Just to throw my two cents in...
In addition to altering the number of springs and the position you put them in your Nobsound units, another thing you can try is getting 5/8 heat shrink tubing (non glue inside type) and cut it at the length of the spring then heat. Just enough spring will be exposed at the ends once shrunk to put them in the bases. This will dampen the springs action. Try doing some or all of them.
In addition to altering the number of springs and the position you put them in your Nobsound units, another thing you can try is getting 5/8 heat shrink tubing (non glue inside type) and cut it at the length of the spring then heat. Just enough spring will be exposed at the ends once shrunk to put them in the bases. This will dampen the springs action. Try doing some or all of them.