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Can you EQ two tracks from a coincident pair mic capture differently?

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Can you EQ two tracks from a coincident pair mic capture differently?

Postby armans » Tue Jan 12, 2021 10:15 am

Primarily on an acoustic guitar if I use a coincident pair or work hard at getting my two microphones in phase when recording, would EQing them seperately be a no-no or is it ok to do this? I understand that you would be changing the phase relationship between the two right?

also, if I have a mono guitar recording and EQ the L and R channels seperately, am I also creating phase differences between the two channels? Can this be used to creative effect by making a mono track seem wider?

Perhaps I should explain what I am trying to do as well so that maybe someone could help me achieve my goal. Lets say I want to record guitar congas and bass and a vocal. I would like the guitar to occupy most of its frequency range on the left side but on the right side, I would like the congas to have the midrange with the vocal and have the guitar very thin sounding so that the vocal is clearer in the stereo mix. So basically on the one side mostly guitar, vocals and bass and on the other side congas, vocals and bass with a small piece of the guitars frequency coming through. I am thinking I could record the guitar with two mikes and just EQ the side with the congas and vocals differently so if this is good practice then great.

thank you!
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Re: Can you EQ two tracks from a coincident pair mic capture differently?

Postby CS70 » Tue Jan 12, 2021 10:41 am

It's ok. Pretty much every EQ introduce some phase shift (and if they don't, it's some other artifacts), but don't take phase differences as a problem as an absolute: when signals sum up, all that means is that the filtering that occurs will change the timbre... it's a problem only if it changes the timbre in an unpleasant way.

Sure, if the signals are identical, it's likely that for a large range of shifts (i.e. time delays) the result will be comb filtering, that usually doesn't sound good.

But when you equalize, the signals won't be identical anymore so the result of summing them can be good or bad.. your ears being the judge. The harder you EQ, the more the signals will be different, but it's really about trying and listening, not absolute rules. Heck, even comb filtering can be used as an effect in some cases - if the objective is a hollow sound.

It's really a matter of trying and listening, as usual, theory will bring you only so far.
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Re: Can you EQ two tracks from a coincident pair mic capture differently?

Postby Hugh Robjohns » Tue Jan 12, 2021 11:08 am

armans wrote:Primarily on an acoustic guitar if I use a coincident pair....

If you are using a coincident pair to capture accurate stereo -- such as recording a string quartet, say -- then the two channels have to be treated identically or you will mess up the stereo imaging.

But if you are using two mics located coincidentally purely to maintain time alignment in front of a single source, like a guitar, it doesn't really matter what you do with them.

Yes, changing EQ will generally introduce phase shifts but they are unlikely to cause significant problems.

armans wrote:Lets say I want to record guitar congas and bass and a vocal. I would like the guitar to occupy most of its frequency range on the left side but on the right side, I would like the congas to have the midrange with the vocal and have the guitar very thin sounding so that the vocal is clearer in the stereo mix. So basically on the one side mostly guitar, vocals and bass and on the other side congas, vocals and bass with a small piece of the guitars frequency coming through.

I think I'd pan the vocals and bass central, the guitar left, the congas right, and let the room reverb (real or artificial) fill out the rest...
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Re: Can you EQ two tracks from a coincident pair mic capture differently?

Postby armans » Tue Jan 12, 2021 11:28 am

CS70 wrote:It's ok. Pretty much every EQ introduce some phase shift (and if they don't, it's some other artifacts), but don't take phase differences as a problem as an absolute: when signals sum up, all that means is that the filtering that occurs will change the timbre... it's a problem only if it changes the timbre in an unpleasant way.

Sure, if the signals are identical, it's likely that for a large range of shifts (i.e. time delays) the result will be comb filtering, that usually doesn't sound good.

But when you equalize, the signals won't be identical anymore so the result of summing them can be good or bad.. your ears being the judge. The harder you EQ, the more the signals will be different, but it's really about trying and listening, not absolute rules. Heck, even comb filtering can be used as an effect in some cases - if the objective is a hollow sound.

It's really a matter of trying and listening, as usual, theory will bring you only so far.

Thank you!
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Re: Can you EQ two tracks from a coincident pair mic capture differently?

Postby armans » Tue Jan 12, 2021 11:30 am

Hugh Robjohns wrote:
I think I'd pan the vocals and bass central, the guitar left, the congas right, and let the room reverb (real or artificial) fill out the rest...

Good suggestion. I will try a room mic. Thanks!
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