Hello everyone, my name is paulo i'm from portugal i'm a sound engineer, right now i'm taking a master's in production and sound technologies at the lusophone university in lisbon.
And I am doing research on a subject related to phase and my questions and doubts are as follows:
1- Is there a way to correct a phase problem only in a given frequency range without changing the other frequencies that are in phase?
2- Is there a plugin on the market that makes the phase inversion only and exclusively in a certain frequency or in a certain frequency group and that allows us to have the possibility to put in the degree we understand (for example I want to invert only the frequency of 250hz because it is out of phase or a range of frequencies for example from 250hz to 400hz and then I control the position of the degree in which they will be placed in phase for example I want that frequency or that range of frequencies is all close to 90 degrees or closer to 30 degrees, and all this without changing or compromising the rest of the frequencies that are in phase?
Thank you !

 

Yep, no problem, for instance
https://www.maat.digital/2bcmulticorr/
https://www.waves.com/plugins/inphase#tab-in-depth (I think)
http://www.aay-audio.com/index_products_aMS-ToolsPRO.html

Ozone should be capable of this too.

On principle every multiband stereo widener can do this because they mostly also offer a narrowing option.

 

Last edited: May 26, 2020

I just happened to know a plugin that can manage phase cancellation issue. Not sure if it will be answering the 2nd question but you can take a look, just in case if it has something be related with your research. I haven't try it myself but had it on my "to-get" wishlist in case I'll be needing the plugin.. here's the link to it..

p/s: keep it secret.. shh
-futurewine
https://www.soundradix.com/products/pi/

ppl don't peek my link. it's secret!

don't click. i'm watchin

 

Also remember that negative correlations doesn't always mean that there are real phase issues. For instance a lot of professional string libraries are having negative values aswell.

 

Why would that happen unless a certain thing caused it? In which case, wouldn't it make sense to correct that thing?

 

I would reach for the Melda production tools for this task. Think it's called MAutoAlign, but the thing is that Melda plugs all can be configured to run multiband as desired, incl. linear phase crossovers if you need them. That particular plugin actually allowed me draw the phase changes I want freehand, as with an EQ. Besides drawing there is also the possibility of "snapping" the phase of different tracks to each other automatically.

 

I think you should always correct it when it's really far into negative, but I don't think a little bit negative is immediately bad as long it still sounds awesome both in stereo and mono. Based on my own experiences changing negative values while nothing sounds bad anyway can still have a big change in your track that could not be sound great as before.

For instance some sounds can sound great when they are wide imo, but then it could result into negative values. Although, when played together with other sounds and nothing bad happens both in stereo and mono for instance, then I quess I can have it like this. If I change it, because of a meter, then this sound will definitely sound different in the end. I think that could be a shame especially when a sound could sound really great in a track.

One thing that I have learned is that I always should try to listen with my ears and therefore not making decisions on only a meter for instance. I check the mix of course in stereo, but also in mono and I try to hear or to check for weird stuff and I love to hear experiences or feedback from other people aswell.

 

Last edited: May 26, 2020

You can try:

• Nugen monofilter
• Sideminder
  
• or my "Phase reflect" mode in FFT tool . REAPER JSFX or load in ReaJS .

 

What you are looking for is called an Allpass filter.it allows you to change the phase of select group of frequencies a certain amount of degrees depending on the corner frequency.for instance,if you use a 1st order allpass filter you'll have 90degrees offset at your corner frequency which will taper off at the stop band.technically there is no stopband with allpass filters so bear that in mind.you can do localised phase rotation with FIR phase rotators but as with all FIR filters you'll be trading phase response for time domain response.long story short it will ring depending on how much phase rotation is required

More to the point.there is not much point in doing it.early reflections will always correlate weirdly with the input sound because of the distance between the different taps in a room for instance and their colour.solutions like Pi should have never been invented as they are essentially a minimum phase allpass filter with an envelope follower that is triggered by correlation.when you move an allpass filter in realtime and especially at audiorate you will get shifts in pitch as the you are displacing the cycles of the waveform briefly.this is what will happen when you use things like Pi on steady state sounds.its obviously not an issue with drums etc,but the concept of dynamic phase rotation is one of those things that was invented for an issue that never existed.its impossible to get 100% correlation across all sounds and all frequency and FYI if you could saynsay deconstruct mixes into their constituent partials and correlate each one then re-encode them it would sound pretty horrible because now all your frequencies are occuring along the zero axis.ever ran a sound through a 100% wet phaser with a lot of stages?that's pretty much what the result would be

And FYI for anybody about to recommend some kind of aligning plugin.delay is not phase

 

@thejohndoe I've no clue what you disagreed with (or what you wrote in your post and what's your personal problem with me) but I was talking about this

Spoiler: Phase before and after

and this can be done done with every multiband stereo widener/imager - on principle as they mostly also offer a narrowing option, like I already said.
But maybe I understood @Paulo A. wrong?

 

You are talking about phase correlation in relation to stereo.he's talking about phase correlation in relation to different sounds and their relative delays at an individual frequency level.that plugin you recommended is some kind of multiband "MID/SIDE"processor.it will only work on the difference of stereo information.it can't be used like say a minimum phase Allpass filter or an FIR Hilbert Transform can

 

Yep.

I didn't know this.

Yep.

I didn't know (about) this.