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Default would this phase correction idea work?

hello everyone,

let's say you 2-miked an instrument and recorded it as a stereo file
into the DAW. then when you listened back, you thought it sounded out
of phase.

would it make sense to simply de-couple the stereo file in a wave
editor and then nudge one of the left or right tracks a few samples to
get it in phase?

  #2   Report Post  
siguy
 
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an easier route would be to usa a program like audition or pro tools or
anything and use a phase canceler/converter/changer/whatever plugin to
adjust the phase and just move the slider a little and listen. i would
personally use the phase analysis tool in audition as it will tell you
to an extreme degree of accuracy wether the tracks are in phase or not.
they may also be 180 degrees out of phase as thworing may have been
mixed up somewhere alon your signal path. try inverting one of the
tracks to see what happens. i would not try to manually change the
phase as your soundcard is probably not good enough to be sample
accurate and differentiate the differance if a sound file is ten
samples delayed or something, did that make sense? whatever. give it a
shot.

  #3   Report Post  
siguy
 
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something i forgot to soay is that if you 'nudge' the file at all you
will be adding delay to the track introducing a possible flanger type
effect, ugly.

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RD Jones
 
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No ! The result will not be mono compatible.
And it will only work if the sound is one single frequency.
There is a difference between electrical phase and
temporal (time, for you earthlings) displacement.
If the 'phase' problem was created by latency then
yes - you correct the difference by slipping one file
to line up with the other. If the problem is one side
electrically "out of phase" then the entire right (or left)
channel needs inverted (polarity) but not slipped in the
time domain.

rd

  #6   Report Post  
Takeshi Yamashita
 
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Assuming that the temporal delay was entirely due to distance from the
speaker in question, why would this not be the exact same thing as
latency?

tak

On 2005-01-11 02:26:52 -0500, "RD Jones" said:

No ! The result will not be mono compatible.
And it will only work if the sound is one single frequency.
There is a difference between electrical phase and
temporal (time, for you earthlings) displacement.
If the 'phase' problem was created by latency then
yes - you correct the difference by slipping one file
to line up with the other. If the problem is one side
electrically "out of phase" then the entire right (or left)
channel needs inverted (polarity) but not slipped in the
time domain.

rd



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RD Jones
 
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Takeshi Yama****a wrote:
Assuming that the temporal delay was entirely due to distance from

the
speaker in question, why would this not be the exact same thing as
latency?

tak


If the 'phase' issue is due to time delay from differing
distance, then the effect is similar to that of latency.
But slipping the 2 back into phase with each other will
create it's own effect.
Are the 2 signals both centered and at the same level ?
Better to lower the level of the secondary (delayed)
signal until the phase effect is reduced, or better yet:
Center or near center the first arriving signal, and hard
or far pan the secondary signal.
Hendrix used this effect and I like his work.

The question is what's causing the phasing sound
latency/time issues or electrical polarity ?
And is it objectionable ?

rd

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Arny Krueger
 
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wrote in message
ups.com
hello everyone,

let's say you 2-miked an instrument and recorded it as a stereo file
into the DAW. then when you listened back, you thought it sounded out
of phase.


would it make sense to simply de-couple the stereo file in a wave
editor and then nudge one of the left or right tracks a few samples to
get it in phase?


No, you'd just invert the phase of either of the channels.


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Well, the problem is if you "just invert the phase of either of the
channels" and then listened back in mono, the channels would cancel
each other out and you would end up with a very thin sound. If you're
listening back to the track in the context of the whole mix, it will
probably sound like it just dissappeared!

If you can re-record it, that's the better alternative. If you can't,
then try any of the suggestions you've gotten here and make sure you go
back and forth between mono and stereo to see how the sound changes.
You should always do a stereo/mono comparison flipping back and forth
when recording any stereo track .

If you are going to re-record it, there's an easy way to make the mics
more in phase with each other - While positioning the mics, flip one
side out of phase, listen in mono, start with no EQ or effects on
either and get a good solid sound with your first mic. Then with the
second mic, find the position where the sound cancels the most or
sounds the thinnest. The closer you are micing, the more pronounced the
effect will be. Then ,flip the out of phase side back into phase and do
your mono/stereo comparison. This also works better if the mics are
closely matched.

This technique also works great when recording bass using a mic and a
direct box. Start with the direct sound and then, starting about an
inch away from the speaker, move the out of phase mic away from the
speaker until the sound almost completely cancels and then flip it back
into phase. This will get you the strongest signal. Since bass is
almost always in mono it can mean the difference between a solid or a
weak bass sound - and of course - a weak bass sound means a weak mix!

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ActiveSoundLarry
 
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Well, the problem is if you "just invert the phase of either of the
channels" and then listened back in mono, the channels would cancel
each other out and you would end up with a very thin sound. If you're
listening back to the track in the context of the whole mix, it will
probably sound like it just dissappeared!

If you can re-record it, that's the better alternative. If you can't,
then try any of the suggestions you've gotten here and make sure you go
back and forth between mono and stereo to see how the sound changes.
You should always do a stereo/mono comparison flipping back and forth
when recording any stereo track .

