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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: Re: Help with DIY Symposium platforms posted by David Aiken on March 5, 2003 at 13:36:05:
Hi David,
My apologies for not including you in the credits above ...you were certainly a main source of information last year."That would result in the platform not only passing low frequency vibration through, rather than absorbing it as intended, but also actually magnifying the low frequency vibration under some circumstances."
....My take was that constrained layer damping required quite different materials for low and high frequency damping. Something like a cork/rubber combo for low frequencies (as used in construction to isolate machinery from floors or the actual floor structure from the wall structures), but something softer and lossier for higher frequencies. So, I am not really attempting to attack lower frequencies with a constrained layer platform, I am putting the inner tube under it (and Rollerblocks above it) for this purpose."I haven't tried black hole but I thought that it was intended to absorb sound waves inside the speaker cabinet and that isn't quite the same as absorbing conducted vibrations."
....yes, open cell foams for soundwaves and closed cell foams for structure borne resonance."...I'd go for aluminium over steel myself, and the ring of aluminium when struck is nowhere near as defined as that of steel which I think is a plus (that's two of the reasons I made my rack out of aluminium). The timber it's glued to will damp the resonance anyway."
....I don't think I have enough info on this yet to decide, or if it even makes a difference (given the damping by the bonding layer and adjacent wood layer as you said). Strangely, Symposium use aluminium on their middle level products, but stainless steel on the bottom level (Svelte) and the top model (Quantum). The SS would be more rigid, and although less self-damped than aluminium, perhaps the external damping eliminates this issue anyway ???I agree with you that we should minimise the mass of the platforms. For this reason, I would tend to go for ply rather than MDF. Some people have used MDF for shelves (eg. on Flexy racks) and found them to colour the sound, but I have not seen any similar complaints about ply. Plus, MDF edges look terrible whereas nicely finished ply edges can look great.
illini_skn mentioned that MDF can warp. If it is of sufficient thickness for the intended load, appropriately supported and sealed (a couple of coats of MDF sealer before top coats) then it shouldn't warp.
A couple of people mentioned the unattractive edges of constrained layer platforms. Dave c suggested "...you could build the MDF or ply layer with a frame to cover the soft inner layers..." and this would look fine. However, I had another idea. How about slightly indenting all the layers between the stainless steel (or aluminium) outer layers. Then wrap a thin vinyl (eg. used for cushions or outdoor table cloths) strip around the platform between these outer metal layers, held in place by contact adhesive ? The vinyl is very flexible (and self damped) and will not interfere with the operation of the platform, plus it can be a colour of your significant other's choosing to match the decor. And, it is much easier than building a frame. Just be careful not to put the contact adhesive onto polystyrene if you use it as your middle lossy layer.
Of course, these are just ideas floating in my head at this point....I haven't built and tried them yet.
Cheers,
Darren.
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Follow Ups
- Re: Help with DIY Symposium platforms - DSK 16:48:30 03/05/03 (1)
- A bit of confusion - David Aiken 23:09:16 03/05/03 (0)
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