jim, thanks for that, i thought it might be to do with phase and polar
patterns.

i guess a wide dispersion pattern flat over frequency, same signal coming
from 2 speakers would mimic similar sound waves to a single actual source
located in the middle. thinking back to o'level physics, i guess you could
get a tray full of water and compare two pulsating bobs (two omnidirectional
speakers) with one pulsating bob in the middle and compare the waves
arriving at an equidistant point (the listener).


Fairly flat response with no significant time/phase anomolies.

Controlled dispersion pattern that is fairly uniform as a function of
frequency. (See KH's article on Polar Patterns in this month's HFN.)

Relative absence of colourations or distortions.

Decent listening room acoustics.

Careful placement of speakers and listening location

Appropriately recorded source material.

"Ian Bell" wrote in message
...
Ewar Woowar wrote:

When I listen to some speakers, the stereo imaging is amazing - you can
pinpoint each member of the band on the stage infront of you, yet other
speakers do not have this property.

From a design point of view, how do you go about achieving superb stereo
imaging?

Thanks for any explanations...


Pete


It has a lot to do with the positions of the HF and LF drivers and your
listening position. These result in errors which can muddy the stereo
sound field. The only real solution is to use dual concentric speakers.

Ian



Another strange point: speakers with two drivers almost always produce a
better and more sharply defined stereo image than those with three drivers.
Try a LS3/5a against a Spendor BC1 and you'll see what I mean.


--
Woody

"Ian Bell" wrote in message
...
Ewar Woowar wrote:

When I listen to some speakers, the stereo imaging is amazing - you can
pinpoint each member of the band on the stage infront of you, yet other
speakers do not have this property.

From a design point of view, how do you go about achieving superb stereo
imaging?

Thanks for any explanations...


Pete


It has a lot to do with the positions of the HF and LF drivers and your
listening position. These result in errors which can muddy the stereo
sound field. The only real solution is to use dual concentric speakers.

Ian



Another strange point: speakers with two drivers almost always produce a
better and more sharply defined stereo image than those with three drivers.
Try a LS3/5a against a Spendor BC1 and you'll see what I mean.


--
Woody

harrogate wrote:


"Ian Bell" wrote in message
...
Ewar Woowar wrote:

When I listen to some speakers, the stereo imaging is amazing - you can
pinpoint each member of the band on the stage infront of you, yet other
speakers do not have this property.

From a design point of view, how do you go about achieving superb
stereo imaging?

Thanks for any explanations...


Pete


It has a lot to do with the positions of the HF and LF drivers and your
listening position. These result in errors which can muddy the stereo
sound field. The only real solution is to use dual concentric speakers.

Ian



Another strange point: speakers with two drivers almost always produce a
better and more sharply defined stereo image than those with three
drivers. Try a LS3/5a against a Spendor BC1 and you'll see what I mean.




I'll stick with my Tannoy Monitor Golds thanks all the same.

Ian

harrogate wrote:


"Ian Bell" wrote in message
...
Ewar Woowar wrote:

When I listen to some speakers, the stereo imaging is amazing - you can
pinpoint each member of the band on the stage infront of you, yet other
speakers do not have this property.

From a design point of view, how do you go about achieving superb
stereo imaging?

Thanks for any explanations...


Pete


It has a lot to do with the positions of the HF and LF drivers and your
listening position. These result in errors which can muddy the stereo
sound field. The only real solution is to use dual concentric speakers.

Ian



Another strange point: speakers with two drivers almost always produce a
better and more sharply defined stereo image than those with three
drivers. Try a LS3/5a against a Spendor BC1 and you'll see what I mean.




I'll stick with my Tannoy Monitor Golds thanks all the same.

Ian

On Wed, 12 Nov 2003 18:40:18 -0000, harrogate wrote:

Another strange point: speakers with two drivers almost always produce a
better and more sharply defined stereo image than those with three drivers.
Try a LS3/5a against a Spendor BC1 and you'll see what I mean.

An exception to that is the ATC SCM300As (which have four drive units),
which produce the most incredible stereo image that I have ever heard:

http://www.google.com/groups?selm=un...news.com&oe =
UTF-8&output=gplain

--
Anthony Edwards

On Wed, 12 Nov 2003 18:40:18 -0000, harrogate wrote:

Another strange point: speakers with two drivers almost always produce a
better and more sharply defined stereo image than those with three drivers.
Try a LS3/5a against a Spendor BC1 and you'll see what I mean.

