicated that there would be a number of pieces to the plinth, but I was thinking that it would only be about two or three pieces glued&screwed together to come up with the right thickness- am I missing something?

Cadet1, I think the bearing and the arm tube are simply a press fit into the plinth. See a picture of the bearing under "accessories" at .

Jim

Cadet- I guess Agon's system didn't like the website I refered to in the previous post. Try this- Stanalog dot com.

Jim, I have some of my own ideas with respect to grain aligning and using what I call "switch-back diagonal piecing" within the platter which I'd like to use. However, I have not fully worked out my approach, as yet.

Joe has already done one, I assume using the Teres design directions, and perhaps he can share that piecing and gluing method for an immediate project. Likely, the lead-shot weighting pattern, too.

Of the woods I mentioned, all except the Argentine LV are roughly half the cost of cocobolo.

I just checked the price of the Lignum Vitae. It's $5.80/lb and a cubic foot weighs 78lbs. So, thats $452.40 a cubic foot! Maple is about $60.00 a cubic foot for comparision. They have a little over at the local lumber supplier and I have touch it every time I stop by. Can't afford it but at least I get to hold it in my hand.

Good luck,

Prpixel, there are may varieties of Lignum Vitae, but wow!. Where do you go that charges for wood by the pound?

I find it interesting the fact that it is more costly to use acrylic than certain exotic woods...if there is a method to the madness of using acrylic, perhaps there is a madness to the method of using wood.

I certainly like the look of wood.

Jimbo,

I'm curious about the design of the plinth. Are you trying to model it after the WT table or come up with a different design? Also, do you have a jointer, planer to work down raw wood and also be able to glue joint smaller widths? If so, your possibilities could be real interesting. I was thinking of an Ebony Top, Rosewood middle and a Ebony bottom. I would also consider using the WT feet.

Quite a few years ago, the square motor days, a guy in the Chicago area was custom painting the tables & some looked very sharp.

Steve

4yanx,

I buy wood regularly from about 6 different suppliers on line and two local suppliers and they all sell tropical lignum vitae by the pound because it is so rare. One local supplier charges $95.00 a foot for 1" dowels! However, I did find one supplier that was selling Argentine lignum vitae for $15.00/ft.

Mara is not very stable, although it is very beautiful. Looks similair to chestnut.

DESCRIPTION: Heartwood is light brown in color, soft, easily worked, but not durable. Member of the rubbertree family. Typically used for crating or as a secondary wood in cabinet making.

Cebil looks like a winner, but I've never worked with it.

Quina has a spicy scent that is used in perfume making. It tends to burn and tear out like purple heart. I made a jewelry box one time from Quina and I swore I would never work with it again.

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I have a passion for rare and exotic woods. I have a little 6'x6'x7' wood shed that has about $10,000 worth of exotic and rare woods in it. Although, it's probaly less then 300 boardfoot of wood. Some of the species include amboyna burl(extinct), fiddleback japanese peanut wood, pomelle cherry, pomelle white oak, curly avodire, quilted bigleaf maple, beeswing satinwood, quilted and pomelle bubinga, fiddleback koa, madrone burl, turleback koa, quilted sapele pomelle, quilted douka, quilted makore and sequoia burl. BTW, I keep the "common" wood in a different shed.

It's an obsession for me. Sometimes I spend days tracking down a rare species of wood. It takes a lot of time to decide what to make. Somtimes I only have enough material to make a small jewelry box, or a clock, or maybe a book rest. Somtimes I have enough to make a stunning occasional table. I usually end up giving away about half of these items to family members as gifts. And, I never throw away the scraps. You never know when you'll need them to make a knob or for inlay.

Hey, some people collect art. Some people collect audio gear. I collect wood.

Now, if you will excuse me, I just found some gorgeous Quartersawn Curly Shedua that I need to purchase before I go back to bed.

BTW, hickory is one of the the strongest woods on the planet. Incredible high shock resistance and stiffness. Hear's an idea, make the plinth from hickory (no sap wood) and cover it with 1/4" or 3/16" exotic veneers.

Good luck,

Guess I have been lucky in that all five of my sources for wood still sell by the board foot (veneers excepted), even exotics. Of course, I have known three of them for over 40 years and my grandfather knew their father's before that. Most I find in 4/4 but sometimes 6/4. It has been a long while since I priced tropical LV, but the Argentinian is much less than what you all are paying for the tropical. I am paying $9.00 a foot.

