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RE: Since no one else wants to try to answer the question…

Posted by David Aiken (A) on January 29, 2008 at 23:07:01

In Reply to: RE: Since no one else wants to try to answer the question… posted by Bon on January 29, 2008 at 20:58:30:

I can understand the idea behind the sand, and I have to admit that the idea impressed me 40 years ago. I don't think that it impresses me now to anywhere near the same degree.

What you're going to end up with is a column of sand a bit less in height than the baffle so, assuming you're considering this for a woofer enclosure or a 3 way, we're talking a baffle with a 2'-3' sand column, maybe more. While motion of the sand will initially dissipate some vibrational energy and deaden the baffle, over time the sand is going to bed down and at that point it will stop dissipating energy and start transmitting it.

I would be a lot more inclined these days to simply use something like Dynamat to deaden the baffle. If you don't want to do that and you really want to go the sand route, what I'd be inclined to experiment with is a 3 layer baffle. The inner and outer layers would simply be cut out for the drivers. The inner layer, while being cut out for the drivers, would also have a number of large cutouts distributed over the rest of the baffle. I would glue an outer layer to the inner layer, clamp them and allow the glue to dry. Once the glue was dry I would half fill the 'wells' created by the cutouts unique to the inner layer with sand. Only half or slighty more than half fill them, don't fill them entirely because you want the sand to have room for movement. Then glue the final layer of the baffle on to the other 2 , sealing the sand in what are now enclosed pockets distributed over the baffle.

I think you'll get more dissipation with less sand distributed into smaller volumes with less mass forcing the sand to bed down in each pocket. Also, with space left in each pocket, you can actually loosen the sand again at regular intervals simply by rocking the speaker from side to side a little.

I have no idea how effective this idea would be for a baffle, and I have no idea whether the pockets of enclosed air are going to cause problems, but I think in the end you'll get more vibrational energy dissipated by sand motion this way than you will if the sand space is one large void containing a high column of sand.

Overall, however, I think that simply using a material like Dynamat is likely to be at least as effective and a lot simpler to build.



David Aiken

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