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What does it mean if an element in a mix is in the "side" AND "mid" channels

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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby armans » Thu Nov 19, 2020 10:53 am

Mike Stranks wrote:Do you know how this track was recorded/mixed? Do you have access to the original guitar track(s).

I've just had a very quick listen to the sample you've provided. I've only used my ears, but I suspect that the guitar part was recorded with one mic and that it has either been put through some sort of 'stereoising' process or it has been duplicated and then delayed by a few milliseconds with each track then panned left/right.

Just my initial impressions having listened to about 30 seconds...

Hi Mike. Thanks for listening but I think the best way to see what I mean is to actually open up the clip (it is only a few bars long) and test the side & mid channels so you can see what I mean.

If the guitar was recorded with one mic and duplicated, or if the the copy was delayed by a few miliseconds as you say then when auditioning the "sides" in any mid side plugin, the guitar signal would be somewhat removed and the uncorrelated signal would be what is left as the sides = L - R but in this case, the guitar is perfectly audible in the "side" so how can this be?
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby Rich Hanson » Thu Nov 19, 2020 10:59 am

armans wrote:similar.

This word here is key - they are only similar and not the same. Your expectations are for signals that are identical. If the L and R are not identical then they will not cancel - if you can hear a difference between L and R then there is a significant Side component.
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby Hugh Robjohns » Thu Nov 19, 2020 11:02 am

armans wrote:... there is a problem. The same guitar part is in both L & R channels.

So if that same guitar part was identical in both the Left and Right channels it would -- by definition -- sound central... And it most definitely doesn't... Ergo, it's not the same guitar part in both channels.

If the side channel is the difference between the two channels and the guitar parts are almost identical on both L & R channels in the chorus then they should effectively cancel each other out when the "side" channel is auditioned but this is NOT what is happening here. When I listen to the "side" channel during the chorus the acoustic guitar is perfectly audible with no cancellation at all.

If there's little or no cancellation when listening to the stereo difference signal then the two tracks are not very similar. That's the only way the maths works! They might be dissimilar in their amplitude, their frequency content, or their phase/timing -- or all three. And it doesn't actually take very much dissimilarity to leave a lot of signal in the Side element.

In your track I'm hearing different guitar parts left and right.
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby Hugh Robjohns » Thu Nov 19, 2020 11:06 am

armans wrote:I tried this and there actually is a difference between a left panned guitar and using the three channel approach mentioned above. The resulting signal actually seems to be panned further than left if that makes sense.

That's because your track levels aren't matched correctly and your panned and inverted polarity LR signals are louder than your centre-panned track. Probably due to the panning-law in your DAW which will attenuate a centre-panned signal by between 3 and 6dB.

It ain't magic. There's reliable science determining all this... but you need to be aware of all the elements in the signal paths...
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby CS70 » Thu Nov 19, 2020 11:26 am

armans wrote:
CS70 wrote:Y

If you take the guitar on three tracks, one panned central, two hard panned L and R, and reverse the polarity of one of these two (like a figure 8 mic does between the two sides of the capsule), you would get that effect: when both M and S are present, the two hard panned guitars on the L and R cancel each other, leaving only the one centered, but if you mute the mid channel, what is in the side are the two hard panned guitars in reverse polarity which, when making the difference, actually sum up.

:clap: this is very interesting, :thumbup:

but why on earth would you do something like this? :o

would you be so kind as to listen to the clip I uploaded and see if you think this is what is happening?

Very wide stereo image with good mono compatibility. You want to alter the copied tracks with a bit of delay and EQ - to mimic the fact that in a real M/S the two mics are different and the side mic captures reflections from the side walls.
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby CS70 » Thu Nov 19, 2020 11:31 am

Hugh Robjohns wrote:Double-tracked guitar parts are usually different enough to be sufficiently incoherent for your idea to work, or delaying one track by a few milliseconds might be enough... but the rule is they cant be the same!

Yes good point, had mentioned it in a bit longer version of the post and then edited it out :headbang:

@armans, you could look at the Rescue/RescueAE free plugin from Variety of Sound that essentially does the above in one move (the "width" knob on the side channel).
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby armans » Thu Nov 19, 2020 12:33 pm

Hugh Robjohns wrote:
armans wrote:
They might be dissimilar in their amplitude, their frequency content, or their phase/timing -- or all three. And it doesn't actually take very much dissimilarity to leave a lot of signal in the Side element.

but even if they ARE different in all these ways, there would still be some cancellation in the side channel wouldn't there? I mean they are playing the same chords in time with the music yet there is NO cancellation and the side channel yields a perfect mono guitar take!!
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby Hugh Robjohns » Thu Nov 19, 2020 1:18 pm

armans wrote:...but even if they ARE different in all these ways, there would still be some cancellation in the side channel wouldn't there?

