Sandbox - anybody built one?

gold928 · Posted: Sat Nov 07, 2009 2:48 am Post subject:

Granite is best for HARD rock.

Letitroll98 · Posted: Sat Nov 07, 2009 4:41 am Post subject:

I don't have any experience with granite, but I have experience in vibration control and granite would not be my first choice for plinth or support. Granite is a terrible sink for vibrations, they don't dump in the material, they reflect back in it. It might work okay if you built a constrained damping layer with it, two thin slabs of granite separated by a vibration sink like bituminous fabric, sorbothane sheets, sand, heavy closed cell foam, maybe Styrofoam sheets, some dissimilar material to dump the vibrations into. But I still wouldn't pick granite as the first material anyway, and neither do any designers of vibration control plates you can purchase. Just because it's big and heavy doesn't make it good. Wink

The sand box works well because it acts as a sink to dump vibrations into. Notice the top plate is always decoupled from the box itself, resting solely on the sand. This is how vibration control works, whether room treatment or audio equipment supports. You turn vibration into heat by creating a high impedance interface that covers the bandwidth you want to suppress. A sandbox would function as that, a granite slab would not.
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andyr · Posted: Sat Nov 07, 2009 4:57 am Post subject:

Letitroll98 · Posted: Sat Nov 07, 2009 6:10 am Post subject:

exojam · senior member Joined: 24 Jun 2008 Posts: 163 Location: USA

And who said turntable forums only discuss turntables and stuff. We now have a discussion about differenent types of rock! Who knew.

Just having fun since I have no idea about differences in rocks and their properties Very Happy

James

davidsss · Posted: Sat Nov 07, 2009 11:39 pm Post subject:

I must say that the idea of a granite base always seemed a bit strange to me. The weight would help I reckon but the material just wouldn't absorb the vibrations. When looking at my options, and considering I live in an old house with suspended wooden floors, I was looking for something which would absorb the energy of the vibrations. Thinking back to basic physics I know that energy cannot be destroyed it must go somewhere, in other words it needs to be redirected somehow. As such, the sand idea had the most appeal as there is a logical explanation for dissipating the energy of the vibrations, the energy is converted into heat. In practice it has been very good. I would ideally like a wall shelf, although I would still think of using the sand box (that would mean one hell of a sturdy wall shelf though as the sand box is very heavy).

DS
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My System: Micro Seiki BL51 Turntable, Stax UA7 Tonearm, RCM Sensor Prelude Phono Stage, Blue Angel Mantis Cartridge, Rotel RCD865BX Cd Player, Melody I34R (Astro Black 40) amp and Osborn Epitome Speakers.