If you are going to re-record it, there's an easy way to make the mics
more in phase with each other - While positioning the mics, flip one
side out of phase, listen in mono, start with no EQ or effects on
either and get a good solid sound with your first mic. Then with the
second mic, find the position where the sound cancels the most or
sounds the thinnest. The closer you are micing, the more pronounced the
effect will be. Then ,flip the out of phase side back into phase and do
your mono/stereo comparison. This also works better if the mics are
closely matched.

This technique also works great when recording bass using a mic and a
direct box. Start with the direct sound and then, starting about an
inch away from the speaker, move the out of phase mic away from the
speaker until the sound almost completely cancels and then flip it back
into phase. This will get you the strongest signal. Since bass is
almost always in mono it can mean the difference between a solid or a
weak bass sound - and of course - a weak bass sound means a weak mix!



  #11   Report Post  
William Sommerwerck
 
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If it sounds "out of phase," the error is a heck of a lot greater than nudging
one channel a few samples can fix.

Are the mics the same model? Are they the same distance from the instrument? Is
there a possibility of polarity inversion somewhere in the chain?

  #13   Report Post  
ActiveSoundLarry
 
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One more thing you might try that hasn't been suggested yet - Just use
the one side you like best and send it through a stereo plug-in or
reamp it out to an amp and mic it. And of course, as always, do the
mono/stereo comparison to check the integrity of your signal.

  #14   Report Post  
Richard Kuschel
 
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hello everyone,

let's say you 2-miked an instrument and recorded it as a stereo file
into the DAW. then when you listened back, you thought it sounded out
of phase.

would it make sense to simply de-couple the stereo file in a wave
editor and then nudge one of the left or right tracks a few samples to
get it in phase?


Yes, that will work for a PHASE problem.

It will not work on a POLARITY problem.

Phase involves time and polarity does not.

If you have a polarity problem, simply invert one of the files.
Richard H. Kuschel
"I canna change the law of physics."-----Scotty
  #15   Report Post  
Arny Krueger
 
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wrote in message
oups.com
]
Well, the problem is if you "just invert the phase of either of the
channels" and then listened back in mono, the channels would cancel
each other out and you would end up with a very thin sound. If you're
listening back to the track in the context of the whole mix, it will
probably sound like it just dissappeared!


I'm keying off the OP, which said

"let's say you 2-miked an instrument and recorded it as a stereo file
into the DAW. then when you listened back, you thought it sounded out
of phase."

I'm presuming that somehow polarity got flipped during the recording
process.

That's what the post says to me.




  #16   Report Post  
Karl Winkler
 
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A "flanger" effect would be a delay but a varying length of delay, i.e.
an "out of phase" pair of signals that change their phase relationship
over time.

Unfortunately, what arrived at the two microphones is a complex picture
of the instrument, and moving the two mics in a time relationship to
each other will not likely fix the problem. However, subjectively, the
sound may improve, although I doubt it.

It may be the case, as someone else pointed out, that simply changing
the polarity of one of the mics may make the most improvement (if one
of the mics was out of polarity in the first place).

Phase and group delay are not necessarily interchangeable...
Karl Winkler
Lectrosonics, Inc.
http://www.lectrosonics.com

  #18   Report Post  
EganMedia
 
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would it make sense to simply de-couple the stereo file in a wave
editor and then nudge one of the left or right tracks a few samples to
get it in phase?
BRBR



Yes. For that reason, I typically record stereo sources to dual mono tracks.
Once I've slipped the tracks until I'm happy I lock them as stereo.


Joe Egan
EMP
Colchester, VT
www.eganmedia.com
  #22   Report Post  
Mark Plancke
 
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would it make sense to simply de-couple the stereo file in a wave
editor and then nudge one of the left or right tracks a few samples to
get it in phase?


Yes, you can do that. Or alternatively you could try one of the
allpass filters available in a plugin form.

http://www.voxengo.com/pha979/

Mark
"In this business egos can be wonderful, but they also can be a curse."
Michael Wagener
  #23   Report Post  
Mark Plancke
 
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No ! The result will not be mono compatible.

Don't ya just love Usenet. bg

Mark
"In this business egos can be wonderful, but they also can be a curse."
Michael Wagener
  #29   Report Post  
ScotFraser
 
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I don't think so. If you want to de-couple tracks enough to make a
difference, you need to nudge them many milliseconds.

Not at all. A nudge of a millesecond or less can result in a substantial timbre
shift.

Scott Fraser
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Arny Krueger
 
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"ScotFraser" wrote in message

I don't think so. If you want to de-couple tracks enough to make a
difference, you need to nudge them many milliseconds.

Not at all. A nudge of a millesecond or less can result in a
substantial timbre shift.


Sure, massive comb filter effects. Is that the best way to deal with the
issue?




  #31   Report Post  
Peter Larsen
 
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wrote:

let's say you 2-miked an instrument and recorded it as a
stereo file into the DAW. then when you listened back,
you thought it sounded out of phase.


Why should it? - what possible cause is it that you have in mind?

