I’ve see various fixtures, stand designs, and high-end loudspeakers that call for sand ballast. Just out of curiousity, how does sand compare to other materials for this?
Generic “sand” has a density of 1442 kg/m^3 loose or 1682 kg/m^3 packed.
(Source: http://www.simetric.co.uk/si_materials.htm)
BTW, (1682-1442)/1442 = 16% increase in mass for a given volume by packing the sand.
MDF density is 680-830 kg/m^3
(Source: http://hypertextbook.com/facts/2000/ShirleyLam.shtml)
Iron (as in cast iron or mild steel) is 7870 kg/m^3. (No source, I just converted it from .284 Lb/in^3, permanently burned into my brain from college.)
The relationship between metric and English density units is
1 kg = 2.2 Lbs
1 m = 39.37 in
1 kg/m^3 = .0000361 Lbs/in^3 = 1/27680 Lbs/in^3
So to convert divide [kg/m^3] by 27680.
As it works out, a volume the size of one sheet of MDF is
Loose sand: 1442/27680 * 49*97*.75 = 186 Lbs
Packed sand: 1682/27680 * 49*97*.75 = 217 Lbs
MDF: 750/27680 * 49*97*.75 = 97 Lbs
Iron: 7870/27860 * 49*97*.75 = 1012 Lbs
(Don’t forget that MDF sheets are an inch bigger than plywood.)
The MDF conversion was just a common sense check for the conversion, yes a full sheet of 3/4 mdf weighs just under 100 Lbs.
So since sand is somewhere around twice as dense as mdf, you can have the same mass by putting in twice as much mdf as sand. I like this because sand is messy and mdf is pretty cheap.
On the other hand sand with just enough room to shift may provide additional damping. I’m not sure about that, I’ll have to think about that one.
