Here is a cheap and easy alternative to coins and expensive machined disks.
1.Go to Home Depot or Lowes and go to the Kitchen Design section and grab a bunch of marble or Corian sample disks. They are normally about 1.5-2" square. You can even color-coordinate them to your liking.
2. Now, when you get them home, take a ruler and draw an X on them to locate the center.
3. Take a center punch and center-punch the X.
4. Then take a 3/8" or so drill bit and just "kiss" the mark ONLY JUST DEEP ENOUGH to create a divot such that the point of a cone will catch the divot. DO NOT DRILL A HOLE!
5. You can get even more fancy and get some self-stick felt and place it on the bottom.
Now you have an excellent de-coupling device that even allows you to EASILY move your speakers on hardwood floors with no fear! I did this with my speakers that weigh 240 lbs!!! and they work perfectly.
