I suspect your room is the problem. May I suggest that you reverse the speakers, right to left and left to right and do the same for the rest of your system piece by piece working backwards. If you do not find that the system reverses it's volume imbalance, I think it's safe to assume it's the room or your ears and not the equipment. You might want to have your ears checked( many years ago I thought I needed a new TV, turned out I needed glasses!). If it's the room, you can change speaker placement, try room treatment, try digital room correction or any combination of the above. Good luck.
If you check that the voltage going into the left and right amplifier channels (or monoblocks) is matched within less than 0.1 volt, there is no point in reversing any of the components upstream. If you also have measured the amp outputs to the speakers and find those to be matched, then its either the room (most likely), the speakers (less likely), or just conceivably a problem with one of the speaker cables.
There are many things you can do to diagnose the source:
Regarding the room, if the room is not already well treated acoustically, try taping heavy sheets over all reflective surfaces, which will deaden the sound but leave you with only the direct reflections from the speakers, and check the center imaging as you do this. It's been a source of amazement to me how much effect reflections coming even from walls in adjacent rooms have on image formation. The ceiling and floor are equally important.
Regarding the speakers, you can measure the amplitude response of each speaker at a group of frequencies across the audio band. I would borrow a measurement setup for this (microphone + measurement equipment) rather than doing it by ear.
Also, you can just use the balance control on your preamp, if you have one, to offset the apparant gain difference. This is cheap EQ.
It is not abnormal for one of the drivers in a speaker to "settle in" or alter output and / or frequency response over time. As such, what may have started out as "matched pairs", etc.. of drivers no longer "match". This can result in changes in volume level, imaging, harmonic structure, prat, etc..
Unsound and Flex both offer good ideas. However, I would start off by simply pulling all of your cables ( ONE by ONE ) in the system and simply re-seating them. This is simple and may help solve your problem. This should be done on a somewhat regular basis as "crust" does develop on connections over a relatively short period of time.
If that does not work, i would try swapping speakers from left to right. Obviously, it would help to mark the positioning of both of these prior to shifting them around. If the problem is speaker based, you should hear the channel imbalance with the left side being louder now.
If the right channel remains louder, you either have something wrong upstream in the components or you are experiencing problems with how the room loads up. You would have to do some step by step "detective work" to find out if a component or cable was responsible for this. What you measure under a no load condition ( voltage levels measured at the outputs but with nothing connected to the device ) can be quite different than what takes place under loaded i.e. "connected" conditions. If all of this checks out, you know that the components and speakers are okay and it's time to look at room treatments.
If the problem did shift channels when moving the speakers, you would need to use a test disc with various test tones and an spl meter to see what was going on. Put the system into mono mode and then measure the driver on one speaker at a specific freq and then measure the other. Nearfield measurements taken on axis ( basically directly in front of each driver as close as is reasonably possible ) is the way to go here. Obviously, the placement of the SPL meter should remain as consistent as possible from driver to driver and side to side.
It would not be abnormal to see small variations from side to side due to less than professional testing conditions. However, a very noticeable difference would point to a driver or internal crossover related problem.
Hopefully, this will give you some ideas as to where to go. Let's hope that it is something simple. Sean
I agree wholeheartedly with the above suggestions, especially Sean's when he recommends unplugging and replugging all of the component connections.
Here is my two cents worth from a slightly different angle. Variations in the recording process will often cause the problems you are experiencing. A possible solution is to move your speakers slightly closer together, or your listening position back. The sweet spot will widen somewhat and allow the listener to shift around in the seated positon (as we all do) without shifting the stage.
Whenever I do serious listening in my room I must close the entry door as well as the sliding door to my patio. The veritcal blinds must be positioned slightly opened toward the speakers making them a trap rather than a pure reflective surface.
The purpose of describing what I must do to enjoy serious listening is to make you ask what, if anything, you are doing differently when this phenomenon occurs.
Hope things get sorted out and...
This is a semi-quibble with Sean but nothing serious. If you are doing the XLO measurements with their test disc, then you are using a simple tone directed to the left, then to the right speaker, and measuring the amplifier output voltage as the system plays, i.e. under load. In this situation, if the voltages match (and I have to borrow voltmeters from work to get to the millivolt ranges they are referring to), then you are accounting for all the upstream contributions, so you wouldn't need to go through switching components. Reseating cables periodically is still a good idea (and cleaning terminations, while you're at it).
If you are using balanced interconnects, make sure that the are fully inserted. If one of the hot pins is not making contact you might loose 1/2 of the input signal for one of the channels and throw the system out of balance. I had this happen, turned out to be a bad xlr connector. Good luck, Bob D
I heard nothing from the right side 3 weeks ago and almost panicked.It turned out to be one heck of a sinus infection on that side that also had me going to the dentist because I thought a filling fell out, it hurt so bad. Decongestant and antibiotics later, things are back in order. Also, on the smaller side of things,sometimes I think the couch gets moved off center by the kids or the dogs. Balance control helps here until the couch gets recentered. Sometimes those speaker wires work loose as well and need tightened. Can tubes going bad create the same thing?
First of all, I would like to thanks urs helps, I really appreciate. However, I tried many methods but still failed. Hopes u guys can give me some more adv. on it.
( Still using the XLO test CD )
1st step : I tried to swap the inteconnect from left to right, n right to left, just to be sure no problem from my front sys.It happen the same, the center vocal still tends to go to the right. About 1 foot.
2nd step : I swap the speakers, same works , L to R, R to L, , however it still the same, Center goes to the right, stay at the point 1 foot.
3rd step : I swap the speaker cable, same works, L to R , R to L, n yet it still the same, center vocal goes to the right.
4th step : I move around the speaker, just can't work out. I had tried many movement, but failed.
So My Q is that, if I want to get back the vocal to the center from the right, wht shd I do, I had the identical on both side, as this sound room was special designed to be identical, on both side of the wall, as well as ceiling, floor carpet, from wood wall.. Thanks again from the fans above , n just need more adv.Thanks again!
I had exactly the same problem. It was my room. Try moving speakers forward if possible, and try some sound proofing at the first reflection (doesn't have to be large). My balance is fine now. Good luck!