Also: You ask about delay, not about phase. Phase unlinearity is about
different delay time in different frequency ranges, which is why it is
compensated - if relevant, it was relevant for analog tape recording,
but hardly ever done, and it was relevant for example for the Sony PCM
F1, in which context I have heard it cause amazing improvement - with a
circuit called an all pass filter.

would it make sense to simply de-couple the stereo file
in a wave editor and then nudge one of the left or right
tracks a few samples to get it in phase?


Allow me to label that an "advanced stereo modification to be used with
great caution by highly skilled operators". It is possible to slightly
alter the "midline axis" of the sound from a valid stereo mic setup by
doing what you suggest, but that is a very different concept.

I have done it twice: with a chamber music recording of a piano trio
that placed themselves somewhat different from what was assumed in the
mic placement and with a mandolin and guitar ensemble that was
asymmetrically positioned on a bar scene to focus their sound in the
direction of the majority of the audience.

The indication for doing was with both recordings a perceived inbalance
that could not be compensated with a simple level change. This was not
about something that sounded "partially out of phase".

The proper thing to do is generally to position the mic pair correctly,
delaying one channel relative to the other is a potential cause of more
problems than it solves and mono compatibility is certainly a major
worry to consider.


Kind regards

Peter Larsen

--
*******************************************
* My site is at:
http://www.muyiovatki.dk *
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Peter Larsen
 
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Laurence Payne wrote:

If you feel one mic was closer than the other, a simple delay may
help. Look at the waveforms at high magnification and nudge one
until they align.


It is not *that* simple - it would be if it was a recording in a sound
dead room, but it isn't - listening is also required and what is
perceived right may not "look right". Great caution is adviced .....
including listening on several loudspeaker setups.

CubaseFAQ www.laurencepayne.co.uk/CubaseFAQ.htm



Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************
  #34   Report Post  
Ron Capik
 
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siguy wrote:

an easier route would be to usa a program like audition or pro tools or
anything and use a phase canceler/converter/changer/whatever plugin to
adjust the phase and just move the slider a little and listen. i would
personally use the phase analysis tool in audition as it will tell you
to an extreme degree of accuracy wether the tracks are in phase or not.
they may also be 180 degrees out of phase as thworing may have been
mixed up somewhere alon your signal path.
....snip..


Hmmm, this has me wondering: What phase analysis tools are out there
in common use? For that matter, are there any good articles or books
that address phase issues in modern audio work [i.e.: radio, live sound,
mastering etc.] ?
I'd like to learn a bit more on the subject, both theory and applied.

Later...

Ron Capik
--



  #35   Report Post  
RD Jones
 
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Ron Capik wrote:
Hmmm, this has me wondering: What phase
analysis tools are out there in common use?


Soundcraft's small B100 and BVE100 broadcast
mixers have an onboard phase meter.

rd



  #36   Report Post  
Scott Dorsey
 
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RD Jones wrote:
Ron Capik wrote:
Hmmm, this has me wondering: What phase
analysis tools are out there in common use?


Soundcraft's small B100 and BVE100 broadcast
mixers have an onboard phase meter.


Yes, and there are a lot of the outboard meters like the Dorrough and
RTW meters that have basic phase metering. I never found these to be
all that useful, though. They don't really tell you anything that mono
summing doesn't tell you, and they aren't any help for getting a sense
of stereo imaging in bad monitoring situations.

An X-Y display like the Tektronix audio monitor is very useful for getting
a sense of stereo imaging when you can't trust your monitors, and it can be
very handy for broadcast and record-cutting work where the sum and difference
channels are asymmetric. But you very seldom see them any longer.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #38   Report Post  
Ron Capik
 
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Scott Dorsey wrote:

RD Jones wrote:
Ron Capik wrote:
Hmmm, this has me wondering: What phase
analysis tools are out there in common use?


Soundcraft's small B100 and BVE100 broadcast
mixers have an onboard phase meter.


Yes, and there are a lot of the outboard meters like the Dorrough and
RTW meters that have basic phase metering. I never found these to be
all that useful, though. They don't really tell you anything that mono
summing doesn't tell you, and they aren't any help for getting a sense
of stereo imaging in bad monitoring situations.

An X-Y display like the Tektronix audio monitor is very useful for getting
a sense of stereo imaging when you can't trust your monitors, and it can be
very handy for broadcast and record-cutting work where the sum and difference
channels are asymmetric. But you very seldom see them any longer.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."


So in effect you're saying that, despite all this talk about group delay
and such, there aren't any tools in common use that quantify these
effects?

Later...

Ron Capik
--


  #39   Report Post  
Scott Dorsey
 
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Ron Capik wrote:

So in effect you're saying that, despite all this talk about group delay
and such, there aren't any tools in common use that quantify these
effects?


Uhh... wait.

I was talking about devices that indicate relative phase between channels.

Which has nothing to do with group delay (phase distortion), although it
can tell you about polarity errors.

All of which are three different things.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #40   Report Post  
William Sommerwerck
 
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One of the best phase-analysis tools is an oscilloscope -- left channel to
vertical, right to horizontal.

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