Any Way To Damp Ringing Stands Without Adding Weight???

I have the 4 post Pangea stands.  I used the closed cell foam pipe insulation as referenced above.  Seems to work well, as I don't feel any vibration with music playing.  I decided to try this because I once used similar inserts designed to be inserted in steel golf shafts to cut down on vibration.  Worked there too.

@dill "Do not use kitty litter ever"

Why?

It absorbs moisture and will eventually clump up and harden inside your speaker stand, making it a challenge to empty if need be. A better fill is small pebbles, dried play sand or a mix of the two (both available from Home Depot or Lowes) don’t use sand from the beach. I also recommend Herbie's Gliders under the spikes.

Although not reversible, I know a few DIY stand/rack makers that use expanding spray in foam (available at any hardware store) to dampen hollow tubes.