Where to put damping sheets?

Be careful not to over do it, to much dampening can have an adverse affect on the sound.

Regards,

what kind of adverse affect can putting too much damping have?

On the matress?

The adverse effect is that the music loses it's dynamics and lifelike sound ( duller or darker ).

Mburnstein that's a dumb answer. You don't want damp sheet on the mattress, they need to go in the dryer!

What results did you experience with the places you applied the sheets, and how did the placement relate to the power supplies?