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Left / Right Maddening Problem

Hello all,

I have a conventional 5.1 HT / music system: DVD, CD, Pre-Pro, front amp, 3-channel amp for surround and center and self-powered sub.

For a test CD, I use the Stereophile Test CD 002-2, which provides a dog barking to verify left and right channels, a bark that should come from between the two front speakers and an out-of-phase dog bark.

Both the CD and the DVD (with the center and rear channels turned off) exhibit the same anomaly: the left dog emanates from the right speaker, while the left dog comes from the center. Neither is distorted. The center dog bark is perfectly placed and undistorted. The out of phase dog is indistinctly located and somewhat muffled - which is the expected behavior.

Since the CD and DVD are connected to the pre/pro at separate inputs, I think I can rule out the units themselves as being at fault.

I changed the front amp and got the same result. I changed the pre/pro and got the same result. I changed the connecting cables from the CD and the DVD, which also made no difference.

I deliberately reversed the power and ground on one front speaker, which did not help.

Also, I ran the test setup from the pre/pro to make sure that left and right speakers are correctly connected and identified by location.

Lastly, I played the test CD on a boombox to be sure that it does, in fact, produce the dog barking from the left and right side speakers - which it does.

So, now I am unashamedly stumped and am appealing to you all for help. (My wife would also appreciate a resolution to this issue since my testing is making her nuts.)

Any and all suggestions will be welcomed.

Thanks.

Jon
opteron05
ozzy's avatar
ozzy
7,491 posts
 
The most obvious and always overlooked is that the speaker wires are reversed.
I know, we all say thats impossible , but it is easy to do.
Also, perhaps the wire inside the speakers is reversed.

So, start by double checking the speaker wires, and then try other speakers.
opteron05 OP
16 posts
 
Ozzy,

You are quite correct - you can assume, but it's always better to check. I did switch speakers without finding a change. I next re-did the speaker and amplifier connections. The result of this was encouraging: the left dog now came from somewhat to the right of the left speaker, while the right dog was just where he should have been, centered on the right speaker.

Now, one of the nice things about the on-screen display of the NAD T-163 is that you can easily set the db level for each channel. As an experiment, I increased the level on the left front channel by 3 db and ran the test again. This had only a minimal effect on the dog barks, but the soundstage clearly widened a bit when I tested with the Brandenburg #4.

The next thing I did was to stop eye-balling the centerpoint of the distance between the speakers and actually measure. To my surprise, I found I had been sitting slightly to the right of center. Moving over a few inches made a significant difference.

Given the difficult dimensions of the room, the center seating point is actually at the point of a pronounced Isosceles triangle - acccounting for the exaggerated effect of a slight re-positioning.

Since I can't change the room, I'll do what I can with speaker positioning (toe-in, tilting, etc.) and also see what I can accomplish by experimenting with the processing choices available on the T-163. As I once found with my original components, it may be that filling in with the rear speakers will get me closer to what I'd like to hear from my system.

Many thanks to all from me and also from my wife, who is relieved to know that the barking will be much less frequent.

Jon
tobias
1,534 posts
 
Well done Jon! Thanks for the follow-up.

The next thing I did was to stop eye-balling the centerpoint of the distance between the speakers and actually measure.

That worked for me too. I set up according to Jim Smith's suggestions ( it's a good book--really ) and things were fine. A week afterwards the image had gone screwy, and it took a measuring tape to tell me that I was not actually sitting where I thought I was.

It may seem like barking madness to others, but when it's just right there's no denying the difference.
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