Damping Platter With Liquid Latex

by **JBonner** » 05 Jun 2011 16:06

My Logic DM101 platter, while substantial, rings like a Tibetan singing bowl, even though it has felt bonding on the upper surface. The addition of an extra felt mat does little to help. I'm quite interested in getting an old AudioRef Le Mat or some such but have been considering other damping options.
This cannot be an original idea, so if anyone has tried filling the inner platter surface with liquid latex I would be really interested in their results.
I thought of using about 250gms of latex rubber liquid, masking the central opening with a ring of cardboard, and letting the mixture find its own level. Obviously, the platter would have to be totally level itself.
Any thoughts on this anyone?

(previously posted by mistake in Technics Forum - apologies for any duplication)

by **Eoin** » 05 Jun 2011 16:22

Sounds like a bloody good idea to me. There's a VE member that did some testing on damping and a particular type of pro modelling clay came up as a good option. He hasn't tried latex but I bet he could be persuaded to run it on his rig if you sent him a sample..

by **Eoin** » 05 Jun 2011 16:28

Cats Squirrel is the chap you want (I just searched); he could comment on whether it'll provide any damping. Sounds like a good idea to me could even be loaded with 'stuff' that might help (whatever that might be).

by **JBonner** » 05 Jun 2011 16:48

Many thanks for your prompt reply (us Sussex folk need to stick together...)
Always nice to have a bloody good idea, nice but sadly, in my case, rare. I really do think this one might work though, which is why I assumed there must be a million people out there who have already tried it.
One can buy the latex in any good model shop for mold making or a theatrical suppliers for masks and wounds etc. I found lots on eBay.
It comes in all manner of compositions with additives and thickeners. Not too pricey either, for the quantities I had in mind.
To me, the main advantage would be the self-levelling quaility - got to be easier to retain platter balance compared to other forms of dampening like Dynomat and so forth.

by **Eoin** » 05 Jun 2011 16:51

Sussex, eh? Whereabouts...

The main issue will be balancing. If the platter is off level then you'll end up heavy on one side and that'll be no good at all.

I'd try it myself but I've got a donut shaped platter that goes on a four or five inch inner platter and I can see that'll be tricky to mask up and prep if it's to be even and balanced.

by **JBonner** » 05 Jun 2011 17:16

I'm near Hastings, and very nice it is too at the moment.
I agree that perfect levelling of the inverted platter is essential.
The Logic's platter is also a two part doughnut but I thought to mask off the inner cut-out with a ring of stiff card and then trim back if required when cured.
Well, that's the theory...

by **mattlynch** » 05 Jun 2011 17:19

hi guys,
i had a thought on this , i know i know but it does happen , :lol:

when i was messing with a project debut II i tried similar using rubber solution, to get an even spread i fitted the platter upside down and ran it at 45rpm and poured it into the edge of the platter ,the rotation spread the stuff evenly and it had a very positive effect, i cant say if i got a truly even weight balance as the debut is not suspended but i certainly didnt get any adverse effects , keeping in mind that latex or rubber solution is easily removed if you dont like it ,it has to be worth a go.
please let us know if you try it and what sort of effects it has .
all the best,
matt

by **Eoin** » 05 Jun 2011 17:30

JBonner wrote:I'm near Hastings, and very nice it is too at the moment.
I agree that perfect levelling of the inverted platter is essential.
The Logic's platter is also a two part doughnut but I thought to mask off the inner cut-out with a ring of stiff card and then trim back if required when cured.
Well, that's the theory...

That would work.. But tricky to get it circular and centred.

I am thinking I could do it upside down with the subplatter in place. Could put insulating tape or whatever round the subplatter to 'thicken' it and provide some clearance. Lube the tape with some light oil or grease. Pour the latex mix, then when hardened the subplatter will slide right out (we hope). Tape get removed then there will be some clearance in-between the sub platter and the new latex compound. The hole in the latex should be central and circular.

Also a bit of Vaseline or grease where the main platter rests on the sub might stop the latex mix leaking out before hardening.

How does that sound?

by **JBonner** » 05 Jun 2011 17:43

It sounds like we are moving towards a viable process here.
The idea of spinning the platter to aid even distribution is well worth considering. That might only work with a fairly loose mixture though.
I do feel an experiment coming on.

by **PatP** » 05 Jun 2011 17:45

It sound like a good idea so give it a go! I bet it will take a long time to harden though so it may be worth just doing a thin layer at a time.

I used some Fimo polymer clay on the underside of my Revox platter. The cast metal construction left convenient equal sized and spaced recesses around the outer edge which I stuffed with weighed-out bits of the clay. This resulted in far less ringing.

by **Eoin** » 05 Jun 2011 17:49

PatP wrote:It sound like a good idea so give it a go! I bet it will take a long time to harden though so it may be worth just doing a thin layer at a time.

I used some Fimo polymer clay on the underside of my Revox platter. The cast metal construction left convenient equal sized and spaced recesses around the outer edge which I stuffed with weighed-out bits of the clay. This resulted in far less ringing.

I think it'll 'go off' more or less evenly even if thick. If I try my method then I couldn't spin the platter, it'd be one or the other but I guess it'll level up anyway.. Depends on how sloppy the mixture is mixed too.

What do you think, Matt?

by **bastlnut** » 05 Jun 2011 18:36

hallo,

the problem is going to be that you will have to dynamically balance the platter after the latex has cured.
otherwise the suspension will wobble at speed.
as the softeners dry out with aging, you will have to rebalance the platter again from time to time.
best bond a layer of cork or neoprene with the liquid latex and balance the platter by trimming the binded material.
this will also slow the aging process because of less air getting to the latex.

of course the other problem is that you will be adding weight to the platter thereby making the suspended parts more top heavy,
which is what you do not want.
the weight should be in the sub-chassis for better stability of the moving parts.

regards,
bas

by **jimg** » 05 Jun 2011 18:40

Good idea, but a couple of points. I have two DM101,s and while .like most two part platters they ring when parted , are less so when together. Also the motor pulley is quite tall on this deck and has limited clearance under the platter so you would have to take care it does not foul the damping layer. But it is easy to raise the subchassis level a few mm to compensate.

by **JBonner** » 05 Jun 2011 22:07

I am not too worried about adding extra weight, I have already up-rated the springs to take account of the extra damping I added to the sub-chassis and there is adjustment available..

The clearance between the pully-top and the platter under-side is an issue, on this deck at least.
There are ways 'round it, as you suggest, but needs pondering on.

Reassuring to know that the platter rings less when mounted on the inner section. It's obvious now you mention it. The assembly is very well engineered and mated. In fact the turntable as a whole is superbly made. I've made some modifications but the design and manufacturing is excellent.

May I ask what mats, if any, you have tried on the 101s?