Hopefully this is the correct sub-forum for a post like this!

I've been wanting to add a bit more weight to these already solid stands (Sanus Steel Series SF26) for any possible dampening effects and added peace of mind when the animals get a little rowdy (had a close call a couple weeks ago). I found a small bit of info floating around on multiple forums but no picture tutorial. Fairly simple, took me about a half hour start to finish.

Quikrete play sand from Home Depot - $2.99/bag (50 lbs)

I quickly found out that the sand needed to be sifted because the holes in the stands are very small and the pebbles from the sand would block the holes. A kitchen colander worked just fine:

Sifted sand ready for pouring:

Found this funnel at HD when I bought the sand - the small opening worked great for regulating the sand flow into the 4 holes of the stand posts. I added a little duct tape so I wouldn't have to hold it while I waited for the sand to finish flowing:

Added roughly 15 lbs to each stand, worth the 30 minutes it took me to finish the job. You could use lead shot for more weight, but I didn't feel like spending the ~$40 per bag -- the sand works just fine.

Finished product:

Didn't notice any sound difference, but again, was more for the peace of mind so the speakers don't get knocked over when I'm not home.