CD/DVD Tweak ?

Is anyone using a heavy weight on top of their CD or DVD player? What's the purpose of this? What's the best material to use? I would think that it would reduce the players internal vibration. What does this tweak do for sound and or video quality?

How does this tweak work with air isolation? Should both methods be used(heavy weight & air) or just one or the other? I'm a little confused. Is this worth trying or is it voodoo?

Thanks,

Rob