Damping Platter With Liquid Latex

[Ldg]

Hi CL. I would leave the lead ring, because it is bona fide. Platter damping is generally well accomplished by mats, and that would be a good place to start, especially as it again preserves the bona fide nature of the TT. If it ain't broke, don't fix it. What was it originally fitted with ?

Plinths are strictly off topic. But much depends on whether you are trying to add colouration or not. If so, it's best to use dimensions and materials that are already proven 'good' with that specific TT. It's unlikely you will be able to find, by trial and error, an optimal solution in a reasonable number of trials. Because your TT is rare, that might be hard, but you never know, someone might already know. If avoiding colouration is the aim, then absolute minimalism is best IMO. How few structural pieces, and how simple can they be made. Because then, if you don't like it because of spot resonances the number of vibration modes is far simpler to address and damp, and generally more intuitive.

HTH! And appologies again for my part in the off topic drift.

[cats squirrel]

This was an interesting thread and IMO it has been spoiled for 'Point making'. Can we stop please and get back on topic??
Cats what is your opinion on the lead ring and a Technics rubber platter mat and the plinth is to be a huge Aus hardwood plinth, any ideas are appreciated (for my Commonwealth of course).
Regards
CL

getting back OT:

LD's point is a valid one, it may be authentic, but I don't think it will add (or subtract) much to the final result, and it is a nasty substance, especially any dust it may create. Personally, I would chuck it, or at least take if off, pending. You may find it necessary, but I doubt it.

The hardwood plinth is more of a problem. Hardwood (as a generalization, I haven't much experience) is not good at damping, especially in the bass and mid frequencies. Other materials will provide a less resonant alternative, something with intrinsic damping. If you tell me what your preferences are (wood, metal, ceramic, plastic, composite) then I could suggest some ideas.

[Rap]

so accelerometers go up to 5MHz do they?

And does this mean that when HiFi World measure the resonances in tone arms with their B&K accelerometer, they do so in a sound proof room, with air pressure regulation, free of air tremour and so forth? I think not!



The tests I do are straight forward to do, anyone could do them, and give good enough results to be useful. Call it pseudo-science if you like, but it is helping a lot of people, who seem happy. I could not wish for more. And I have talked to and helped some very good people, some of whom make HiFi components which have won awards (whatever that means).

I'm not answering any more of your idiotic rhetorical attempts to fluff over your mistakes Bryan. Twisting words and rhetorical b.s again!
The numbers posted in regards to acoustic impedance's of materials is measured in ultrasonic, what does that have to do with mechanical resonance as measured by Hifi World and how does that validate your comment that ´ultrasonic measurements bear no relation to other sonic and waves'? Just answer that if you can or any of the other comments made with out wandering into other subjects and theories.

The formula I use was probably not from anything you gave me. The equations are straight forward (even the one I eventually used had a small mistake in it, now corrected by me).

What formula is that? or should I notify the Nobel comity that you are up for a prize having turned the laws of physics on their head? Or maybe your "correcting" of formulas explains what ld was hankering after in suspecting your methods and conclusions.

No, it works well enough, and easily showed the difference between two batches of resin used in making your bentonite/resin mix. People, especially engineers, seem to get carried away with numbers, rather than what those numbers represent.

Yes you recived a sample of my resin-bentonite mixture (not from me I might add) but the mixture was made to my exact recipe Right down to grain distribution/size and charge of bentonite and the exact type of resin to be used. You then fuddled around trying to understand it's properties and trying to improve on it using same or similar materials before posting my original recipe on your website when you couldn't do so. (with out my consent) You then grudgingly mentioned my "help in development" much later, but only after I argue with you like usual about what constetuted a discovery, invention ect and that you were accrediting others with their input (but mostly your self) otherwise I wouldn't even have gotten a mention. I think this kind of sums up your "scientific rigour" and generous self-less "helping of others"

The Bento/poly mix was concieved of, measured, developed and perfected with out any of your input and I looked at your "measurements" of it's mechanical resonance and damping as just another objective observation.
It was developed for a specific purpose taking into special account acoustical impedance in relation to acoustical damping and matching to other specific materials I was researching and utilising at the time. Like lead.

As to getting carried away with numbers I quote you from a former post citing one of your instructors "why spend 30 minuets at the library when you can spend 3 months in the laboratory?" You were referring to those who at the time were building plinths without exploring the physics behind it. Bryan it's about time you popped of to the library for a quick 30 minutes. Especially if your going to keep trying to come across as some sort of authority on this whole subject and not in the least if you are offering your "measuring" services to others for a nominal fee.

[JaS]

[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

[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