I listened to a movie today at quite a nice volume because the kids were not at home. But now I hear a buzzing sound coming out of my tweeters. They are vifa tweeters and I am wondering what's going on. the center and surrounds are not making any sound. The LSI15's are bi-amped. Thoughts?

I think that the first thing I'd try is to "un-biamp" the speakers, and run them on the other amp since apparently the rest of the drivers aren't buzzing. That, or swap the amps and run the tweeters only on the second amp. If the buzzing goes away using the other amp I'd look for a ground fault with the tweeter amp.. If the buzzing doesn't go away, it's most likely the tweeters themselves are possibly "blown", or maybe even some kind of mechanical problem, i.e. a grill or mount buzzing.. How low or high a frequency (relatively speaking!) is the noise?
Best of luck!

I made a mistake. the center is humming in the tweeter too and all the fronts run off of the 7500.

I have the same problem except all my speakers have a slight hum to them and its been that way since day one I just assumed it had something to do with my wire management. Apparently it hasn't bothered me that much because I still haven't taken the time to narrow it down, havn't had the time. When I was just running a Denon receiver to the speakers I never had any noise in my speakers. When I ordered the 990/7700 combo I even made sure to purchase balanced cables so I didn't have any noise and low and behold, I do. The hum is way more noticable when using analog interconnects. I read somewhere on this forum that there was a slight chance the 990 could have a bad chip in it which was really rare but I just don't want to go any length of time without my 990. Maybe this weekend I'll be able to narrow down the problem. Oh yeah, I'm also using dedicated 20 amp receptables.

Guys: I'd definitely start looking for a ground fault in your system & cabling. Google "ground fault" and you'll come up with all sorts of info about causes and fixes.
My system recently had the problem when I hooked in a DTV HD box- The coax feed from the dish is apparently a fairly common source for that type of problem- Check all of your (metallic-) connections, make sure that any 2-prong power plugs all have the phase correct (old gear with the plugs that go in the wall either way have a stripe and/or raised ridge molded on the "ground/neutral" side- they all need to be on the left side of the outlet). While you're at it check the outlets tehmselves to be certain that they're wire correctly. Good luck!

well the common theme between grimster and knownalien is they are both running the 990, and one of the Outlaw Audio amps..

maybe the amp needs a better grounding? Maybe it needs it's own wall plug in? Or a cheater plug.

I have the same 990, but not any Outlaw Audio amps.. and no buzz. I just throwing this out as a similarity between those two people, with very similar problems.

do either of you have differnt amps? DOesn't matter if it's a 2 channel or not. try bypassing the Outlaw Audio amp and see what the results are.

Yeah, but there are too many other 990/Outlaw amp pairings around without a hum to make an interaction the most likely scenario (although it can't be ruled out without finding some other source of the hum that is the real culprit).

the hum is one in which you have to really get up to hear it with your ear right in front of the driver. I should switch and have the 2200's hoocked up to see if there is a hum still.

A hum that low can easily be picked up by cables too close to power cords - that appeared to be the source of it in my system when I had a similar problem a couple years back, and a little judicious cable management resolved it. It's one possibility, at least...

and the amp is just making it louder.. because that's what amps do.. amplify. but worth checking out all possibilities.