Different sound between two channels


I have noticed recently that the sound of my left speaker is slightly different than my right speaker. The right channel appears to be brighter sounding than the left channel with the right channel sounding slightly richer sounding. I've tried reversing my speaker cables at the back of my Pass X250 and the problem kind of switches channels. I'm not sure if the problem is with my Hales T5's or the Pass X250. I think it may be a bit of both. I replaced the voice coils on both the tweeters of my Hales and the sound in general improved but the issue of the right channel being slightly brighter remains. The difference is noticable with the entire speaker as when I play just one channel or the other I notice this characteristic sound with the enire speaker. If my preamp is muted I will get a bit of residual noise from the amp in my right speaker(which is the brighter sounding speaker) and I imagine this residual noise is constant and may be causing the varient sound between the speakers. If anyone has any possible explanation or similar experience your feedback would be appreciated. I should mention that I spoke to Pass and they said it was normal for the X250 to be slightly different between it's two channels and that some residual noise in one of the channels is normal. I should also mention that what I'm experiencing is only noticable when listening right up to each speaker and is not noticable from my listening position.
128x128mitchb
A slightly different (or even more than slightly different) sound from each speaker is normal, in the sense that each speaker's immediate acoustic environment is distinctly unique, despite all the speakers being set up in the same room, due to their different positions within that room, and the fact that almost all rooms and furnishings are asymmetrically laid out to a greater or lesser degree.

But a different sound from each channel of a stereo amp being regarded as 'normal'? Shouldn't be. If the amp is working properly, each channel should sound indistinguishable from the other. To test if your electronics or speakers are actually playing are part in this, or whether it's just what I described above, you should also try swapping the speakers side for side and listen for what, if anything, sounds different.

If the only difference attributable to the electronics really boils down to the noise floor, and you can't hear this from the listening position, then don't worry about it. And remember, when you do any of the listening tests, make sure you're auditioning a monophonic program signal (and if you haven't been, all bets are off you my friend :-)
Thanks Zaikeman,
My room is symmetrical in that it is a dedicated audio/video room and it is 13' by 17' with only a couch in it. I do test with mono recordings and use the mono function of my Pass X1 otherwise. There may be anomolies when using the mono function of my pre as it doesn't send equal signal to both speakers but only blends the high frequencies. It's my suspicion that the differences I am hearing are due to the noise in the right channel which is even there if the preamp is off and is probably added noise to that channel when music is playing regardless of sound volume level. The differences I hear between channels varies with the music I may be listening to. It isn't noticable at the listening position but it bothers me none the less.
To obtain a true full-spectrum mono (summed) signal from stereo disks, you could also insert mated 2-female-to-1-male and 1-female-to-2-male Y-connectors in the line between source and preamp, or between preamp and amp. I still don't like the Pass explanation of different-sounding amp channels as being 'normal'.