centering the human voice

You might post a photo of your setup. IME if one speaker has corner loading (a sidewall and frt wall) and the other side does not (only a frt wall) you will never achieve a consistent center balance.
A controlled directivity monitor versus your full range wide dispersion speaker would be a better match to your surroundings.

Try placing a mirror on the wall at the same hight as the tweeters. Sit in your listening position and have a friend move the mirror along the wall until you can see the tweeter from your seat. Mark the spot and do the other wall. These are the first order reflections. Place something at that spot to absorb the reflections-like a tapistry or some other acoustic treatment. This will go along way to cleaning up reflections and will improve presence, soundstage and frequency tone. For even better results, continue to move the mirror along the wall until you see the other tweeter-this is the second relection. Treat it the same way. Good luck.

thanks a lot
i guess i need an audiophile to place the speakers for me
despite i know the basics
will keep on trying

Actually, Thromgard gave very good advice. Most any audiophile or enthusiast is likely to suggest the same thing. It's cheap, pretty easy and gives fairly predictable results.

Keep trying and posting results. A lot of us can learn from your experience.

-P

Try taking the recording to a stereo store and listen to thier system to see if the voice is centered to begin with.
As said earlier in this thread not all recordings have the voice centered. At home try this, measure the distance for you to the speakers and make that the same distance between the two speakers. Then try moving the speaker that the voice seems to be favoring further away till you get it to be center. Also reverse the output to see if there is a problem with your amp or speaker, is one speaker loader than the other. This will cause the image to be more to the opposite side. Make sure all the drivers in your speaker are working the same.