Damping Platter With Liquid Latex

[Ldg]

Yes, agree, wordwizard. Except that it's not me who runs tests on damping materials, that's CS ! I'm the one who reckons CS' methods aren't yielding credible material damping figures right now anyways. I only go round hitting things with mallets on very special days.

[wordwizard]

Yes, agree, wordwizard. Except that it's not me who runs tests on damping materials, that's CS ! I'm the one who reckons CS' methods aren't yielding credible material damping figures right now anyways.

No problem... I just thought that in order to make the tests "repeatable" all the variables needed to be taken into account. Striking force and where struck are certainly variables.

I only go round hitting things with mallets on very special days.

And those are?

[cats squirrel]

basically me

the investigation into damping factors does not require that the material (object) be struck a consistent blow, all that is required is a clean strike (no bounce). Even so, it is possible to get within 10% amplitude from hand held hammer blows.

And the frequency dependency thing is well known, as is the temperature relationship. I have measured both. What should be mentioned is that different materials are affected to different degrees by temp and frequency., some to a large degree, others less so.

[Eoin]

When I was striking the undamped platter, the way tones develop reminds of a gong/cymbal somewhat.

Just one observation:

If testing with different dampening materials, you should develop a method to consistently deliver the same striking force at the same place in the platter.

That would remove one variable from your equations.

I still don't think this is necessary... A soft tap or a hard tap.. Does it make any difference to looking at damping. You are looking at how quickly a pulse dies away, are you not?

[Rap]

When I was striking the undamped platter, the way tones develop reminds of a gong/cymbal somewhat.

Just one observation:

If testing with different dampening materials, you should develop a method to consistently deliver the same striking force at the same place in the platter.

That would remove one variable from your equations.

I still don't think this is necessary... A soft tap or a hard tap.. Does it make any difference to looking at damping. You are looking at how quickly a pulse dies away, are you not?

A larger pulse will take longer to decay just as a bell that is struck harder will sound louder and longer.

[Eoin]

I'd need to check the maths but I think the time taken for it to decay to a proportion of it's peak will be the same regardless of a high initial peak or a lower one. I havent got a reference but perhaps I'll have a look. You should find that the time for any pulse tondecay to half of it's value (or any proportion) will be the same.

[Ldg]

I'd need to check the maths but I think the time taken for it to decay to a proportion of it's peak will be the same regardless of a high initial peak or a lower one. I havent got a reference but perhaps I'll have a look. You should find that the time for any pulse tondecay to half of it's value (or any proportion) will be the same.

Yes, that's correct maths, Eoin.

However......back to the cymbal analogy, plainly different things happen according to how hard a cymbal is struck. Again, its a difference between simple models and what really goes on that is interesting. Many and various vibration modes have different decay rates, spectra, and damping. All wrapped up into the same cymbal. One material. Behaviour determined by structure.

I also hate damping good cymbals, BTW. But as an illustrative point, one can alter tone and shape specific resonances without affecting overall decay time, with application of certain type of damping. Generally for the worse, I agree, JL. Same could well be true of good platters. It's not a bad analogy, perhaps.

And the frequency dependency thing is well known, as is the temperature relationship. I have measured both.

No, the way you are measuring material damping factor is flawed, catsquirrel, and hence significantly frequency dependant. Standard material property definitions are not frequency dependant, intentionally so. And of course certain material properties change with temperature, sometimes significantly. It's not that damping does not play a part in what you are measuring, it's just not a defining or unique part, and other factors equally apply.

[cats squirrel]

A larger pulse will take longer to decay just as a bell that is struck harder will sound louder and longer.

but the rate of decay will be the same, so it will have the same damping factor. As it will the same log decrement. Pulse height is not important, unless the signal captured is overloading the recording device.

LD, you keep going on about standard properties, what do you mean by this. Do you mean intrinsic properties? Standard property has no scientific meaning.

With the exception of a few seemingly fundamental quantum constants, units of measurement are essentially arbitrary; in other words, people make them up and then agree to use them.

An intrinsic property is an essential or inherent property of a system or of a material itself or within. It is independent of how much of the material is present and is independent of the form the material, e.g., one large piece or a collection of smaller pieces. Intrinsic properties are dependent mainly on the chemical composition or structure of the material.

[Eoin]

The more I think about this the more I wonder if it's not relevant, or of little use certainly for a platter. If damping can muffle down a struck bell, but does not attenuate a constant input (unlike a fluid fought on the arm) then is it going to help us?

I think I'll get a book out and do a little reading. Clearly a complex subject and if efforts are to be expended in reducing unwanted sound or vibrations in a deck then it is of course nice to know what's effective and what's a dead end. Reduction of noise incident to the whole system, attenuation of noise present, isolation of noise to the cartridge.

Not easy stuff!

[cats squirrel]

Eoin, don't forget, the platter will only ring if made to do so, it will not start ringing on its own.

When I was measuring the ringing (or not) of a platter, I was listening to the radio in the background. To my surprise, I could hear the radio sound on playback of the recording, but the tone from the ringing platter was at a far lower level (less than vinyl roar).

So I would say that reducing the impact of loudspeaker generated sound is far more important than damping a platter, especially as I see many systems where the tt is next to a 'speaker. If this is how people listen to vinyl, then trying to get rid of minutia is like pushing the round object up hill.

[Rap]

A larger pulse will take longer to decay just as a bell that is struck harder will sound louder and longer.

but the rate of decay will be the same, so it will have the same damping factor. As it will the same log decrement. Pulse height is not important, unless the signal captured is overloading the recording device.

The rate yes but not the time line.

[Rap]

So I would say that reducing the impact of loudspeaker generated sound is far more important than damping a platter, especially as I see many systems where the tt is next to a 'speaker. If this is how people listen to vinyl, then trying to get rid of minutia is like pushing the round object up hill.

Show us a picture of "Darwin"

[duficity]

anyone use JB Weld as a platter filler material to decrease resonance and increase weight. It would seem to be a suitable material and is certainly dead sounding.

[wordwizard]

anyone use JB Weld as a platter filler material to decrease resonance and increase weight. It would seem to be a suitable material and is certainly dead sounding.

It would work if you had a lathe to shave off the lumps and a means of balancing the platter again.

Otherwise any gains made in mass will be negated by speed fluctuations and excess bearing wear from the unbalance.