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Author Topic: How can I prevent recordings with vocals in one channel and band in the other?  (Read 5575 times)

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Offline jj69

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Seems like the RX Phase tool samples a section to determine the phase relationship between channels across several frequency bands, then seeks to retain that phase relationship if it shifts in other sections.  If that is the mechanism, you'll need find a good "centered" section to sample for it to apply that relationship elsewhere.  It is possible that it could prove helpful in reducing wind-phasing problems as well as knocked-ajar microphone arrangements and unintended head rotation effects with head-worn rigs. 

If this is what it's supposed to do, then it doesn't work.  There is a nicely centered section on my recording.  When I sample that and apply it to the full waveform, the result sounds no different to my ears! 

It seems few people fully understand what these tools do.  What is this "JEM" group that Scooter123 got his ideas from.  Perhaps they have more detailed information about how to use RX? 


Offline Gutbucket

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In that case there may be, and likely are other reasons that the vocals sound un-centered other than a change in of the phase relationship between channels across different sections.  That tool probably targets rather subtle phase changes.  More of a polish thing.  I've not used it myself.

[edit- JEMS is a group of tapers famous in these circles for making quality recordings of big name acts in 70's and 80's under difficult conditions.  They have recently been remastering and re-releasing those cassette based recordings using modern digital tools such as these.  Some of the techniques they use for improving cassette based recordings may or may not apply to modern digital recordings.  Whatever they do to improve the stealth recording related issues is more likely to be applicable though]
« Last Edit: November 03, 2021, 09:39:59 AM by Gutbucket »
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Offline EmRR

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From the RX manual:  The Phase module balances asymmetric waveforms by rotating signal phase. Rotating the phase of a signal changes its peak values but doesn’t change its loudness, and otherwise has no audible effect on the signal.

This can be to make it such that one can maximize level through normalization, without limiting.   It does not have a mode to adjust one signal relative to another that I can see.  Use of it on a bunch of mono tracks that are related could be a disaster. 
« Last Edit: November 02, 2021, 03:03:49 PM by EmRR »
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Offline jj69

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From the RX manual:  The Phase module balances asymmetric waveforms by rotating signal phase. Rotating the phase of a signal changes its peak values but doesn’t change its loudness, and otherwise has no audible effect on the signal.

This can be to make it such that one can maximize level through normalization, without limiting.   It does not have a mode to adjust one signal relative to another that I can see.  Use of it on a bunch of mono tracks that are related could be a disaster.

Yes, my understanding is that this feature is essentially just a phase rotator, designed to balance uneven wave forms. 

Offline EmRR

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From the RX manual:  The Phase module balances asymmetric waveforms by rotating signal phase. Rotating the phase of a signal changes its peak values but doesn’t change its loudness, and otherwise has no audible effect on the signal.

This can be to make it such that one can maximize level through normalization, without limiting.   It does not have a mode to adjust one signal relative to another that I can see.  Use of it on a bunch of mono tracks that are related could be a disaster.

Yes, my understanding is that this feature is essentially just a phase rotator, designed to balance uneven wave forms.


It does tend to sound different too, despite what they say.  Most obvious with voices or horns, which are naturally asymmetric.  It's more of a broadcast trick, if you need maximum coverage within licensed peak limits. 
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Offline rocksuitcase

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JEMS (not JEM)   or, in the old days GEMS.     yup, I'm being THAT guy.... ;D

Search that name on here. They post their work frequently.
« Last Edit: November 03, 2021, 06:55:41 AM by rocksuitcase »
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Offline Scooter123

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It works to correct head movement.  Try it.  Do 30 seconds straight ahead, then 30 seconds moving your head left and right from the sound source.  You can hear the issue first hand.  Then use Phase in RX7 and it will correct that. 

Again, I don't have the technical knowledge of Mr. Bucket or others here, but I know it works.  Check it out and you'll see. 
Regards,
Scooter123

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Offline nulldogmas

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It works to correct head movement.  Try it.  Do 30 seconds straight ahead, then 30 seconds moving your head left and right from the sound source.  You can hear the issue first hand.  Then use Phase in RX7 and it will correct that. 

Again, I don't have the technical knowledge of Mr. Bucket or others here, but I know it works.  Check it out and you'll see.

I just tried it with a couple of recordings where I had turned my body (shoulder-mounted mics) to the side briefly, and it accomplished nothing on those. Which isn't to say it never works, just YMMV.

Offline hoserama

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DeClick routines generally target brief impulses that are not common to both channels.  In other words, those that tend to be found only, or mostly in one channel but not the other.

