only vaguely, mate, and I have mislaid my spreadsheet for two layer materials!
Try something like 12mm mdf with 5mm acrylic, but no idea what would go with 10mm acrylic.
The thicker the material, the stiffer it is, the higher the resonance frequencies and lower the critical frequency. So the frequency range between these two (fundamental resonance frequency and critical frequency) will be smaller, and there will be less advantage from the added mass. HTH
Try something like 12mm mdf with 5mm acrylic, but no idea what would go with 10mm acrylic.
The thicker the material, the stiffer it is, the higher the resonance frequencies and lower the critical frequency. So the frequency range between these two (fundamental resonance frequency and critical frequency) will be smaller, and there will be less advantage from the added mass. HTH
I ran some numbers for you, 10mm acrylic facings (two needed) and 12mm mdf. Looks good. Assumed damping was similar to what I measured from the two layer panel.
© cats squirrel 2021
The bump around 200 Hz is the fundamental resonance frequency, and about 1800 Hz is the critical frequency. Note that the data I inputted are mean values for the materials, and actual materials may give slightly different results. HTH
© cats squirrel 2021
The bump around 200 Hz is the fundamental resonance frequency, and about 1800 Hz is the critical frequency. Note that the data I inputted are mean values for the materials, and actual materials may give slightly different results. HTH
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acrylic glue seems good!
I'll run some numbers for you (if spoiler doesn't mind!) regarding ply. Again will mention the parameters I use are mean values for ply, so slight differences may be found.
The different cores don't change the overall picture much at all, with 12mm acrylic and 12mm core. With ply, the critical frequency dips down to 1580 Hz, and only 10dB above baseline, particle board (chipboard) is a little better, with Fc at 1613 Hz and the Fc dip down to 20dB. The latter has better damping in raw form, but unknown as a laminate. HTH
I'll run some numbers for you (if spoiler doesn't mind!) regarding ply. Again will mention the parameters I use are mean values for ply, so slight differences may be found.
The different cores don't change the overall picture much at all, with 12mm acrylic and 12mm core. With ply, the critical frequency dips down to 1580 Hz, and only 10dB above baseline, particle board (chipboard) is a little better, with Fc at 1613 Hz and the Fc dip down to 20dB. The latter has better damping in raw form, but unknown as a laminate. HTH
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a frame plinth. The big problem here is that there is a big difference between a panel (plate) and a frame (clamped beams). However, I have started a frame plinth using ipé wood (df 0.5) where the Lenco plinth sits inside the sides, rather than on top. But I've had problems with gluing the ends together (butt joints) so I've gone with external L-shaped brackets. The edges of the Lenco have square section carbon fibre tubes filled with a damping compound for the top plate to sit on. Base is made of a composite (not disclosing yet!) and this sits on four heavy door stops.
The Lenco main bearing will be clamped to the composite base. Hope this makes sense.
The Lenco main bearing will be clamped to the composite base. Hope this makes sense.
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Sorry, Hiten, I misread your question.
The answer is no, it is not a good idea, because you would have a mix of structures, a composite (with layers glued) and a pile of other bits, which would probably vibrate quite a bit! Mechanical impedance would probably play it's part, too.
Glueing is fine, but it has to be able to allow the structure to flex a little, as flexing helps with the damping. Stiff things don't, as a general rule, damp very much at all.
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either discuss in a sensible manner, Robert, or butt out.
Awww, Bryan, there’s no possibility of discussing anything with you in a reasonable manner, unless one unequivocally agrees with the ‘bullship’ you so generously provide to people who somehow believe you are a materials scientist. People bring up real science, and you get all crusty and defensive (the audio corner of the internet is riddled throughout with your melt-downs). You’ve never had a reasonable discussion: you just take your ball peen hammer and 50x50 samples to the next forum.
