Damping Platter With Liquid Latex

[Rap]

[I'm not answering any more of your idiotic rhetorical attempts to fluff over your mistakes Bryan. Twisting words and rhetorical b.s again!

Could I please ask that you refrain from making personal attacks on other members, as per the forum rules. It is fine to disagree but this type of reply is not conducive to open debate. Thanks for your understanding.

Regards,
JaS

Noted, won't happen again. Though I was referring to the rhetoric and not CS.

[Ldg]

Hmmm. I just looked at CS' website which cites 'damping factors' (eta) for various materials, at least half a dozen of which I have published standard figures for.

The metals are generally in the correct sequence, but a decade or so larger than standard, whether one considers loss factor or flexural loss factor. Cork is pretty well spot on. Woods are about half a decade to a decade larger (but I only have a few figures).

So there does seem to be significant and widespread variance, and not in a simple way. It's not just lead that is at issue.

I thought hard about whether this is off topic or not, and believe it to be on topic because it pertains to CS' on topic posts, and ultimately the correct choice of damping materials and their application.

As I see it, there's plainly a big discrepancy, and IMO that should be borne in mind. It's the sort of thing I would wish to know about before considering using CS' figures when choosing damping materials, and how to apply them.

[cafe latte]

Thanks for your input Lucydog and CS. The reason I mentioned plinth also as the whole TT package plinth and platter must be suject to vibrations so I wondered if one could influence the other.
As much as a nice hardwood will look great I am open to ideas if there are better options. PM me if it is too far off topic.
Re platter vibrations my idler is old and a bit hard, so I for an experiment just glued an O ring (lightly so it is reversable) to the idler which seemed to do the trick. Is this the best way to solve any rumble or is there a better option? I am thinking of using a thick Technics mat on the platter to help damp any noise is this a good idea?
Regards
CL

[steve195527]

very early Linns had the underside of the outer platter coated with a hammerite type finish,not sure if this was for extra damping or just to make the platter seem better finished ,also had felt glued to underneath of outer rim of platter to stop it scratching the SS top plate,the paint was pretty thick so it could have had some damping qualities I suppose,could be an alternative to the latex and it wouldn't trap air or dry out with age

[dlaloum]

Thanks for your input Lucydog and CS. The reason I mentioned plinth also as the whole TT package plinth and platter must be suject to vibrations so I wondered if one could influence the other.
As much as a nice hardwood will look great I am open to ideas if there are better options. PM me if it is too far off topic.
Re platter vibrations my idler is old and a bit hard, so I for an experiment just glued an O ring (lightly so it is reversable) to the idler which seemed to do the trick. Is this the best way to solve any rumble or is there a better option? I am thinking of using a thick Technics mat on the platter to help damp any noise is this a good idea?
Regards
CL

Hi CL

you could look at densified wood...

http://www.valeplastics.com.au/pages/ma ... d-wood.php

There are a few aussie suppliers, and it appears to be the same as what is known as panzerholz.

Bye for now

David

[davidsrsb]

There is a huge difference between the function of the mat and platter damping on the underside.
The mat is the connection from the vinyl to the platter. Ideally it would be stiff, but reality of non-flat LPs and the need to couple the torque of the platter to the LP prevent this.

Damping under the platter is to prevent the platter ringing like a cymbal.
Maybe impedance effects are messed up because the platter is thin in wavelengths, even with the higher speed of sound in metal.
I would expect that the ideal platter should be very stiff compared with the cartridge. You want as much as possible of the tip movement becoming electrical signal.

[Ldg]

Hi Davidsrsb. Yes, most platter vibrations probably follow Bessel function patterns, because metallic platters are often relatively thin. Impedance effects must remain in play, of course, but analysis might well not follow flexural beam behaviour.

The bulk of the vinyl itself is relatively compliant, and i understand the best model is not a point source for the stylus, because it is rotating. It likely behaves far stiffer than a point source stylus model would suggest.

Ultimately all of the groove deflection force that moves the stylus is transferred through the bulk of the vinyl, mat and platter, and ultimately the spindle bearing. Newtons 3rd and all that. But compliance of that system is likely to be very stiff, because of the area involved.

Nevertheless, I agree there is a difference between top surface (mat) damping, and under surface platter damping. Mats often influence sound in fairly subtle ways, and I don't know whether that is via platter damping, or altering sylus/mat/platter compliance model.

[Ldg]

Is this the best way to solve any rumble or is there a better option? I am thinking of using a thick Technics mat on the platter to help damp any noise is this a good idea?

