no. Don't use lead for anything. It is not a user/environmentally friendly material. And it doesn't damp,although the best of the metals. It is not viscoelastic, bend it, and it stays bent!
There are a few things which, when made as a composite, do have a reasonable damping factor, and its not easy to choose which ones. They all have to be measured!
Acrylic/mdf works quite well, as, I think, acrylic over chipboard. My Michell Focus 1 has the latter!
Guessing which materials in combination might be good no longer works for me, I'm about right 50% of the time, so pure guesswork, really!
There are a few things which, when made as a composite, do have a reasonable damping factor, and its not easy to choose which ones. They all have to be measured!
Acrylic/mdf works quite well, as, I think, acrylic over chipboard. My Michell Focus 1 has the latter!
Guessing which materials in combination might be good no longer works for me, I'm about right 50% of the time, so pure guesswork, really!
Cats Squirrel,
Several months back, I was really impressed with the sound of a very expensive Turntable made by Acoustic Solid. It had an Acetal platter, but the record was not directly on the platter. Instead, it had several other layers (leather, metal and acrylic) between the platter and the record. I'm guessing they were creating the mechanical mismatch you describe. Would you agree?
Hugh
depends, Hugh. If the layers are glued together, a laminate is made (called a glulam). That will have its own set of properties. This is something people will have to remember, but the more layers, the thicker the composite, the higher the resonance frequencies, the lower the critical frequency.
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I would argue that the damping requirements of a turntable platter is very different to those of a plinth.
A plinth should dissipate undesirable mechanical energy from the turntable bearing, motor and tonearm resonances.
I have found resin/bentonite to be the best material I have used for this purpose. Cats Squirrel has repeated ad nauseam that the evidence in favour of constrained layer plinth construction is dubious.
When it comes to platters, the principal unwanted input are the stylus-groove reaction forces.
The groove is responsible for pushing the stylus in a motion replicating the input signal. The groove walls experiences an opposing force. Assuming an intimate contact between LP and platter, the LP/platter experiences this reaction. The smaller this is, the less reaction energy interacts with the LP/platter, potentially exciting resonances which contaminate the desired stylus motion. The remaining reaction energy is transmitted via cartridge/tonearm and is preferentially dissipated by the plinth.
In another thread, I investigated the level of LP/platter reaction energy induced by an impulse.
LP mat/platter interface
On my experiments the Acetal/POM/Delrin platter incurred the least impulsive LP/platter energy transfer compared to a conventional rubber damped aluminium platter with a variety of mats. The results were audible in the dramatic superiority of the Acetal/POM/Delrin based platter on low level detail.
Bon quote " Cats Squirrel has repeated ad nauseam that the evidence in favour of constrained layer plinth construction is dubious."
Maybe the ad nauseam is necessary. Constrained layer damping is a damping technique, it is not a construction. Several layers of the same material (like ply) or disparate materials is called a glulam, a contraction of the term glued laminate. This has been known for well over a century. It does not improve matters, in fact it makes matters far worse, as far as plinth duty is concerned.
As regards platter and record damping, the two will always be inextricably linked. Platter damping has to deal with vibrations coming from the tt support, plinth and tt mechanicals. The platter mat should deal with the vibrations from all of the above PLUS those from the record itself, vibrated not only from the stylus, but from the sound in the room (from the loudspeakers). It has two jobs to do, so a construction to deal with each would seem sensible. Getting the right mechanical impedances would seem to be a step in the right direction. But gluing several disparate materials together, ad nauseam, (although this can produce something useful) is not a universal panacea.
Maybe the ad nauseam is necessary. Constrained layer damping is a damping technique, it is not a construction. Several layers of the same material (like ply) or disparate materials is called a glulam, a contraction of the term glued laminate. This has been known for well over a century. It does not improve matters, in fact it makes matters far worse, as far as plinth duty is concerned.
As regards platter and record damping, the two will always be inextricably linked. Platter damping has to deal with vibrations coming from the tt support, plinth and tt mechanicals. The platter mat should deal with the vibrations from all of the above PLUS those from the record itself, vibrated not only from the stylus, but from the sound in the room (from the loudspeakers). It has two jobs to do, so a construction to deal with each would seem sensible. Getting the right mechanical impedances would seem to be a step in the right direction. But gluing several disparate materials together, ad nauseam, (although this can produce something useful) is not a universal panacea.
in that case, Hugh, that may be the case. However, using materials that damp would be my choice, and as metal doesn't damp much, and acrylic only slightly, and I don't know about leather, it would seem there is room for improvement.
Be careful about citing Acetal, as it is often confused with Delrin. (Even suppliers have problems!). One has a damping factor about 10 times that of the other, but which is which?
