Magnitude of loudspeaker-room interaction
 

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.

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.

--
John Phillips

Magnitude of loudspeaker-room interaction
 

With my set up it turned out to be my ears :-(


"John Phillips" wrote in message
...
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.

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.

--
John Phillips

Magnitude of loudspeaker-room interaction
 

On 13 Dec 2004 20:53:46 GMT, John Phillips
wrote:

Is a 2.7 dB left-right stereo imbalance reasonable for a loudspeaker-room
interaction in a nearly symmetrical room?

At what frequencies? All?

Kal

Magnitude of loudspeaker-room interaction
 

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.

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

What are you using as a source, etc?

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

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 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.

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.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Magnitude of loudspeaker-room interaction
 

In message , John Phillips
writes
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.

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.


Is this at spot frequencies, or were you using a 1/24th octave RTA with
pink noise?
--
Chris Morriss

Magnitude of loudspeaker-room interaction
 

In article , Kalman Rubinson wrote:
On 13 Dec 2004 20:53:46 GMT, John Phillips
wrote:

Is a 2.7 dB left-right stereo imbalance reasonable for a loudspeaker-room
interaction in a nearly symmetrical room?

At what frequencies? All?

Well it's 2.7 dB to give a properly central stereo image as I hear it,
over a range of material with a good central image to hear. Also I did
check this with a 250 Hz tone (nearly middle C) written in mono to a CD.

--
John Phillips

Magnitude of loudspeaker-room interaction
 

In article , Chris Morriss wrote:
In message , John Phillips
writes
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.

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.

Is this at spot frequencies, or were you using a 1/24th octave RTA with
pink noise?

No. It was much simpler. I did check the balance at 250 Hz but it
is mainly just set by ear to centralize the stereo image between the
speakers. Without the 2.7 dB attenuation in the left channel (0 dB in
the right) the stereo image is crowded towards the left speaker.

For clarity I run the variable output of my CD player into a power
amplifier through a pair of pi-topology fixed resitive attenuators (Z =
~5k ohms) whose voltage gain (as above) is computed from the resistor
values.

--
John Phillips

Magnitude of loudspeaker-room interaction
 

In article , Garf wrote:
With my set up it turned out to be my ears :-(

Could be with me too. I'm 47 now and the limit to my frequency range is
already down to about 14.2 kHz. There may be other deteriorations too,
I suppose.

However I understand that lateral imbalance in hearing is measured as
a difference in hearing threshold and a difference of 2.7 dB would be
considered as unimportant. More than 10 dB (as I read it from the web,
anyway) is considered significant.

I could not find any material on hearing imbalance at other than hearing
threshold levels which might contribute to my needing to use a stereo
balance control.

--
John Phillips

Magnitude of loudspeaker-room interaction
 

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

Magnitude of loudspeaker-room interaction
 

In article , John Phillips
wrote:
In article , Jim Lesurf wrote:


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

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

Ok. That is usually a 'good sign' so far as room and speakers are
concerned.

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

Balance of the stereo imaging is one of those things to which I seem to be
sensitive. I used to use a 'fine' balance control I'd set up and found that
changes of the order of just a few tenths of a dB made a noticable
difference. And as you indicate, many recordings vary more than this.

FWIW I sometimes find that deliberately using 'cross bleed' resistors to
bring the stereo seperation down to about 20dB actually gives a *better*
image. This gives a better spread for many sources, and slightly reduces
the sensitivity to imbalance from one CD, etc, to another.

- 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.

OK. This isn't my experience as I find even small movements tend to change
the stereo image quite a lot. But this is a general comment, not one on the
average imbalance, and I'm using ESLs which have different diectionality,
etc, to many speakers. Not sure if your report is 'good' or 'bad' news, but
it implies that you are not getting an effect due to unfortunate speaker
placement, etc.

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?

Not sure. Depends on circumstances. IIUC below about 800 Hz we tend to use
phase/time differences, and above that amplitude differences and the
interference effects of the ear lobes, etc. But I suspect the results vary
from one person to another, and one sort of music to another!

Maybe I should burn some innovative combination test tones to CD to see
if this is what's happening.

If you wish to check as a function of frequency, then some 1/3rd octave or
narrower 'mono noise' bands might be useful.

FWIW The 'USHER' disc Musaeus MZCD-T-200 can be useful for stereo
imaging tests as it has sets of tests where the same sound is played with
varied time and amplitude offsets. This is nominally to synthesise
different mic techniques, but it also serves to check the perceived effect
of time and amplitude variation for your hearing in your room and using
your system.

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.

Provided the 'swap' tests showed this stayed firmly in the same 'direction'
so far as perception was concerned I assume your equipment is fine. If the
image is reasonably narrow and well defined, then it is probably OK just to
resign yourself to using the offset and getting results that then sound
fine! About all it then implies is that one speaker might be being driven a
bit harder than the other.

Cheers,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html