An exception to that is the ATC SCM300As (which have four drive units),
which produce the most incredible stereo image that I have ever heard:

http://www.google.com/groups?selm=un...news.com&oe =
UTF-8&output=gplain

--
Anthony Edwards

In article , Ewar Woowar
wrote:
jim, thanks for that, i thought it might be to do with phase and polar
patterns.

i guess a wide dispersion pattern flat over frequency, same signal
coming from 2 speakers would mimic similar sound waves to a single
actual source located in the middle. thinking back to o'level physics,
i guess you could get a tray full of water and compare two pulsating
bobs (two omnidirectional speakers) with one pulsating bob in the middle
and compare the waves arriving at an equidistant point (the listener).

Yes, however this does not necessarily mean that 'point sources' that
radiate uniformly in all directions are always ideal. Speakers that
approach having a 'planar' radiation pattern which 'beams' the signals
towards the listener may be better. Depends upon the details.

The problem is that when speakers radiate sounds into the room, some then
reflects from the walls, furniture, etc. If the speaker's polar pattern
varies in a complicated, uncontrolled, way with frequency, the result is a
speaker-imposed frequency-dependent variation in the amount of indirect
sound reaching the listener. This can have the effect of shifting the image
in a complex frequency-dependent manner.

Bit like looking at a photo where the colours are all 'out of alignment'.
:-)

Having speakers whose patterns are relatively frequency independent means
the speakers are not having the above effect as they are distributing the
power in much the same way at all frequencies. There may still be effects
due to the room, etc, having a frequency-dependent behaviour, though. Hence
the problem may be reduced, but not removed.

By having sources that tend to 'beam' at the listener, you get a higher
direct-to-indirect ratio, so can reduce the effect.

The above is argued to be one of the reasons why speakers like the Quad
electrostatics can provide good imaging. However other types can also
deliver good performance provided that they, and the room, etc, all are
doing a decent job. Hence there may be more than one way to deal with this
problem. There are various reasons why 'beaming' is problematic in
practice, so it can have drawbacks that may mean another approach ends up
being preferred.

And in the end, of course, the source material has to provide the signals
that can then be used to create a decent image. If the recording/broadcast
is crap in this respect, then even excellent speakers can't give you a good
image. :-)

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

In article , Ewar Woowar
wrote:
jim, thanks for that, i thought it might be to do with phase and polar
patterns.

i guess a wide dispersion pattern flat over frequency, same signal
coming from 2 speakers would mimic similar sound waves to a single
actual source located in the middle. thinking back to o'level physics,
i guess you could get a tray full of water and compare two pulsating
bobs (two omnidirectional speakers) with one pulsating bob in the middle
and compare the waves arriving at an equidistant point (the listener).

Yes, however this does not necessarily mean that 'point sources' that
radiate uniformly in all directions are always ideal. Speakers that
approach having a 'planar' radiation pattern which 'beams' the signals
towards the listener may be better. Depends upon the details.

The problem is that when speakers radiate sounds into the room, some then
reflects from the walls, furniture, etc. If the speaker's polar pattern
varies in a complicated, uncontrolled, way with frequency, the result is a
speaker-imposed frequency-dependent variation in the amount of indirect
sound reaching the listener. This can have the effect of shifting the image
in a complex frequency-dependent manner.

Bit like looking at a photo where the colours are all 'out of alignment'.
:-)

Having speakers whose patterns are relatively frequency independent means
the speakers are not having the above effect as they are distributing the
power in much the same way at all frequencies. There may still be effects
due to the room, etc, having a frequency-dependent behaviour, though. Hence
the problem may be reduced, but not removed.

By having sources that tend to 'beam' at the listener, you get a higher
direct-to-indirect ratio, so can reduce the effect.

The above is argued to be one of the reasons why speakers like the Quad
electrostatics can provide good imaging. However other types can also
deliver good performance provided that they, and the room, etc, all are
doing a decent job. Hence there may be more than one way to deal with this
problem. There are various reasons why 'beaming' is problematic in
practice, so it can have drawbacks that may mean another approach ends up
being preferred.

And in the end, of course, the source material has to provide the signals
that can then be used to create a decent image. If the recording/broadcast
is crap in this respect, then even excellent speakers can't give you a good
image. :-)

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

Jim Lesurf wrote:

In article , Ian Bell
wrote:


It has a lot to do with the positions of the HF and LF drivers and your
listening position. These result in errors which can muddy the stereo
sound field. The only real solution is to use dual concentric speakers.

Interesting. I'd suspect most people wouldn't immediately think of the
Quad
ESL63's as 'dual concentric'. :-) More like 'multiple quasi-concentric'
or 'phased array', though. They image quite well, though.

In some senses this is not surprising since they have little LF response and
most positional information is in the higher frequencies.

Ian