I thought I would consult you guys here before going loco. I don't calibrate much as I don't swap out equipment often and don't move my speakers. I'm wondering if channel levels can change for other reasons.

I've been suspecting for a few days now that my fronts were softer and finally just ran the test tones on the 950, leading to the inevitable. Yes they were, big time. After tinkering with the S&V disc and SPL meter I wound up with the following settings.

LF 2
CF-8 ***zoinks
RF 2
RS -13 ***zoinks
RB -15 ***zoinks
LB -15 ***zoinks
LS -11 ***zoinks
SW -6

The master volume setting was -15db.

Fronts are on a Rotel 991. Center and surrounds are on a Rotel 985 mkII.

***zoinks = Why the hell are my surrounds and center so loud compared to my mains? Unfortunately I lost my old settings, but I seem to remember that nothing was much more than +/- 7 or 8db.

Could something have happenend to the 991 that would cause lower output? Could something have happened to the 950 to cause such a variation in settings?

We had some power outages due to weather here last week. As I leave the amps on all the time I'm wondering if the power going on and off could have damaged something.

Any help would be greatly appreciated.

The question it's how does it sound??

Well it sounds fine now that I've re-calibrated, but I'm concerned about is why it was out of whack to begin with.

A few thoughts...

First, how does the efficiency of your main speakers compare to the efficiency of your other channels? Less efficient mains may need to be set to a higher trim to match up with the other channels. If a previous calibration yielded settings of between -8 and +8, it's possible that this time you calibrated to a somewhat different point and simply shifted everything down about 5dB.

I hunted down the manuals for both amps on Rotel's site, and neither appears to have trim controls, so presumably there's no reduced trim on the 991 to account for the difference. What about moving the mains to the 985 and trying to calibrate? If there is some problem in the 991 that is causing it to need a higher level input signal, that might be a way to diagnose it (moving the mains to the 985 would then eliminate the 10-15dB difference between mains and other channels).

Another thought - has the balanced/unbalanced switch on the 991 gotten changed? I'd assume that doing so would render the unbalanced inputs completely useless, but it might cause some other odd behavior that would leave those inputs working but at a much reduced level for some reason.

I will switch amps on the mains and see if that sheds any light, thanks. I checked the balanced switch and that was ok. IL30 mains are 8ohm as are the LM1 surrounds.

They are connected with different wire (14ga in-wall for surrounds and 10ga SK for fronts), but again, that was a pre-existing condition.

I've also noticed that the input settings on the 950 seen to occasionally change. For example, I was just setting up the xbox for the kids and it was set on coax 1 instead of optical 1 as it should. We haven't used it since before the storm last week.

I'll do some more tinkering. Thanks for the feedback Gonk.

What are the efficiency ratings on the IL30's and LM1's?

IL30's are 88 db and the LM's are 91 db.

Allright, I haven't been able to monkey with things until now but here are my findings.

I re-calibrated again with the DVE disc and things seem to have gotten progressively worse. Main reference level was set at -02db on the left main! All other levels needed to drop a bit more (close to -15 on all). Switching line level cable between amp & pre/pro did nothing. Speaker cable switch = nothing.

I put the right main on the other amp (the left speaker cable wouldn't reach) and, go figure, +4db or so on the rat shack meter!

Is there a condition that can slowly degrade a power amp signal? I find it hard to believe a digital signal would slowly degrade over time, ruling out the pre/pro (I think - not being an expert).

I am truly desperate to solve this problem as I am about to pull the trigger on a new set of mains (B&W 604s3) and would like to fed them what they want.....which is probably not a bunk signal

Again, any help is greatly (and desperatley needed).

Hmmm... I went back through this thread rather quickly this morning, and it sounds like the most likely source of the problem is the Rotel 991 amp. The impression that I get is that previously you were able to calibrate all channels with the master volume set at 0dB and have perhaps 7dB of variation between channels (with the mains perhaps being dialed higher than the other channels due to a lower efficiency). It also sounds like moving one of the mains to the other amp (the 985 MkII) largely alleviates the problem. That makes me suspicious of the 991. Have you got a local Rotel dealer who can do some troubleshooting on it? Barring that, can you put the center on the 991 and see what happens to the test tone through it?

Thanks for checking back in Gonk. I've been monkeying around with this most of the day, switching inputs and cables and re-calibrating and such, but see if this last procedure I tried makes sense to you.

RF of DVD multi-channel line out ----> Rotel 985 ------> Center speaker....measure with SPL meter.

RF of DVD multi-channel line out ----> Rotel 991 ------> Center speaker....measurement is
-3db.

This by-passes the 950 and all other variants were the same: Program material (DVE test signal), source, cables, and speaker.

Sounds like the amp to me. Next question is what to do I guess.

If you can get the Rotel serviced locally, I'd start with that - at least determine what needs to be done and if it is worth it. If it can't be fixed, then you may need to investigate replacing it. I'm sure Outlaw would be happy to sell you a pair of M200's.

So the answer to the topic question IS.....ME!

Yessir, apparently the only thing that needs adjustment is my brain, and perhaps my ears. I got the amp back from the shop a bit ago and they confirmed that I basically shouldn't own a calibration disc and will be sending someone out to collect my SPL meter.

A friend of mine has told me that different amps have different gains, regardless of power ratings, and settings can vary from one calibration to another due to minor differences in room conditions and other things.

Regardless I got my new mains (B&W 604's) and all is well. I've resigned myself to the fact that I shouldn't nit-pick, turned up the main settings, and am now enjoying as I should've been. Only problem now is the damn 990 is out and I'm thinking I really *should* get the most out of the speakers (although that new Arcam unit looks enticing too).

Thanks to those who responded.

I just bought a Sherbourn 5/1500A 5 channel amp and though i have only played with it a few days, i notice the same thing. The center and surround channels are much louder than the fronts. I have a Video Essentials test disc, so i guess i need to calibrate it, but i dont understand why this would happen.

Definitely calibrate the system (using either VE or the processor's test tones) - it's a critical step for a surround system. As to why there would be a disparity, one potential reason could be differences in speaker efficiency (your center and surrounds possibly being more efficient than your mains).

HA! It's contaigous (sp?).

1 - I would follow Gonk's suggestion of checking specs on your speaks. Resistance can make a difference.

2 - Definately calibrate with a good disc.

3 - Don't listen to me because I obviously don't know what the hell I'm doing.

you should definately research what your attempting to do, before adjusting settings on your preamp, i never let my kids touch my equipment, because they just like to push buttons and look at the pretty lights, but really have no idea what they're doing.

I thought I'd ressurect this thread based on my recent findings....and Gonk, you had it right from the beginning.

I was pulling all my gear out to reassemble on my flexy rack I just finished and saw the switch you mentioned. Earlier I had mistaken what must be a locking mechanism for the balanced inputs for the switch. Well sure enough the switch was in the balanced position.

Of course putting it back into the unbalanced position set things right. Channel settings are once again where they should be, and everything looks nice (finally) sitting on the flexy. Just don't hate a brother 'cause he's ignorant

(BTW the 950 is ultimately vindicated once again)

So the shop didn't comment on the balanced switch back in August? We won't hate a brother 'cause his local shop didn't catch the problem either.