Be careful about citing Acetal, as it is often confused with Delrin. (Even suppliers have problems!). One has a damping factor about 10 times that of the other, but which is which?
Bon,
That's an interesting thread.
Have you ever tried a leather mat? At the suggestion of a Pal, I tried a $30
2mm one on a Rega glass platter and a Heybrook Aluminum platter. Great on both.
I've purchased a Delrin platter from Tangospinner for my DIY TT. Looking forward to that one.
Hugh
The literature on that TT (Wood Refernz) just calls it BOM. Which one has better damping? Acetal or Delrin?
Leather seems really good for snuffing out the ringing of glass and aluminum platters.
Thanks,
Hugh
I have a Delrin Platter and some 3/8" pieces of Acetal. I think I'll be getting out the Accelerometer and hammer soon.
Here's a link for the Leather Mat I bought in case anybody wants to try one...
Genuine Leather Turntable Mat | eBay
Here's a link for the Leather Mat I bought in case anybody wants to try one...
Genuine Leather Turntable Mat | eBay
Wow, that is quite a difference in DF. What I used was described as Acetal/POM, so was much cheaper than the DuPont branded Delrin. My impulse experiments measured only the potential energy return from a peripheral ring plus centre weight loaded LP subjected to a dropped marble and steel ball bearing. This varied from 5% with a carbon graphite mat to 80% with an acetal/SS platter. I don't know what is the precise correlation between DF and impulse energy return. The carbon graphite has a fine porous structure.
POM is made in two types, a homopolymer and a co-polymer, which will have different properties. If testing for damping factors, remember that, like most man-made materials (and natural ones, too!) there will be batch to batch variabilities, so don't be surprised if you get different results to mine, but one should be better than the other! And, for example, wood will vary quite a bit, even wood from the same trunk!
The 'Link' is a Dupont description of the differences between
Acetal POM and Acetal POM-H.
A Google Search will show up other sites that discuss the differences between the two materials.
In general the applications for the materials are similar, one has a increased porosity, which could discount it from certain uses as a part in production machinery.
How the two differences in basic make up will be seen on a
Damping Measurement Recording of Data and if this is a difference that can be detected as improved through a Audible Assessment, is possibly still awaiting the combined trials for each material.
Acetal Copolymer Alternative | Homopolymer vs Copolymer
I am at present becoming interested in the Tufnol Brand Materials -
Carp Brand (Cotton Compression) and Kite Brand (Paper Compression).
Is there any testing known of for Damping or Audible Assessment for these Materials ?
Acetal POM and Acetal POM-H.
A Google Search will show up other sites that discuss the differences between the two materials.
In general the applications for the materials are similar, one has a increased porosity, which could discount it from certain uses as a part in production machinery.
How the two differences in basic make up will be seen on a
Damping Measurement Recording of Data and if this is a difference that can be detected as improved through a Audible Assessment, is possibly still awaiting the combined trials for each material.
Acetal Copolymer Alternative | Homopolymer vs Copolymer
I am at present becoming interested in the Tufnol Brand Materials -
Carp Brand (Cotton Compression) and Kite Brand (Paper Compression).
Is there any testing known of for Damping or Audible Assessment for these Materials ?
these are the damping factors for the ones I have tested:
Tufnol Carp brand 0.169 @ 509 Hz
Tufnol IP/13 0.020 @ 903 Hz
Tufnol Kite brand 0.026 @ 465 Hz
Tufnol Whale brand 0.046 @ 948 Hz
It would seem only the Carp brand has any chance of light damping.
As regards audible assessment, I have my own ideas. I know it will be controversial, but I believe some people (maybe most) actually want a little distortion to enjoy their music. How much is the big question, and probably is different for each person, or music genre, or both. So I would conclude that although it is easy to say which materials will have the most damping and which will have the most 'lively' sound, choosing which ones for each person will prefer is impossible, I would think!
Tufnol Carp brand 0.169 @ 509 Hz
Tufnol IP/13 0.020 @ 903 Hz
Tufnol Kite brand 0.026 @ 465 Hz
Tufnol Whale brand 0.046 @ 948 Hz
It would seem only the Carp brand has any chance of light damping.
As regards audible assessment, I have my own ideas. I know it will be controversial, but I believe some people (maybe most) actually want a little distortion to enjoy their music. How much is the big question, and probably is different for each person, or music genre, or both. So I would conclude that although it is easy to say which materials will have the most damping and which will have the most 'lively' sound, choosing which ones for each person will prefer is impossible, I would think!
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cats squirrel
Thank You for the information, so Carp looks like it could be used for an
attenuation purpose in a assembly of materials arranged for this purpose.
As for each individual having a uniqueness in their preferences for how a audible sound is received and perceived, you are on the Money.
I have heard very coloured bass notes that I am very sensitive to, and are very quickly notice as being a detractor, being classed as a very impressive bass presentation by another.
