Actually, damping or constraining springs in any manner is a bad idea. People have suggested everything from silk fabric to an oil bath to rubber. The best sound is without any damping. If you’re worried that springs ring when you strike them with a small hammer don’t strike them with a hammer when music is playing. 😬 Plus the springs under load are constrained from ringing, like using your fingers to stop a tuning fork from ringing.
Any issues your component might have with high frequency vibration will be affected by mechanical acoustic waves as well as transformers, CD transport mechanism noise, etc. That’s why I oft say a complete plan of isolation and resonance control is required. But the primary problem is the very low frequencies, not the high frequencies, the ones lower than the lowest frequencies the speakers can produce. Any residual vibration on the top plate of the isolating device can be dealt with easily by careful application of damping. Finally, the spring itself does not isolate vibration, it’s the combination of mass and spring that forms the mechanical low pass filter of the isolator.
