Any suggestions for internal damping of a square section carbon fibre tonearm tube?
It obviously should add minimal mass but provide effective damping of tube modes. Mass considerations and routing of internal wiring, make a fully filled tube undesirable. I am thinking of a thin extensional damping layer that can be applied in a low viscosity liquid form to the tonearm laying perfectly horizontal. The ends can be partially blocked to contain the fluid but allow it to cure. The tube is then rotated through 90 degrees and the process repeated until all 4 walls are internally coated.
I have no experience which suggest a free flowing liquid that cures to an effective damping layer.
A concern is that the fluid be fully cured and not chemically damage the carbon fibre resin.
The armtube will not be short so the mass concern is important.
It obviously should add minimal mass but provide effective damping of tube modes. Mass considerations and routing of internal wiring, make a fully filled tube undesirable. I am thinking of a thin extensional damping layer that can be applied in a low viscosity liquid form to the tonearm laying perfectly horizontal. The ends can be partially blocked to contain the fluid but allow it to cure. The tube is then rotated through 90 degrees and the process repeated until all 4 walls are internally coated.
I have no experience which suggest a free flowing liquid that cures to an effective damping layer.
A concern is that the fluid be fully cured and not chemically damage the carbon fibre resin.
The armtube will not be short so the mass concern is important.
I have used light weight open cell foam. I slit the length of the foam with a razor for the tonearm wiring. Silicone spray to help the foam into the tonearm. You don't need to fill the entire length of the tonearm.
I’ve used (as part of a rewire kit) a square cotton pad like those used for makeup removal. Merely placed into the arm, it worked very well.
As for a liquid to schmoo around the tube, I’d look into a silicon RTV of some sort, something like automotive gasket material or sealant, but thinned out so it would flow as you suggest.
As for a liquid to schmoo around the tube, I’d look into a silicon RTV of some sort, something like automotive gasket material or sealant, but thinned out so it would flow as you suggest.
Without measuring the magnitude of damping or increase in vibration magnitude across the frequency range of interest this really becomes a matter of faith and expectation bias versus real engineering. I would suggest that whatever you do, you should be able to undo it!
My only expectation thus far is that some damping will be better than none. Untreated samples suspended from fishing line reveals ringing but the CF is subjectively lower pitched and much better damped than aluminium.
My question is in hope of obtaining shared information about some real world experiences. This could save me much time and effort.
I do intend to record the best results and run them through Audacity spectrum analysis.
Attachments
An assembled arm acts nothing like a free hung tube. Carbon is so stiff that applying 'soft' damping does next to nothing as the impedance difference between the two is so great the vibration barely gets the chance to cross over the material boundary.
Putting a thin Teflon tube in it, wrapping the ends on the outside and using spray foam internally and carefully removing the excess is pretty good, it'll remove the cavity resonance at least.
Putting a thin Teflon tube in it, wrapping the ends on the outside and using spray foam internally and carefully removing the excess is pretty good, it'll remove the cavity resonance at least.
Your comments seem to agree with my experiments on platter/mat/LP interfaces.
https://www.diyaudio.com/community/threads/lp-mat-platter-interface.366676/
I subjectively prefer a platter/mat/LP interface that measurably increases the stylus/groove reaction force, which sends more energy into the tonearm. The intention is that the tonearm mounting efficiently couples to the plinth, which is designed to dissipate energy.
Any suggestions for spray foam? There used to be a product called Space Invader that cured very stiff.
Permatex Windshield Sealant.
Comes in a tube.
Flows like thin molasses, sets in a 1 to 2 hours, stays very flexible like soft jelly-like silicone rubber.
Can be brushed on surfaces too, and tends to follow gravity when still "wet".
I've used it to re-seal cloth surrounds on woofers, and damp edge resonance on paper accordian surrounds.
Comes in a tube.
Flows like thin molasses, sets in a 1 to 2 hours, stays very flexible like soft jelly-like silicone rubber.
Can be brushed on surfaces too, and tends to follow gravity when still "wet".
I've used it to re-seal cloth surrounds on woofers, and damp edge resonance on paper accordian surrounds.
Hi Bon,
I have no suggestions as to what type of material could be inserted into a tone arm tube. However, I would insert two small diameter lightweight tubes into the foam etc. to house the signal wires. I inserted six lengths of cotton pipe cleaners into my own tone arm designs but have no idea as to whether doing so had any positive effect on sound quality.
