[Fleaman]

He's not gonna have a ground loop with nothing connected but AC. It's impossible.

Put your finger on the woofer, can you feel it vibrating? This will tell you if the hum is coming through the speaker or it's the transformer in the amp humming. If from the speaker, try playing with the amp gain....try turning the amp gain down and turning your output gain up (from what ever you are feeding them from), or vice-versa. If this doesn't help, I would think you have something wrong with your monitors or you have dirty AC that the dyna's can't clean up as well as the Events, etc.

If it's the actual amps humming (transformer hum...the back amp plate might vibrate a little too), then again I can only think of either returning/checking out another pair of the same monitors (maybe go to GC or some other showroom), or trying a AC power conditioner of some sort to clean up your AC (again, not saying that's the issue here). You could also take 'em to another house, studio, etc. to see if they hum there (maybe cleaner AC). Pluging them into another outlet in the same building will probably still give you the same AC.