I am not sure where you got the description for Mara but it is used in furniture in South America extensively. It is beautiful and I'd still be willing to give it a try for a plinth. This is a description I looked up. I was basing my description earlier on my recollections of working with the wood:

"Mara - golden-brown wood with dark streaks. Grain is highly variable. Works well and is very stable. Rare, but used for fine furniture building when a highly-figured wood is desired."

I, too, have used Quina but did not have the unfortunate experience with it that you did with the jewlery box. I understand what you are saying with respect to tearing out, though I would not go so far as to call it tearing out or think it in the same category in this sense as purpleheart. This is a description I found for Quina:

"Quina: A pinkish-red wood with an oily feel and incredible perfumed scent that lasts. Beautiful figure. Extremely durable, this wood is widely used for items like window and door frames, counter tops, cutting boards and flooring. Fine textured, provides excellent polish. Heartwood color is deep red, sometimes with purple highlights and high natural luster. Good in-use stability, but can be difficult to machine due to interlocked grain.”

I would very much like to drop by and view your collection. I don't have the room to keep a stock anymore and I'd love to have some of the fiddleback Koa for a guitar I will build someday. Any pieces big enough for a back, Even a two-piece? I'd like to see the douka, too. Madrone Burl. I knew a guy once in Oregon who had a wood stove and when I went there it was putting out some HEAT. Turns out he was burning Madrone.......

Get ahold of some Cebil and give it a try. It is actually the one I was leaning towards for my project.

I like your mention of inlays as I am the fifth generation of a long line of marquetry nuts! :-)

I take wood descriptions online with a grain of salt. I once bought some "exotic" african wood; turned out to be the local equavilent of cheap pine. Ended up using it for templates and cauls. I came across a description for eastern douglas fir on a foreign site one time. It went on to describe how popular it was in the US for making fine furniture. And, they were selling it for about $8.00/ft!!!! About the only furniture they make from fir is frames for chairs and sofas to be upholstered.

What I ment by tear out is the way that purple heart wants to splinter when you try to route it.

The Argentine LV looks better then the tropical stuff (in the pics), and you can't beat the price. Seems to polish up real nice.

Hey, another wood to consider for a plinth is jatoba, hard and dense and very beautiful.

Smotyka- No, I'm not looking to replicate the WT plinth. THe thought was to do simple straight non-parallel cuts on about a 2" thick piece of wood. Either triangular or a 4-sided piece with the right side being only about 4" deep- just enough to handle the arm and armrest.

I don't have any woodworking equipment to speak of, so the project needs to be simple. If need be, I can find a little time on a planer.

Alot of species have been mentioned on this thread, but I wonder which would have the best characteristics for a plinth considering resonance and other such technical issues. Maybe a sandwich of ebony and rosewood might be a good combination!

Jim

Jimbo, I have been sitting back with great interest reading this thread as it has progressed. There have been some great contributions. I was impressed by the workmanship entailed in Jphii's turntable.

Last evening, I stumbled across the website I have provided below. I have never seen such a complete and diverse offering in terms of wood selections and pricing. Maybe that it is simply due to my lack of knowledge and exposure in this subject. Although, I found the "Musical Grade Hardwoods" section particularly interesting.

Hopefully it will provide some additional info for everyone involved. Ed.

http://westpennhardwoods.com/default.htm

OK guys, I see this has taken off a little since I last checked in.

David, since I've done both wood and acrylic, I assure you it is true: Acrylic costs more. And it does not have the forgiving properties of wood. I like your wood list, some would look very interesting. Also, there is basically no Teres design directions. Just a set of dimensions that I chose not to follow too closely. I went bigger all the way around, and figured out my own shot loading pattern. Description follows....

Prpixel, a man after my own heart. I try and keep every little piece and scrap of exotic wood I can find. Veneer too. How else can you be with what wood costs these days? I agree that the pieces come in handy for inlays, accents, etc.... Luckily I don't have to worry about storage, because my shop has about 4000 square feet. Then my buddy Paul's shop has another 4000, and that's where the serious wood is. I may be the only person I know who has made cauls out of cocbolo. I had a cutoff from my plinth that worked perfect! You may be interested in my wood guy. Check out his site:

East Wake Hardwoods

Rodger has a great selection and is a hell of a guy. Last time I was there I spent 2 hours perusing. He has some estate cocbolo form the 1920's in 8/4 that is to die for. That's what I used in mine. Almost all of his wood (99%) is priced per board foot. I collect wood too.

