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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

Showing 3 responses by marktrav

marktrav OP
24 posts
 
I do hear a bit of difference with the shade down. The image moves ever so slightly to the right, but still left of center.

I ended up moving the speaker TOWARD the window about an inch or so, and into the room about an inch or so, and I now have a centered image and gobs and gobs of depth and layering. Well, I had the depth and layering before, it was just off center. :)

I think eventually I'm going to put some proper wall treatments on the first reflection point of the right speaker and some heavy drapes on the windows and see if I can't put that left speaker back where it was.

In the meantime, I guess I'm ok.

Would it have been better to move both speakers closer to each other to avoid the first reflections? Or was what I did by moving the left speaker further away from center but maintaining distance to the listener (by moving it forward) the best "hack" for now?

I guess whatever works, eh?
marktrav OP
24 posts
 
Thanks for all of the responses so far! As mentioned in my prior post, I moved the left speaker OUT and inch, and using a string (tape measure) moved the left speaker forward until it was equidistant to my ears as the right speaker.

All is well now.

The reason I don't like to use the balance control unless it's absolutely a last resort is that I got it in my head somewhere that it causes a phase shift/imbalance or something to that effect. Perhaps it was a manufacturer's ad that made a big deal out of the fact that the balance control was "out of the circuit" when at the 12 o'clock position.

The speakers are an dipole, active crossover design from Linkwitz Labs that I built myself. The crossover happens before the amps, so each speaker gets a direct amp connection. The dynamics are amazing. Everything is amazing about this speaker, and I'm glad the only issue I've had so far is the center image problem.

I sold a pair of Vienna Acoustics Beethovens powered by a VTL ST-150, so I was a bit worried going down this path, but it wasn't a mistake at all. A friend of mine who owns a pair of Maggies (the smaller ones), says mine sound just as good as his on the upper and mid-range, but my bass is worlds better than his. As the designer says, it creates a magic window to the recording.

My ears are clean and super sensitive, which I wished sometimes they weren't. :) Then I wouldn't have these problems. :)
marktrav OP
24 posts
 
I found the problem and I feel like an idiot. Remember, these are 4-way active x-o speakers completely built from scratch.

I had mis-wired the polarity of 4" driver from the instructions. I'm not sure how I did that, but I let it go for months chalking it up to bad acoustics, less than top quality electronics, etc. I was starting to wonder if there was another 4" driver that could be substituted because it just sounded brittle in the upper midrange. The upper midrange is why you spend so much money in this hobby! I upgraded to an Ayre QB-9, a Parasound JC-3+ and a few other things. I was about to start considering the amps.

After a glass of wine in a listening session, I just decided to swap the speaker connections on the 4" driver (knowing full well I'd wired it perfectly when I built it!!!! - NOT!) and low and behold, what a glorious sound!

I returned the balance control to the middle position and returned the speakers to their former mirror image of each other and now I'm in heaven. (Again!)

It's funny how good these speakers sounded for the past several months even with that mistake.

I get to enjoy that "new equipment" high all over again. :D
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