Not necessarily that you'd notice. It really doesn't take much of a difference in level or timing/phase to reduce the nulling very dramatically and leave what appears to be an almost perfect track.
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby armans » Thu Nov 19, 2020 1:27 pm

Hugh Robjohns wrote:
armans wrote:...but even if they ARE different in all these ways, there would still be some cancellation in the side channel wouldn't there?

Not necessarily that you'd notice. It really doesn't take much of a difference in level or timing/phase to reduce the nulling very dramatically and leave what appears to be an almost perfect track.

hmmmm, let me take this all in.. but as Arnold says: I'll be back!
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby blinddrew » Thu Nov 19, 2020 2:39 pm

It's easy to have a play and experiment yourself. Take a mono track, duplicate it, pan one hard left and one hard right and flip the phase. Then add a delay to one track and see how quickly increasing the delay takes you out of full cancellation.
Alternatively, play through a chord progression a dozen times (to a click), take two rounds of the progression from the middle of that run so that they're most likely to be as similar as possible, split and pan as above and see how much cancellation you get.
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby armans » Thu Nov 19, 2020 6:13 pm

blinddrew wrote:It's easy to have a play and experiment yourself. Take a mono track, duplicate it, pan one hard left and one hard right and flip the phase. Then add a delay to one track and see how quickly increasing the delay takes you out of full cancellation.
Alternatively, play through a chord progression a dozen times (to a click), take two rounds of the progression from the middle of that run so that they're most likely to be as similar as possible, split and pan as above and see how much cancellation you get.

I tried both

1st suggestion:
This was very interesting. Just 1 milisecond takes it out of full cancelation and there is a very audible difference, but this kind of widening effect causes comb filtering in mono so it can't be useful can it?

2nd suggestion
I did a double guitar track as you mentioned and hard panned them, I then went to my decoder plugin and it is true that there is quite a lot of the guitar left in the side channel but in that side channel, the guitar sounds slightly "comb filtered" while in the reference track above, the resulting side channel of the supposed "two different guitar takes" is perfect without any comb filtering. This is what I was trying to say, I have done this on stereo guitars before and the side channel never sounds so good on its own, there is always a bit of "phasing".
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby Hugh Robjohns » Thu Nov 19, 2020 7:01 pm

armans wrote:This was very interesting. Just 1 milisecond takes it out of full cancelation and there is a very audible difference, but this kind of widening effect causes comb filtering in mono so it can't be useful can it?

Depends on the source material and how the comb filter notches fall on its harmonic content... longer (and shorter) delays have a less audible comb-filtering effect.

I did a double guitar track as you mentioned and hard panned them, I then went to my decoder plugin and it is true that there is quite a lot of the guitar left in the side channel but in that side channel, the guitar sounds slightly "comb filtered" while in the reference track above, the resulting side channel of the supposed "two different guitar takes" is perfect without any comb filtering.

This comes down to how similar the two parts are. There are ways around it such as by playing chord inversions, playing different rhythms (which is what I think is happening in your demo track), playing with different tunings, and so on...
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby armans » Thu Nov 19, 2020 10:00 pm

Hugh Robjohns wrote:
This comes down to how similar the two parts are. There are ways around it such as by playing chord inversions, playing different rhythms (which is what I think is happening in your demo track), playing with different tunings, and so on...
The guitars play exactly the same part on both sides. Flip between mid and side and you can hear it. If it is two different parts as you say, they are very tightly played.
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby Hugh Robjohns » Thu Nov 19, 2020 10:04 pm

Try listening to left only, and right only...
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby Kwackman » Thu Nov 19, 2020 10:20 pm

armans wrote:The guitars play exactly the same part on both sides. Flip between mid and side and you can hear it. If it is two different parts as you say, they are very tightly played.

No matter how tight the guitarist is, if he/she is recording separate left and right tracks, there WILL be differences.

To have nothing in the "S" signal, the left and right tracks must be IDENTICAL, i.e the same SINGLE recording copied to both tracks and their channels panned by the same amount. The two channels must have identical plug-ins (if used) with identical settings.
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