I’d love to see your testing methods peer-reviewed (no, not your peers: actual scientists). And i’d really love to witness a DBT of you identifying audible/perceivable differences between millimeters of acrylic. Or panzerholz. Or himalayan kitty litter. I’m
But just for fun, Bryan, have you tested Feinholz? Unlike its sister Panzerholz, it is designed woth acoustic properties in mind, not anti-ballistic properties. Good luck: i eagerly await your results.
oh i don’t mind you running any number you feel like running. I just doubt the veracity of your results so i doubt very much the value of your proclamations.
If people have the materials on-hand and the means to implement them for use in a plinth, given that this is a DIY forum, i suggest they do it themselves and trust their own ears. There are so many ways to achieve great sound, even using materials that at first seem counterintuitive. Systems are exactly that: systems. The interactions are complex, and require holistic thinking. Despite Bryan’s whining, there is no magic formula for audio nirvana through mm-specific super-damping plinths, only that which works best with all the other kit involved. I wonder how many here have heard an American Sound? It’s a massive block of stainless steel with a belt drive. Or a Saskia? It’s a slate-plinthed idler. They both are the best i’ve ever heard. But wait! How can that be?? Stainless steel and slate both ring like bells! (Sic: neither does in these applications). Better throw everything that doesn’t achieve the proper Cats-approved damping factor away and use no more and no less than 25-mm of bullet-proof plywood. Nothing else will work.
And Bryan, you keep going on about some secret material you’ve developed: as far as one can tell, you still have a Lenco drive (very good) without a plinth at all (maybe ok, maybe not) with an RB-250 and an AT95 (both excellent for their price points, but hardly SotA. Your credibility as the plinth material authority would be vastly upgraded if you’d just demonstrated the super matterial you’ve invented.
Cats and misko1989,
Just for fun, I pressed 12mm Acrylic/ 14mm mdf/ 12mm Acrylic together with Ductseal. It's evident that it's damped fairly well.
I'll try an actual glue sometime later. Some of the ones meant for windows and construction adhesive are very stretchy, but not "lossy" like Ductseal or Greenglue.
Hugh
When it comes to Silicone based Sealant that are used in construction, some are used for Sealant Purposes and have adhesive properties and some are adhesives.
In their cured states they will be identified as being Low Modulus or High Modulus.
Low Modulus will maintain a elasticity and require a small amount of force to stretch the dry material.
I have used Low Modulus that has a very easy to compress softness.
A common white Widow frame Silicone will be substantially harder to compress as a comparison but will deform in shape with applied pressure from the hand, especially if a implement is used to indent the material.
I have used High Modulus that can set as hard as a plastic to the touch.
A little bit of soapy water on the surfaces will stop adhesion and a surface degrease will substantially improve adhesion.
In their cured states they will be identified as being Low Modulus or High Modulus.
Low Modulus will maintain a elasticity and require a small amount of force to stretch the dry material.
I have used Low Modulus that has a very easy to compress softness.
A common white Widow frame Silicone will be substantially harder to compress as a comparison but will deform in shape with applied pressure from the hand, especially if a implement is used to indent the material.
I have used High Modulus that can set as hard as a plastic to the touch.
A little bit of soapy water on the surfaces will stop adhesion and a surface degrease will substantially improve adhesion.
misko1989,
I'm guessing this is pricey being a 3M product. If you can get them, 3M does make tapes that stay pliable for vibration purposes, but they are very expensive.
For my experiments, I'm thinking Greenglue and Ductseal are likely just as effective for much less money. Hoping to see if some pliable glues are in the same ballpark.
Hugh
ahh. OK. I think I understand. Need to visit your excellent website again.Sorry, Hiten, I misread your question.
The answer is no, it is not a good idea, because you would have a mix of structures, a composite (with layers glued) and a pile of other bits, which would probably vibrate quite a bit! Mechanical impedance would probably play it's part, too.
Glueing is fine, but it has to be able to allow the structure to flex a little, as flexing helps with the damping. Stiff things don't, as a general rule, damp very much at all.
Regards