I have spent many hours producing differing configurations of materials and devices to attenuate a sound that has a Harmony with my own preferences.
This will remain a ongoing exercise, as I find the varieties of methods that can be used to manage energy, a enjoyable extension of my Enthusiasm for Music Replays.
The Audible Variables that can be discovered are quite something and once the preference is discover for the individual there is a road of no return being entered.
A recent experience of seating a Pre Amp that has a Harmonic Component in the Circuit proved quite valuable.
When investigating a method to manage a 5Kh Harmonic that is produced by the Pre Amp.
During the experience, a few configurations of Sub Plinth Materials were used.
When using a method that had a Sub Plinth of a Permeable Aerated Soft Foam, the end result, produced a remarkable effect as an alternative to a Hard Board Foam that was used for the same purpose, and thought to be the better of other material selections.
Combining the Two Foam Materials both had the capability to produce a further but subtle variation of the extremes of each.
I am using the Soft Foam, on top and under the chassis, that is where I found the cut off point to my preferences.
Thank You for the information, so Carp looks like it could be used for an
attenuation purpose in a assembly of materials arranged for this purpose.
As for each individual having a uniqueness in their preferences for how a audible sound is received and perceived, you are on the Money.
I have heard very coloured bass notes that I am very sensitive to, and are very quickly notice as being a detractor, being classed as a very impressive bass presentation by another.
I have spent many hours producing differing configurations of materials and devices to attenuate a sound that has a Harmony with my own preferences.
This will remain a ongoing exercise, as I find the varieties of methods that can be used to manage energy, a enjoyable extension of my Enthusiasm for Music Replays.
The Audible Variables that can be discovered are quite something and once the preference is discover for the individual there is a road of no return being entered.
A recent experience of seating a Pre Amp that has a Harmonic Component in the Circuit proved quite valuable.
When investigating a method to manage a 5Kh Harmonic that is produced by the Pre Amp.
During the experience, a few configurations of Sub Plinth Materials were used.
When using a method that had a Sub Plinth of a Permeable Aerated Soft Foam, the end result, produced a remarkable effect as an alternative to a Hard Board Foam that was used for the same purpose, and thought to be the better of other material selections.
Combining the Two Foam Materials both had the capability to produce a further but subtle variation of the extremes of each.
I am using the Soft Foam, on top and under the chassis, that is where I found the cut off point to my preferences.
no. Don't use lead for anything. It is not a user/environmentally friendly material. And it doesn't damp,although the best of the metals. It is not viscoelastic, bend it, and it stays bent!
There are a few things which, when made as a composite, do have a reasonable damping factor, and its not easy to choose which ones. They all have to be measured!
Acrylic/mdf works quite well, as, I think, acrylic over chipboard. My Michell Focus 1 has the latter!
Guessing which materials in combination might be good no longer works for me, I'm about right 50% of the time, so pure guesswork, really!
HI,
I made 3 TT plinth in the last years:
Thorens TD 160 using solid Mahogany wood and small leads glued. Th plinth weighted 17 Kg alone. It sounded pretty good to me comparing to the previous plinth. When I finally sold it I regretted it, though the short coming of Thorens was the too loosen and ratting a bit.
The second plinth was made for a friend and was a direct drive TT. He wanted cheap so I used MDF and separated the tone arm base from the plinth. In my ears did not sound as alive as the other.
The third one is a Belt Drive TT, floating type by mag lev, plinth by birth ply of two types, one softer one harder alternated in layers. I have made in each plane of the plinth holes and inserted small recycled leads glued as well.
Harm board is made on Mahogany solid wood attached to the aluminum floating part.
Platter is in Acrylic 320mm diameter and 4.3 Kg, the project was based a lot around the acrylic platter and I still happy to have used it. Put is needed and mine is made in acrylic and stainless 316, weight 500 grams. I do not use any mat on the platter, I would like to try a copper one but never did so far as a bit costly.
Bearing is a standard one oil lubricate with bronze bushes, sphere at the bottom 5mm and bronze thrust pad. Bearing shaft 13mm highly polished and very precise in the bushes.
As forth plinth I have plan to make a Lenco L 75 projects as I have 2 Lencos TT in the garage and the idea is:
Tonearm pod separated from the plinth with a combination of different material. I know it is a controversial discussion the separated or not TA pod.
Plinth made as a thick butcher way, again with solid Mahogany wood, leads and glue in a precise part and point, motor unit fixed in the bottom part with a special frame support ( not upper plate ) and separated from the bearing plate.
I know leads are not so friendly, but I recycle what is available and not use new ones ( better use them in my TT that in the guns ).
All above is in my mind still as now I am struggling with other issue in the third TT.
Rgds
Adelmo