A phase question
 

I know this to be true but have often wondered about the science behind it.
In them old analogue days I built a Mullard circuit for an image width
control. Basically it was a device for adding the sound from the opposite
channel to the other from fully in phase, ie Mono, to completely out of
phase, but in the process, you could often find a position where the stereo
was wider or the sound was more spacious. Of course it did reduce the
central image a bit.. However I built such a control into Goldwwave using
the channel mixing adjustments and yes it works the same way.
The question is, why?
Brian

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A phase question
 

Brian Gaff wrote:

-----------------------

I know this to be true but have often wondered about the science behind it.
In them old analogue days I built a Mullard circuit for an image width
control. Basically it was a device for adding the sound from the opposite
channel to the other from fully in phase, ie Mono, to completely out of
phase, but in the process, you could often find a position where the stereo
was wider or the sound was more spacious. Of course it did reduce the
central image a bit.. However I built such a control into Goldwwave using
the channel mixing adjustments and yes it works the same way.
The question is, why?



** Most stereo recordings rely on amplitude differences to create apparent positions for sounds when listening to a stereo pair of speakers. Same amplitude and phase in each channel creates an image in the middle of the pair, for an ideally situated listener. A dB or two difference in amplitude moves the image over to the stronger speaker. A 10dB or more difference moves it all the way.

A "width control" used at max ( ie expand) setting sums a reverse phase version of one channel with the other so cancelling any central image on the recording. Sounds that appear left and right of centre do not have equal amplitude and undergo far less attenuation. Sounds that appear purely in one channel suffer no attenuation.

The reverberation on a stereo recording has little correlation in the two channels so is unaffected by the expand setting of a width control.

The net result is as you described, the central image is diminished while far left and right sounds PLUS any reverberation remain the same.


..... Phil

A phase question
 

In article ,
Brian Gaff wrote:
I know this to be true but have often wondered about the science behind
it. In them old analogue days I built a Mullard circuit for an image
width control. Basically it was a device for adding the sound from the
opposite channel to the other from fully in phase, ie Mono, to
completely out of phase, but in the process, you could often find a
position where the stereo was wider or the sound was more spacious. Of
course it did reduce the central image a bit.. However I built such a
control into Goldwwave using the channel mixing adjustments and yes it
works the same way.
The question is, why?
Brian

To alter width, you normally convert from L&R to M&S. (mono and difference
signal) If you alter the gain of the difference channel only, you alter
the width. Then convert back to L&R.

--
*Eagles may soar, but weasels don't get sucked into jet engines *

Dave Plowman London SW
To e-mail, change noise into sound.

A phase question
 

Dave Plowman (Rabid Nutter) puked:

-----------------------------------


To alter width, you normally convert from L&R to M&S. (mono and difference
signal) If you alter the gain of the difference channel only, you alter
the width. Then convert back to L&R.


** That must be straight out of the Mad Magazine Guide to Hi-Fi.

http://forums.stevehoffman.tv/thread...m-1958.197757/

Totally bonkers.



...... Phil

A phase question
 

Well, I'm familiar with the old Hafler way of trying to add a rear channel
certainly, by only feeding the difference signal to the rear, which nulls
out anything placed in the middle of the sound stage, ie, with completely
in phase signals.
its the opposite of mono.
I was more wondering how the part way phase cancellation makes the
differences it does. Not all recordings really sound right, but playing
around last night with the old Wings over America recordings, you can make
it sound much more 'live' than it did in the first place with apparently no
problems with the centre, better stereo and more subtle ambiance from the
venue.

I think the first post in this series sort of makes sense, but if it were
just that, all stereo recordings would have a better separation, and
ambience,and they don't. I can only suggest that the brain here is making
the difference when it hears something that it recognises as 'right' against
the sort of panned multi track stereo you can hear from some close miked
recordings with artificial reverb added here and there. For example it fails
miserably on those old decca Phase four stereo recordings like Two pianos go
to Hollywood with obviously hard stereo panned pianos at either side.