Jim, when I did my plinth, I used several pices of cocobolo and one piece of ebony. I used 2 pieces of cocobolo for the bottom, about 2" thick glued on the indside edge. For the top there are 4 pieces (3cocobolo, 1 macassar ebony). The two outside pieces are solid cocobolo about 2" thick, glued to the two center pieces. THe ebony is about 3/4" with another piece of cocobolo under it. They were glued up first, the the outside pieces glued to them. Then the top and bottom were glued together. DO NOT USE SCREWS! EVER! The grains run in different directions on these two pieces to give it some added stability. Then came the veneer, which is a whole other story. The shot pattern is kinda, but not really random. I drilled 2" holes 2 1/2" deep, put EXACTLY The same amount of shot in each hole, and plugged then with teak. If you look at the pics, the teak has some really nice grain that is the same on all of the plugs. That little detail took two hours alone.

So, there you have it. Now, on to some materials issues. Jim, ebony & rosewood would both work and look very well. But remember, macassar ebony runs about $50 a board foot. This can make mistakes costly. Teres makes plinths out of rose wood, and I used Madura, a brazilian rosewood for my base. It is similar to cocobolo, but not quite as dense. I would have to say there is no "best" material. There is a lot of good, some great, but too many possibities for a best. Lead helps. I don't think anyone will disagree with that. Use #9. I got mine on the net.

Also, I have found that almost any wood will tear if you are not careful. Macassar ebony is exteremely hard, but tears very easily. I've worked several woods that I swore I'd never touch again. When it happens, I usually just put down the tools, go have a smoke, and give it a few minutes. If I can do this before I throw the piece across the shop, I can usually figure out what I was doing wrong, and fix it. BTW, with acrylic, no such luck. I won't admit to being a master of solid surface material, but I have done a shitload of countertops and sinks. Since my brand, Staron, is 100% acrylic I thought it would lend itself well to TT's. Right now, I need to overcome some issues that do not arise doing countertops. But it looks very promising so far.

On cones, I and others here still think Audiopoints are the way to go. I have them under my plinth and under the base. No matter how you build the plinth, these are very important for a non-suspende table. All you have to do is try the cone of your choice and you will definitely see what I mean!

Buscis2, if your tool of choice is a checkbook, email me!

And I'll say it again: The only affiliations I have are with me.

Prpixel, I only provided the descriptions of woods that I found in a catalog after giving my own description previously and as an alternative the description you gave of Mara which looked for all the world like a cut and paste. Yes, the descriptions of some woods (not unlike audio components) can be deceiving depending on what the marketer is trying to market.

Having worked in or around a wood shop for 40 years, I knew EXACLTY what you meant by "tear out", I just didn't find it the serious problem that you did with regard to Quina. In retrospect, though, it is probably not the wood I'd suggest to someone who has not used it in more than a few projects or to someone who does not have at least some commercial-grade machines, like a shaper and joiner.

I like the look of the Argentine LV better myself. At the $9.00 I was paying (my guy says $8 today), it isn't badly price. At the $15 you said you're paying, I'd maybe think twice.

Jim, an ebony/rosewood combo would be beautiful. Because I am just getting into this with respect to plinths (not sure I want to go with wood for a platter just yet) I apologize for not being able to offer better suggestions visa vis resonance issues. I know what would sound good and the differences between many woods for musical instruments, but a good number of those would not offer the best properties for a plinth. Since Teres is one of the first companies to offer wood platters and plinths on the market (at least to the degree they use wood) perhaps they have done a comparison of numerous woods and would share the results of those that they reject and why. But then, what sounds good to some might not be the choice of others. In the end, I think the field is very open with respect to what wood is the best combination of looks, performance, and workability. Hopefully, more than a few of us will give it a try and report our impressions. In time, I will certainly do so.

8/4 cocobolo, Joe (he said slobbering at the thought)?

Ok, I'll plead ignorance- What do the numbers such as 8/4 and 4/4 refer to?

Ed- Thanks for the West Penn website.

Jim

Joe, let me ask you this. How did you establish the outer circumference of your platter? Were I to make one, I was considering attaching stock to top and bottom and turning it on the lathe. A shaper and jig might work. Of course, a band saw and shaper is the usual choice for non-critical stuff but I am thinking that the circumference should be pretty damn consistent to achieve rotational stability. What have you found in this regard?

