Phase Issues From Two Separate Recordings

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darknight

New member
I'm pretty new to recording but I thought I had guitar-related phase issues sussed in my DAW (Reaper) as well as a reasonable idea of how to minimise phase cancellation when setting up two microphones.

Now i've found something that has me absolutely stumped:

I recorded a track on a classical guitar, Rode NTA1 placed about 2 feet from the guitar. I then recorded an additional part exactly the same (going for this type of effect:https://www.youtube.com/watch?v=5WvWkUhszeE) and on playback in mono there were phase issues (severe comb-filtering in a later set of takes I did). I've never had phase issues when recording two identical but individual guitar parts. What can I do to fix this? My usual act of moving the waveform in the DAW doesn't seem to be working like it does when I mic my amp up (for example) with two mics and get a little latency, i guess because the waveforms aren't identical. Any advice out there on this?

Having played around with a few trial versions of phase alignment plugins i'm starting to think that I need to address the issue earlier on in the process...
 
I used the phase inverted button in my DAW, if that's similar to what you mean?

It doesn't seem to solve the issue because the waveforms aren't identical, so if it fixes a small section it may not be a fix for the whole passage. This makes me think that I should try different mic placements between takes when tracking.

This is really baffling me.
 
This sort of thing just happens every once in a while. Is the recording destined to be listened to in mono?

Moving the mic between takes will help this. It is caused by being too precise from take to take. It's hard to combat because each note is a little different, yet close enough to cause comb filtering.
 
bouldersoundguy said:
Something about this makes me think "all pass filter".
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Worth a shot, but that's probably what the "phase alignment" plugs mentioned in the OP do... I think, since it's kind of moving target, it can't really help. I mean, it might help one part, but make another worse, just like anything else you might try.

Theoretically, if you slide one far enough, it should push the comb filtering out of the audible band. You might try sliding one back a millisecond or two, and the other forward a millisecond or two so that they average out to be on the beat. That might just make it sound sloppy, but if nothing else is helping, it's worth a try.

Better would probably be to not play exactly the same thing on exactly the same guitar to begin with. Either change the part or change the instrument or both. I think even maybe if you like tuned down a step or so and then capoed up to compensate, it should change the way the harmonics set up, and get you some relief.
 
Yeah, if it's tuned and played precisely it's going to have audible phase interactions one place or another. I hadn't thought about tuning down and capo-ing up, but I was going to suggest playing in a different position on the neck. Here's an idea, use a different guitar.
 
ashcat_lt said:
Worth a shot, but that's probably what the "phase alignment" plugs mentioned in the OP do... I think, since it's kind of moving target, it can't really help. I mean, it might help one part, but make another worse, just like anything else you might try.

Theoretically, if you slide one far enough, it should push the comb filtering out of the audible band. You might try sliding one back a millisecond or two, and the other forward a millisecond or two so that they average out to be on the beat. That might just make it sound sloppy, but if nothing else is helping, it's worth a try.

Better would probably be to not play exactly the same thing on exactly the same guitar to begin with. Either change the part or change the instrument or both. I think even maybe if you like tuned down a step or so and then capoed up to compensate, it should change the way the harmonics set up, and get you some relief.
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I've never used an all pass filter but i guess it's worth having a mess around with it.

I'd like to change the instrument but i'm going for a stereo sound with almost identical guitar sounds on each side (like example video) so I feel like changing to a steel string guitar (for example) would unbalance everything. I think I want too much...

I like the capo idea though, good call.

Farview said:
This sort of thing just happens every once in a while. Is the recording destined to be listened to in mono?
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Hard-panned stereo rather than mono, i only noticed the issue when summing to mono for eq'ing purposes. Ideally it would be listened to with headphones but I don't think I get to be that demanding so I'd like to put something together that can be listened to in any format without phase issues coming into play.
 
Since there are hundreds of ways the end user can screw up the sound with their choice of playback devices and decisions, at some point you have to let go of trying to make sure it sounds great in every possible situation that someone could put it in.

Yes, your song could sound crap in someone's fisher price Winnie the Pooh cassette player, but that isn't your fault.
 
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@ashcat
Sound Radix Auto Align
MAuto Align
Voxengo PHA-979

All trial versions, i'm on an old Mac which limits options i expect...The auto-ones are probably more useful when you have two identical but out of phase waveforms...but then not really worth the price if all they're doing is bumping them in phase as this is pretty easy to do in the DAW in my experience.

Voxengo is manual but i think because the waveforms aren't identical all the way through any improvements are temporary. I'm getting the feeling that it's too late to address the issue once i've recorded the parts :(

^ this is true, I was just amazed when I put songs with similar classical guitar panning in mono and couldn't hear phase issues when it's so prominent in my own recording. I guess my aim should be to get it sounding reasonable across a few different playback devices e.g. monitors, headphones, car speakers and laptop speakers.
 
Oh yeah no! Sorry, those are different from what I was thinking. I was envision things like PhaseBug that emulate the hardware In Between Phase boxes. The ones you used try to figure out the delay and then correct for it.

It can't be sure to help either way precisely because (as you've surmised) it's a moving target. It's possible that enough all-pass stages could just confuse everything enough that you don't hear the deeper notches all that often.

Have you tried just scooching the one over to see if there's a point where it doesn't sound like phase but it doesn't yet sound like flam? It might make one guitar feel a little further away, but it might help.

If one of them was a little quieter than the other, the notches wouldn't he so deep.

How much reverb is on your reference tracks. A good spray of reflections might smear everything just enough, too.

Edit - Thinking about it more, if you are actually good enough to get close enough to have this problem, I think it's likely that if you actually monitored in mono so that you could hear the phasing while playing, you'd pretty intuitively figure out how to minimize the effect or at least make it more consistent so nudging and other tools had a better chance of helping.
 
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