Wooden platter choice

[Nardis]

I'm planning to build a

[markp]

You are asking for lots of resonances and other wood related trouble. Maybe ironwood or solid ebony would work.

[Nardis]

Wooden platter choice

Whoops! That one went off before I was ready. I meant to say that I am planning to try to build a turntable with a wooden platter.
I have found two 30 cm/12 " wooden chopping boards both made with laminated strips and non resonant. One is made of rubberwood, the other from bamboo.
The rubberwood is made of strips of end grain with the grain running in different directions. The bamboo is in layers with each layer at right angles to the next. Both are very smoothly finished and perfectly circular (as far as I can determine anyway).
Does anyone have any experience of these two woods or views, please?

[lohk]

Faszinating idea!

Please try both. I suppose the bamboo one is lighter, so it is probably more sensitive for the drive but better soundwise (no energy storage etc.)
Difficult will be the drilling for the central axle/bearing though.

[uli]

wooden platter...

http://www.diyaudio.com/forums/showt...841#post533841

Uli

[analog_sa]

wooden platter...

This ain't no wooden platter; it a VPI.

AFAIK Teres are the only ones braving the woodworms.

The platter material may be important but there is a lot more to making a good TT. How do you intend balancing it?

[Nardis]

How do I intend balancing the wooden platter?

I plan to follow Teres by using a lot of lead shot in both platter and plinth.. I’ve floated one of the platters in a bowl of water with a small circular plastic spirit level in its centre. It was dead level so I assume it is reasonably well balanced- although not to really high end tolerances. I planned to spin it on a lathe at high speed and watch for signs of wobble. I’ve been told it may be possible to take it to an engineering lab here in London to get it professionally checked, but that will cost money.

I want to commit as little money as possible until I hear that it sounds a promising direction. If it is obviously worth pursuing I will then think about spending on it.

My recipe so far:
Base:-60mm thick wooden chopping board, to be drilled and filed with lead shot and maybe tar.
Platter: either the rubberwood (70mm thick) or the bamboo (60mm) platter I described, drilled with 12 pockets for lead shot like the Teres.
Bearing: borrowed from a Rega The Rega bearing is apparently used in some commercial turntables with very high mass platters. I’ll sit the wooden platter on the Rega bearing assembly’s plastic subplatter.
Motor: either the Rega motor, with added external power supply, attached to the wall and with a silk thread driving the subplatter.
Or: the battery driven DC motor currently driving my Michell with either silk thread or videotape belt driving the platter rim.
Arm base: hardwood discs (I have some Iroko) laminated, maybe with 2mm lead, drilled to accept the arm assembly and Rega arm from my Michell with minimum fuss. The Michell arm board attaches to the subchassis with 3 bolts with spacers to give the correct height. I may have to swap the spacers for slightly longer or shorter ones.
Isolation: 4 BMX tyre inner tubes (smallest available) supporting a slab of slate.
I reckon I can get this up and running at modest cost. If it works I’ll invest in another bearing and motor and put the Rega back together. If it doesn’t work I’ll have spent very little and can still put the Rega back together.

[analog_sa]

The Michell arm board attaches to the subchassis with 3 bolts with spacers to give the correct height. I may have to swap the spacers for slightly longer or shorter ones.

Your general idea seems ok. Of course there is no telling if it's going to actually sound any good and even if it will sound better than the rega on all fronts. My modest experiments show that the arm support is pretty much a deciding factor soundise. A slate/alu sandwitch in the armboard made a significant improvement.

Make sure you listen before and after the lead shot. It certainly brings overall improvement but also has a specific signature you might not like.

[primalsea]

This is something I herd from a guy who worked for IRD. They made VERY acrurate balancing machines for things like turbines that spin tens of thousands of RPM so I guess it must be true.

He said that the more mass something had the less acurate the balancing had to be. This is partly because heavier things tend not to be spun as fast as lighter things. The idea here is to think of hard drive rotors, light and fast, and large electric motor rotor, bigger and not so fast.

However, also the heavier mass object has more inertia (is that spelt right?). Once its spinning the force due to the imbalance has to overcome the mass & inertia of the spinning object itself. So if its heavy and spinning slowly even a relatively unbalanced platter will cause little problems.

It was a while ago and I'm not an engineer but I think the above is correct but please check it out before you totally beleive it

[Geek]

Question for those in the know:

Would not a harder softwood (fir/spruce) be better at killing resonances? I have worked with hardwood exotics, like Purple Heart, Bubinga, Wenge and in a symmetrical form, they resonate ring like a glockenspiel