In article , Jim Lesurf wrote:
In article , John Phillips
wrote:
Is a 2.7 dB left-right stereo imbalance reasonable for a
loudspeaker-room interaction in a nearly symmetrical room?

My last system needed no tweaking of the left-right balance control to
get a central image. However my current system needs a 2.7 dB shift in
the balance control. I have checked the source balance and swapped all
components (including leads) and the imbalance remains in either the
room or my ears.

if you've swapped everything in turn, inc the speakers, it does sound like
the room.

Yes - I made notes as I did the swapping. I'll go back and review them to
be sure, but I think it was clearly from the room or my ears (in spite of
the effect not having been obvious on the previous system in that room).

Are you able to get a 'mono' sound with a narrow central image?

Yes. Certainly narrower than on the previous kit in that room.

What are you using as a source, etc?

Varies from CDs I have burned with mono test tones to commercial CDs
with solo instruments and singers (which I find are not all precisely
centred identically in the sounstage anyway - but the 2.7 dB gives a
good overall result).

How much effect does it have to move the speakers or angle them a little?

I have tried that and there's almost no difference in the balance.

I have tried several toe-in angles from zero to having the driver axis
cross just in front of the listening chair. I have kept the speakers
about 0.9 metres from the backwall and adjusted the position relative
to the sidewalls from 0.3 to 0.6 metres. Very little difference.

My experience is that unless you have fairly directional speakers the
actual frequency reponses from the two channels can be distinctly
different, and that this has more effect than the overall difference. The
snag being that you end up having to offset the balance to adjust this if
you can't make suitable alterations to the room or speaker arrangement.

I'll go back and see if I can investigate this a little (although I am
content with the current result and therefore not highly driven to do
too much more experimenting). It's higher frequencies that contribute
most to directionality I assume? Maybe I should burn some innovative
combination test tones to CD to see if this is what's happening.

I assume this imbalance is a loudspeaker-room interaction. The room is
not perfectly symmetrical but not far out. An intruding chinmey breast
is the main asymmetry, apart from furniture.

Approaching 3dB seems a lot in my experience, particularly if the room is
near symmetric. However these things do vary a lot.

That's what I suspected and that's why I am thinking about the effect
and seeking comment. Now that it's all adjusted for balance there seems
to be no problem - the stereo soundstage is all there; it's much wider
and more precise than with the old system.

FWIW In my 'hi fi room' the imbalance with ESL63's was between 1dB and
0.5dB somewhere. In my living room I've got it close to spot-on. How
typical this is, I don't know.

--
John Phillips