Humming noise from Tweeter?

Ground lift the system.

(Dont use the ground leg on the power wire.)

This problem has done to death (i.e., search the A-gon archives) but...
1. Are you using a dimmer switch on any lamps?
2. Does hum come from both tweeters or only one?
3. If only one hummer, switch the speaker cable and see if hum follows. If yes, then work your way back to preamp and swith cables there and see what happens (we're trying to find the source of the hum).
4. If you have cable T.V. hooked up to your system, disconnect and see if this helps. These are bad,bad,bad...
5. If possible, open your speaker and check all connections (disconnected from your amp, of course).
6. Try to borrow some ferrite rings from your "friendly dealer" and see if RF (radio frequencies) are causing the problem (you run your interconnects and speaker wire through these and they "soak up" RF).
Hope this helps...