Jim, the dimension is based on 1/4" thicknesses. 3/4 = 3/4", 4/4 = 1", 6/4 = 1 1/2".....Joe's mention of 8/4 cocobolo is 2 inches thick.

The West Penn site is interesting. There are MANY sites offering exotic hardwoods these days, some more reputable than others. In the end, most all are very good places to go look at pictures of different woods and to learn of some their characteristics. However, it is always best to find a dealer locally if at all possible. That way you can go take a look and decide for yourself with some expert advice many dealers can provide. Plus, the shipping costs for more than just a small amount of wood can be STEEP. I know of quite a few folks in the business of using exotic woods. Depending on where you are located, I might be able to offer a suggestion or two. IMHO, it is worth a couple hours drive if it means being able to select just the right piece or, perhaps more importantly, have the ability to reject a piece without the hassles and expense of returns.

Jim, 4/4 designates the material thickness. 4/4 would 1" thick, 8/4 would be 2" thick. 5/4 for example would be 1 1/4" thick. BUT, (just to confuse matters) this is not always the actual thickness.

The site offers "dimensional hardwood lumber". A 1"x4" is actually 3/4" x 3 1/2". Although, I don't know if that is the case with lumber of the "non dimensional" type. You would need to consult with the other contributors to this thread, as I have no expertise in this subject.

One reason I ask about using the lathe (or a shaper) is that I would then gouge a groove or five and then use some bandings to highlight the platter edge, examples of which can be seen in the link below. There are a variety of other source for these bands, too. I have modest collection of inlay patterns I've used when building other furniture and my uncle has a set he has made that is downright staggering - though his skill is at a level that mere mortals such as I can only aspire! ;-) The variety of inlay possibilities that might be applied in the crafting of a plinth seems endless and well, exciting, at least to me.

Bandings

This is from the West Penn site:

"DALBERGIA RETUSA

Cocobolo is a member of the Rosewood family. It grows in the drier uplands on the Pacific side of Mexico down to Panama. Extremely oily it will reject almost any finish except wax. It shines up to a nice luster. Even an oil based varnish will not stick. There is no treatment that will make it suitable for bonding with glue, but it can be nailed or screwed easily. It is waterproof which is excellent for making knife handles. It smells like lilacs while it is being sawn or sanded. It varies in color from red to yellow and striped with black to lighter black. It darkens with age."

Sounds like drivel to me since I've done everything to it that they say can't be done. Also, I only paid $14 a foot for 8/4 that has been sitting since the 1920's.

David: On the platter we've been "having a time" as they say. I finally found that the best way do do it is with a router. Band saw down to close, and then use a template I had made out of steel. A friend of mine has access to a machine shop at work so he had a couple different ones made. This will make it a hell of a lot easier to try different arm boards and plinths. I can also get perfect cauls for gluing the veneer. May go the vacuum bag route here, not sure. I like doing things the old way some times. I'm going to do another plinth for myself too. I need to have two set up to evaluate pieces as they are made.

Our biggest lathe will only turn 11" so we have had to come up with alternative methods. I wish we had one that would turn 14" for the options it would give me. But, I can do just about anything either with a router, shaper, or by hand that I cound do on a lathe. Just about.

Teres uses Jatoba cores for it's platters. CB only made one solid cocobolo platter for the 340. The prototype is 4" thick and weighs 40 pounds! I'm shooting for the same size. I'm doing it in two pieces so you wont see any of the holes for the lead. I'm also trying some different lamination methods for stability. Veneer will be a must for cosmetics. Maybe some banding or inlay. But first I want to make sure it will work. I won't know how true it will run till I get it mounted. But, I'm no rookie!

Jphii, I also found that highly unusual. But again, I won't pretend to know anything about this stuff, cause I don't. From the theoretical mechanical/electrical design/engineering aspect, I could hold my own. But when it comes to the actual woods?

I subscribe to the old theory:

"Better to be silent and thought the fool, than to open the mouth and remove all doubt".

Something like that, but I'm sure you understand what I'm attempting to say.

I was actually trying to find a website that provided resonance/excitation frequencies, and vibration dissipation characteristics of wood (I have no life), but with no success. Does anyone know of such a site?