Hi CL, its such a beautiful, vintage TT. Personally, I would see how it performs as it was originally intended. You can likely get idler wheel restoration advice over on the idler forum, but damping the platter seems too late a way to tackle idler rumble, IMO. There would always be artifacts. Personally, I would fix only things which are objectionable and/or not characteristic of the original. Mats generally are a very good way to control platter vibration, and easy to try. Alec is a mat man, worth a PM perhaps ?

[Alec124c41]

If you have noise from the motor, service the motor, and possibly modify the mounts.
If the idler is causing noise, lubricate the bearings, and make sure it is round and soft.
If you have noise from the platter bearing, clean and lubricate it.
There are many ways to damp a platter, including the mat.
The mat does have an influence on the record, apart from it's platter damping. My personal preferences are for the stiff rubber, leather, or cork, over the soft rubber or felt mats, which I feel muddy the bass.
Experiment.

Cheers,
Alec

[johngordon]

The Original Poster, JBonner, wrote:

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.

If you have ever played with a singing bowl you would know that a mat has almost zero influence on its ringing. I would imagine that the influence of a mat is on the record not the platter unless it is heavy, bonded and lossy, and covers the sides also, especially if the platter is in any way bell shaped, (ie has a rim )

Latex is elastic, rubbery, not ideal.

JBonner : if you actually have a singing bowl, play with that - use blue tak -see where the resonance is attenuated and where it is not.

Position your deck sensibly to reduce airborne vibration. Reduce motor vibration, Reduce structure-borne vibration. In other words, generally, reduce the effects, then deal with the residue.

Hardwoods in general, and softwoods, especially spruce, are good for making musical instruments. The corollary of that is if you want your hifi to be a musical instrument, use wood. Metals make good musical instruments too. Unfortunately they are also good for making things. All sad but true.

Plywood makes poor musical instruments. Plastics and composites even worse.

So, perhaps the moral is: make your hifi from plastics, (then make it look acceptable.... )

Don't use lead, unless you have no children and approve of lead in paint and lead in your plumbing.. The Romans used lead plumbing - they gave us the symbol for it - but look at what's become of Italy today...

Berlusconi!

John

[cats squirrel]

good one, John, but the singing bowls vibrate around their periphery, so a dab of blutack here would have a great effect.

And some musical instruments are made of plastic, I have a perspex recorder, and although I haven't used it on stage (although I have used a recorder in an Irish band to play in a key that wasn't D or G) it still has a useful tone.

But I'm making light of a very valid point, one that I have said myself a few times, if you can make a musical instrument out of it, it isn't going to pass muster as a plinth material (or loudspeaker panel). Having said that, I think someone made a harp out of panzerholz, (*%&&^$£!!) but I don't know how much the wood in a harp helps (or hinders) the sound.

[johngordon]

CS

singing bowls vibrate around their periphery, so a dab of blutack here would have a great effect.

Yes, this is the point - that the shape is important - and it is useful to experience that, given that most platters are variations on just a few themes.

And some musical instruments are made of plastic, I have a perspex recorder....

Does a recorder count?

I think someone made a harp out of panzerholz

For the more structural aspects - frame, back, - it might be ok, but as a soundboard who knows - they're usually spruce.

But you have given me an idea. You said:

if you can make a musical instrument out of it, it isn't going to pass muster

In which case surely a banjo would be perfect as a turntable.....?

Come to think of it, there are a lot of banjo-looking decks out there...
J

[Ldg]

If you have ever played with a singing bowl you would know that a mat has almost zero influence on its ringing.

Hmmm. Bowls and platters are sort of cousins. Bessel functions are probably key to describing their resonant behaviour in both cases, especially rim resonances. And in which case, one wonders wherther CL's lead rim band was indeed a 2fer, or even primarily for damping.........?

There's no question that mats have a damping effect on platter resonaces, on the whole. That's not to say there aren't certain resonant modes that might be poorly addressed by mats, of course.

Lead, indeed, is a toxic substance. It's not that I'm advocating using it, merely illustrating flaws in CS' damping analysis and material figures !

Could one make a lead banjo skin sound ? Or a lead guitar sound board ? Probably not. And that's a big clue. The good news is, it would also be too heavy to test. Thankfully ! I always wanted to play lead guitar

[cats squirrel]

these people: http://wikis.controltheorypro.com/index.php?title=Hysteretic_Damping
say the damping value for lead is much lower than mine. Don't forget, these are 'standard values'. yea, right.

So higher, or lower?? Good game...........