First post, so bear with me if I goof this up

I'm considering buying a 990/7500 pair with a set of Onix Rocket speakers. The mains are 8ohm. The center is 4ohm. The dipole surrounds are 6ohm. Will this create any kind of strain on the amp? I know that sometimes people are concerned about leaving channels without load or balancing load such as with vertical biamping. So, if I have this mix of 4, 6, and 8 ohm, will it cause reliability problems?

If the answer to that question is no, would I expect to have to adjust channel gains on the prepro to compensate for the differing loads? I know that the lower loads receive significantly more wattage (even though it is more difficult for the amp to drive). Am I to expect the 4ohm center to be putting out a much hotter signal than the 8ohm mains? Most of the other speakers that I looked at such as Paradigms seemed to have consistent impedance all the way around on a 5 or 7 channel setup...so these Onix speakers throw me off a bit.

I guess a final quick question might be (if any are familiar with the onix speakers)...would the 7500 be a good amp to drive Rocket 760s, 200 center, and 300 surrounds? Just curious.

Thanks to anyone that may respond. Take care.
-Andrew

I don't think you will have a problem. I believe that speakers are always changing the ohm that the amp sees anyway depending on what they are playing at the moment. The ohm rating on speakers is more of an average impedence. It's not absolute. Your 8 ohm speakers may dip down below 4 ohms on certain passages. As to whether that will cause any gain problems. I don't know. All of my speakers are 4 ohms and I haven't seen any problems. I would guess that the calibration procedure would take care of most of that.

rmilewsk, is right. The only time your speakers are at 4, 6 or 8ohm is when there just sitting there not playing at all. When in use they will drop and rise in impedance according to what is being played. Most conservative home receivers and seperate amps are stable down to AT LEAST 4ohm. I had an older pair of Paradigm 11SE's rated at 4ohm. Ran those puppies on any and everything imaginable and never had a problem with an amp overheating. I think you will be fine.

Your biggest worry is getting a proper spl balance between all the speakers. And even that's not all too difficult.

You should not have issues driving your speakers with the 7500.

When you get all of your gear, you should setup your system with a sound meter or autocalibration routine. This calibration should properly compensate for the differences in the speakers/ loads.

ditto ratpack!