Seems like the RX Phase tool samples a section to determine the phase relationship between channels across several frequency bands, then seeks to retain that phase relationship if it shifts in other sections.  If that is the mechanism, you'll need find a good "centered" section to sample for it to apply that relationship elsewhere.  It is possible that it could prove helpful in reducing wind-phasing problems as well as knocked-ajar microphone arrangements and unintended head rotation effects with head-worn rigs. 

By contrast RePhase manipulates the overall baseline phase relationship between channels, rather than actively modifying other portions of the file to match a specific target region.

Funny, I've never noticed any preference on spatial balance for RX's declicker. I've seen it zap claps that are dead center and others that are hard panned, no issues.

I use the same method as Scooter123, and find that almost every audience recording needs a little stereo adjustment. The phase/azimuth adjustor allows to account for the couple of samples that the left and right are off, usually due to just slightly less than perfect alignment with PA and/or position in a hat. I do it manually though, and don't use the automatic feature.
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Offline Gutbucket

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^ Good to know.  I've not used the RX Declicker specifically, that's just how some of them have worked in the past. I would not expect it to have any effect on spatial balance, other than reducing an impulse (such as a click or clap) heard in one side more than the other.
« Last Edit: June 06, 2022, 02:54:27 PM by Gutbucket »
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline moondust.and.solitude

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I've been using the RX de-clicker for some time, and it works fabulous. I am very curious about the phase application though. Is this something you let run for the entire wav file or do you only use it in sections that the unbalance occurs?
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Offline Scooter123

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I am mistaken.  It is not phase, it is Azimuth, and RX7 detects moderate to severe situations where the sound arrives at one recording source sooner than the other.  Common audience example would be mikes spaced far apart.  Typically mikes in a hat will have between 3-5 sample difference if you zero in using a DAW, although last week I saw one that was 18 samples, enough to cause a wonky phasing or echo sound. 

i counted the sample difference at a bunch of locations (all slightly different) and settled on 12 samples then set RX7 to move one of the channels of the stereo file.  You can also split the stereo file and manually move it yourself, or use RX7 to "learn" the difference and see what you get.  RX7 said 9 samples, and so I went with that. 
Regards,
Scooter123

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Offline Gutbucket

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Just to clarify.  From the above it seems the RX7 Azimuth tool fine tunes the timing relationship between the two channels by shifting one channel with respect to the other by some number of samples. With the number of samples of the shift being determined either by direct input from the user or via its "learn" analysis function.

In that case, it is essentially moving one channel forward or backwards in time with respect to the other, by small amounts.

Think of the correction not as changing the spacing between two microphones (it can't change that), but rather more like moving one microphone slightly closer or further away from the source in comparison to the other.  In that way its more like adjusting the rotation of a pair of spaced omnis slightly.  But not exactly as it is actually analogous to moving the microphone closer or farther from all sources of sound around it, not just those arriving from the front.


More detail-

Coincident stereo microphone configurations are intended to produce no significant timing difference between the two channels.  The Azimuth tool applied to them can correct (eliminate) a timing difference between channels that shouldn't be there.. or impose one if that were desired for whatever reason.

Spaced configurations (both near-spaced and wide-spaced) will produce timing differences between channels that vary depending on the location of the sound source.  Sound sources on the medial plane (those sounds arriving perpendicular to the imaginary line between the microphones, or in other words, those arriving from directly in-front, above, behind, or below) are intended to produce no significant timing difference between channels, the same as a coincident arrangement.  However, sounds arriving from off-center will produce timing differences that increase proportionately depending on how far off center they are.  The largest timing difference will occur for sounds arriving from 90-degrees directly to the left and/or right. Sources less far over to one side or the other will produce less timing difference. This basic relationship between angle of arrival and timing does not change regardless of how far apart a spaced pair of microphones are spaced.  What does change with spacing is the overall range of the timing difference.   

Good to be aware of this when manually identifying timing offset between channels.  Since the arrival angle in the stereo panorama determines the offset, try to use the impulse of a sound you know is supposed to be centered with respect to the array.

Azimuth adjustment won't change that basic relationship, but rather shifts the overall timing between the two channels.  The Azimuth tool can correct (eliminate) a timing difference between channels that shouldn't be there for sounds arriving perpendicular to the spaced array.. or can serve to intentionally shift the angle at which sounds arrive in unison away from perpendicular to some angle to the left or right of directly ahead (above, behind or below).

musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

 

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