Sincerely,
Ralf
I have no suggestions as to what type of material could be inserted into a tone arm tube. However, I would insert two small diameter lightweight tubes into the foam etc. to house the signal wires. I inserted six lengths of cotton pipe cleaners into my own tone arm designs but have no idea as to whether doing so had any positive effect on sound quality.
Sincerely,
Ralf
I used powdered cork, extremely light. Then make small plugs of Mortite for each end. You can always pour the cork out and remove the plugs and have your stock arm tube. I used this in a diy Schroeder arm tube using aluminum arrow shaft and it worked great.
Good luck.
Joe
Good luck.
Joe
And to think..... all those wine corks that I tossed in the trash.....
I could have ground them up and went into business stuffing tonearms for the obsessed nervous audiophile crowd!
I'd advertize it as "Quantum Tube Damping"!
And made a hefty retirement fund at the same time.
I could have ground them up and went into business stuffing tonearms for the obsessed nervous audiophile crowd!
I'd advertize it as "Quantum Tube Damping"!
And made a hefty retirement fund at the same time.
That sounds worth trying. I like the fact that it is reversible, non-toxic, biodegradable, yada, yada.
Looks like I will have to open some of the good stuff. 99% of my wines are in screw tops.
Hi,
when building my 12" arm, I had the same Q about sone form of damping.
Eventually I used 3 small slices cut about 1mm thick from ear protector foam pads (those little cone thingies).
While sq225917 is right in theory, at least in my practical case the three small discs of foam had a surprisingly large and good effect.
I used a small tube, compressed a single foam disc and inserted it into the tube end.
Then I inserted the tube into the arm tube und 'released' the foam disc at the wanted position by pushing it with a wooden pin out of the tube.
The foam expands and the discs remain fixed in their positions about 1/4, 1/2 and 3/4 of the arm tubes length.
I think that the mild pressure of the foam against the arm wand is mostly responsible for the damping effect.
Before inserting the foam discs I pulled the two cable strands through the arm tube and fixed them temporarily with tape on the outside such that the cables remained 180° opposite each other on the inside of the arm wand.
The expanding foam discs softly but securely fixed the cabling.
Tapping the arm wand with a metal pin now produces a well damped 'thugg' sound instead of a brighter 'tigg' sound before.
This method is not only cheap but reversible and scalable and adds very low mass.
Just try and add or subtract as many foam discs You think are required.
jauu
Calvin
when building my 12" arm, I had the same Q about sone form of damping.
Eventually I used 3 small slices cut about 1mm thick from ear protector foam pads (those little cone thingies).
While sq225917 is right in theory, at least in my practical case the three small discs of foam had a surprisingly large and good effect.
I used a small tube, compressed a single foam disc and inserted it into the tube end.
Then I inserted the tube into the arm tube und 'released' the foam disc at the wanted position by pushing it with a wooden pin out of the tube.
The foam expands and the discs remain fixed in their positions about 1/4, 1/2 and 3/4 of the arm tubes length.
I think that the mild pressure of the foam against the arm wand is mostly responsible for the damping effect.
Before inserting the foam discs I pulled the two cable strands through the arm tube and fixed them temporarily with tape on the outside such that the cables remained 180° opposite each other on the inside of the arm wand.
The expanding foam discs softly but securely fixed the cabling.
Tapping the arm wand with a metal pin now produces a well damped 'thugg' sound instead of a brighter 'tigg' sound before.
This method is not only cheap but reversible and scalable and adds very low mass.
Just try and add or subtract as many foam discs You think are required.
jauu
Calvin
The thing about using foam....
Over time, it dryrots, becomes stiff, and crumbles.
Then you've got a jiggly mess of crumbed rotten foam in the tonearm.
Not a good thing.
Better to use as mentioned the cork, or my suggestion of flowable silicon gasket sealer, used sparingly.
Over time, it dryrots, becomes stiff, and crumbles.
Then you've got a jiggly mess of crumbed rotten foam in the tonearm.
Not a good thing.
Better to use as mentioned the cork, or my suggestion of flowable silicon gasket sealer, used sparingly.
If you haven't read http://korfaudio.com/blog, you might find it of interest, he states
"Added viscous damping is lethal to sound quality"
He has lots of measurements on arm tube resonances
the reason I mentioned melamine foam is its very light and you said mass was an issue. I won't dry out as it has no volatile softening agents etc, and if you compress it, it springs back but is much softer.
regards
james
"Added viscous damping is lethal to sound quality"
He has lots of measurements on arm tube resonances
the reason I mentioned melamine foam is its very light and you said mass was an issue. I won't dry out as it has no volatile softening agents etc, and if you compress it, it springs back but is much softer.
regards
james