Getting phantom image perfectly centered


This is driving me nuts! I can't get the image centered unless I turn the balance control on the preamp to the 1:30 position. I've tested the system from source to loudspeakers from an electrical standpoint, so I know each speaker is getting the exact same electrical signal with a test tone and each speaker outputs the same dB with the same test tone.

So, it HAS to be the speaker room interaction, right?

I've read http://www.linkwitzlab.com/listening_room.htm and I THINK I understand everything.

All of the following measurements are in inches:
The room is 189 long by 144 wide. (15.75 feet by 12 feet)

The speakers are precisely 45.5 inches from the back wall.
They are each 26.5 inches from the side walls with a caveat. The left speaker is 27.5 inches from the window sash, which is 1 inch deeper than the wall. It's 30 inches to the top panes of glass and 28 inches from the lower panes of glass. But measured from the actual wall, both speakers are exactly 26.5 inches from the wall.

The speakers are precisely 90.5 inches apart.

The listening position is pretty close to 45.5 inches from the back of the room. The back of the room is open to the rest of the house and the wall on either side of the opening is symmetric with each partial wall being 36 inches.

Listening to a recording were I know the voice is dead center, the voice is actually just to the left of centered, and I mean "just". Would you recommend moving the left loudspeaker towards the center an inch or two?

What kinds of techniques to you use to "dial it in" when you've got a really revealing system and you are past the "math" and it's all more art than strict science?

I think you should be able to see a picture of my listening room here: http://orion.quicksytes.com/download/file.php?id=3096

My apologies if this isn't the right sub-forum to post this question to.
marktrav
Whatever works. Every room is different. Not every setup will have symmetrical acoustics so there is no rule that says your speaker placement must be symmetrical either.

Also all speakers have different dispersion patterns at various frequencies. Its usually a good idea to get a handle on that case by case in order to figure out best placement option faster.

Its always best to avoid early wall reflections for best imaging. The tradeoff is that distance from walls often will lower bass levels. What sounds best always varies case by case. So don't be afraid to experiment and do whatever works. Should not be needed is all is well but having a balance control provides yet another option.
To be clear, you tested the components by switching the places of the left and right speakers and the image still skewed to the same side? Speaker imbalances/difference are apt to be more significant than any electrical component. I also presume you tested the overall electrical balance of your system by switching the speaker leads from the amp going to your speakers?

If it is truly room issue, the easiest fix is to use the balance control--just leave it at the 1:30 position--that is what the control is designed to do. I am amazed how many listeners do without a balance control, I find it essential.

The other way balance can be restored is to move one speaker forward by a small amount (I would work with 1/2 inch increments). The closer a speaker gets, the more the image shifts toward that speaker because of higher volume (less fall off of volume because of distance) and because, of a timing change (your brain will interpret the sound coming first from the nearer speaker as an image shift in that direction). I personally don't like skewing the image position a lot by making such a position change, so again, I prefer to just use the balance control.

It is always productive to try changes in speaker placement and placement of your listening chair. But, when doing this, keep in mind that there are other considerations than getting the image to center correctly. Be sure to get the balance of bass frequencies correct and avoid positions that cause sound to wildly change when you make minute changes in your listening position.

Trying to treat the room to cure this problem will not be easy to do. If there is an imbalance in sound arriving from one direction, a big compensating change to absorb some of that energy to "balance" the room will inevitably create tonal changes because it is nearly impossible to uniformly absorb sound energy across all frequencies. The result of such treatment is unpredictable. But, if the problem has to do with standing waves and other such forms of constructive and destructive interference of waves, some treatment, such as bass traps in the corners could be helpful. I would also also try very modest wall treatments, such as putting tapestries on walls, before going wild with specialized room treatments.

Finally, I note that your speakers are quite far apart for your listening position. Even if you toe them in to face much more directly at your listening position, it would be hard to get a very solid sounding middle. If possible, you should at least try moving the speakers much closer together.

Good luck on your experiments.
The speakers are precisely 45.5 inches from the back wall.
They are each 26.5 inches from the side walls with a caveat. The left speaker is 27.5 inches from the window sash, which is 1 inch deeper than the wall. It's 30 inches to the top panes of glass and 28 inches from the lower panes of glass. But measured from the actual wall, both speakers are exactly 26.5 inches from the wall.

The speakers are precisely 90.5 inches apart.

The listening position is pretty close to 45.5 inches from the back of the room.
Larryi, I don't think his speakers are too far apart.
Looking at the photo of his room it looks like he has the speakers setup along the long dimension i.e. along the 189" dimension.
if the speakers are 45.5" from the wall & the listening position is 45.5" from the other wall, then, he should be 98" from the speaker which is little over 8 feet. The speakers are 90.5" apart which is 7.5 feet. I don't think that his speakers are too wide vs. his seating distance.....
maybe you mis-read one or more of the dimensions in his orig post??
Marktrav, real nice system and setup. If the balance control centers the sound image, then don't worry too much about it. That's what balance controls are for. You could also move your listening position by a small amount to achieve a similar effect.

Since your loudspeakers are designed to work with the room I would caution you about the use of acoustic room treatments on the side walls.