SP10 Mk II vs Mk III

Hello everybody!

I am new of this forum. I am writing from Tuscany, Italy, where i live. I happened here looking for info on how to build a plinth for the SP10 MKII. I went quickly to the posts and there's already so much information that I must first of all say thank you to everybody.

My SP10 is flying here from Australia just now, i got it on ebay (from a respectable seller) a few days ago. I hope it will arrive safely...

I think that building a plinth is great fun! Also nice that all SP10 will look very differntly!

I've seen Albert Porter's plinth on soundfoutain and ordered there the template. So now I am working on the plinth project. I really liked Albert's ones (except a few minor hestetical choices), and I will probably work on the same ideas. Specifically i would like to ask you all if some of you has experience with graphite (carbon block) as a mean to add mass and dampen resonances. I can acces a cheap source for this material as well as a CNC machine to work it, so i wondered if it could be of any use.

Meanwhile, thank you again.

Dear Dgarretson and Lewm,

Thank you for your promt reply! But i think i shall avoid a probable misunderstanding. I am talking about graphite block, not carbon fiber. The density of the material is about 2.2 g/cm3 ie. 0.08 lbs/inch3. So not very heavy, nor light tough. It is made of heavily pressed carbon powder, its structure is amorphous. It is available in different densities and hardnesses.

As soon as possible I'll try to post a sketch, so it will be easier to understand each other.

Again many thanks

Thank you Atmasphere, one of the things i am mostly uncertain was if the arm base should be coupled to the motor or somehow decoupled (ie. arm base on its own, more or less, as you see in many differnt designs). I appreciate your point of view.

Hello Lewm,

I've been a silent reader for a while... Thanks for the question. And yes, that's the material. It is available in different hardnesses-densities (the densest the harder).
My idea is to use it along with plywood using a very thick slab (about 2') in the middle of the "sandwich", in this way it will be protected, add mass with a diffrent resonace curve, and a quite dead material halfway. That slab will be also used as the base for the armboards (to be done from thick blocks of the same material, that i know is good for the purpose since i am already using it).

To further add mass I tought to make a bottom steel plate "a la" Porter, only I tought to make it bigger so that all the screws of the motor unit will go there. The "screws" will be made out of 1' brass (or steel?) tubes worked at both ends.

Now a few questions, one for Mr. Albert Porter (by chance we are colleagues... funny). Is it there any special warning/advice he can give about the center "screw"? You remove a cup and go in with the screw... but what's there (i am still waiting my unit..)?
The second question is more general. I plan to make those 6 big screws that will pass trough all the plinth and reach the bottom steel plate. Should those screws and the bottom plate have a rigid coupling to the whole structure, or should them (and the plate as well) be decoupled somehow (using a layer of neoprene around the tubes and over the plate)?

...ummm maybe this reading is too difficult (english is not my language, also), is it there a way to post some sketches here?

Well, as usual many thanks to everybody here... all informations and ideas are precious!

Hello Lewm and Albert and Many thanks.

Albert, I probably misunderstood when reading of your plinth on sound fountain, it seemed to me you put the rod in place of the bearing cup, working its end to suit, and felt a bit afraid of going in such mod. Having a rod touching it (with some pressure?) is easyier and safe. Thanks.

In fact Lewm answer was necessary and obvious (it appeared to my mind a couple of hours after posting...) I was so lost in finding a good way to organize the layers that I missed the point!

The graphite market is increasing for various different uses, metallury, batteries, chips (!) so there are many businesses around, big and small where the material is available. It is enough to have a look out of the audio market. Graphite is not exactlly cheap, but it seems that those company making audio products out of it are decuplicating the price of the material (at least...). I get mine from a friend in Rome, he's running a small business of fairly priced graphite audio pruducts and can cnc machine any sort of piece.
But I guess this info is not of much use: if you start shipping heavy manufacts overseas you'll probably loose the good price, I would have a look around searching for small companies selling graphite there in the US, they will very luckily have a cnc machine at hand and hopefully be willing to make a few pieces on design.
But... well, in case your planning a trip to Rome, bringing back some pieces (small) can be done!

Hi Lewm!

True! It really seems i invented it! Funny... I am laughing of myself. Usually "englishing" latin words, specially with unusual terms, works well... well usually, not always!
If others don't get it "decuplicare" in italian means multiplying ten times. Does an english word meaning this exist?