If you are experiencing a Ground Loop Hum from your ESL woofers:
1. Play the speakers enough to turn them on.
2. While the speakers are still on, disconnect the speaker wires only and see if the hum goes away, and if the speakers go into standby in 10-20 minutes. If so, the issue with the hum is somewhere down stream in the system and needs to be addressed there.
3. If the speakers still hum without the speaker wires connected and either one still does not go into standby, try bypassing any power conditioner they may be plugged into and use extension cords if necessary to plug into the same outlet as the rest of the system.
4. You may need to "lift the ground" on the speakers or on certain components to make the hum go away.
The crew at "Audioholics" have created a helpful guide to chase down these sorts of issues in a system. We recommend following their recommendations:
http://www.audioholics.com/home-theater-connection/ground-loops-eliminating-system-hum-and-buzz