Brian

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This newsgroup posting comes to you directly from...
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"Phil Allison" wrote in message
...
Dave Plowman (Rabid Nutter) puked:

-----------------------------------


To alter width, you normally convert from L&R to M&S. (mono and
difference
signal) If you alter the gain of the difference channel only, you alter
the width. Then convert back to L&R.


** That must be straight out of the Mad Magazine Guide to Hi-Fi.

http://forums.stevehoffman.tv/thread...m-1958.197757/

Totally bonkers.



..... Phil

A phase question
 

In article ,
Phil Allison wrote:
Dave Plowman (Rabid Nutter) puked:

-----------------------------------


To alter width, you normally convert from L&R to M&S. (mono and
difference signal) If you alter the gain of the difference channel
only, you alter the width. Then convert back to L&R.


** That must be straight out of the Mad Magazine Guide to Hi-Fi.

http://forums.stevehoffman.tv/thread...m-1958.197757/

Totally bonkers.

Talking about basics, pet. Not something you'd understand.

--
*I couldn't repair your brakes, so I made your horn louder *

Dave Plowman London SW
To e-mail, change noise into sound.

A phase question
 

In article ,
Brian Gaff wrote:
I think the first post in this series sort of makes sense, but if it
were just that, all stereo recordings would have a better separation,
and ambience,and they don't.

Saying, as Phil did, that only relative levels between L&R determines
positioning is simplistic nonsense.

It's why stereo created by pan potting mono sources ends up sounding very
false. Might well be what you want, of course.

--
*If at first you don't succeed, redefine success.

Dave Plowman London SW
To e-mail, change noise into sound.

A phase question
 

tiistai 31. lokakuuta 2017 10.45.03 UTC+2 Brian Gaff kirjoitti:

just that, all stereo recordings would have a better separation, and
ambience,and they don't.

In true stereo recordings (XY pair, AB pair, Jecklin disc, Decca tree, etc you are not looking for "separation". The objective is to capture the orchestra's internal balance with the ambience of the hall in question, with each instrument or section focussed correctly in the stereo soundstage.

If you want separation, you record multitrack, and bricklay, one track at a time. That way you get 100% separation, which enables you to later use cross-pan reverb etc etc.

I can only suggest that the brain here is making
the difference when it hears something that it recognises as 'right' against
the sort of panned multi track stereo you can hear from some close miked
recordings with artificial reverb added here and there. For example it fails
miserably on those old decca Phase four stereo recordings like Two pianos go
to Hollywood with obviously hard stereo panned pianos at either side.

In the Ronnie Aldrich two piano recordings on Decca Phase Four, the pianos are two separate overdubbed tracks in mono recorded with a vintage STC 4021 "Ball and Biscuit" moving coil microphone. (Many different mics were tried, but the STC gave the best Phase Four piano sound) One piano track is panned left and the other right in the stereo mix. Each has its own reverb, (EMT 140 to match that of the studio) applied after EQ and compression. The method works well, as intended.

Best regards

Iain

A phase question
 

Dave Plowman (Criminal Nutter) puked:

---------------------------------------




To alter width, you normally convert from L&R to M&S. (mono and
difference signal) If you alter the gain of the difference channel
only, you alter the width. Then convert back to L&R.


** That must be straight out of the Mad Magazine Guide to Hi-Fi.

http://forums.stevehoffman.tv/thread...m-1958.197757/

Totally bonkers.


Talking about basics,


** Talking right out your stupid FAT arse.

And you do not know basics or ANYTHING else.


Die soon, you vile pommy ****.

A phase question
 

Brian Gaff wrote:

-----------------------


I was more wondering how the part way phase cancellation makes the
differences it does.


** Been thoroughly answered.

Shame you do not like it.



Not all recordings really sound right,

** You did notice the word "most" in my post?



I think the first post in this series sort of makes sense, but if it were
just that, all stereo recordings would have a better separation, and
ambience,and they don't.


** Utterly mad assertion.

Recording engineers decide on these issues.



..... Phil