Out of Phase Guitar Tracks?

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Captain Whisky

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So I think that I understand the concept of being out of phase and that if one waveform is 180 degrees out of phase with another then one of them will need to be reversed correct?

But what about if it is only slightly out of phase? Take a a look at these two guitar tracks that don't seem to match up perfectly. Are they out of phase and is this significant enough that it should be corrected?

View attachment 83082
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Thanks ;)
 
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No pic.

Is this two mics on one source? If so, yeah you can get an out of phase scenario. The remedy? You can zoom way in the DAW and slide one to match the other. Or, drop one way lower than the other so acts as a "thickener". Or flip the phase on one track and drop it. It can be fixed.
 
Can you not click the link that says Attachment 83082? It should be there ;)
Yeah tthis is two mics on one guitar amplifier, is this important enough to fix? I mean will it make much of an difference sound wise if it is corrected? What did sound engineers do back in the day before they could edit waveforms with such ease?
 
The thing is that different frequencies are more out of phase than others, and will cancel more completely. It will cause dips and peaks in the frequency response called comb filtering.

It's really only a problem if it's a problem. You just need to use your ears. If you can't mix them together and get anything useful then you may need to nudge. Or just pick one...
 
The old school engineers made sure that the mics were exactly he same distance from the speaker.

Now, as far as fixing it goes, how does it sound? If it sounds great, don't mess with it. If I were you, I would move the one to match the other and see if that sounds better or not.

Btw, if you are using two of the same Mic, its kind of a waste of time since they should sound the same.
 
ashcat_lt said:
The thing is that different frequencies are more out of phase than others, and will cancel more completely. It will cause dips and peaks in the frequency response called comb filtering.

It's really only a problem if it's a problem. You just need to use your ears. If you can't mix them together and get anything useful then you may need to nudge. Or just pick one...
Click to expand...

Farview said:
The old school engineers made sure that the mics were exactly he same distance from the speaker.

Now, as far as fixing it goes, how does it sound? If it sounds great, don't mess with it. If I were you, I would move the one to match the other and see if that sounds better or not.

Btw, if you are using two of the same Mic, its kind of a waste of time since they should sound the same.
Click to expand...

Yup, what these guys said.
 
Captain Whisky said:
So I think that I understand the concept of being out of phase and that if one waveform is 180 degrees out of phase with another then one of them will need to be reversed correct?
Click to expand...
Reversing is absolutely the solution if the recordings have opposite polarity.
With phase you can be 180 degrees out at a particular frequency.
That means you're out by different degrees at other frequencies.

These guys are bang right. Flipping polarity or nudging on the timeline may help in your scenario, but it may not.
It's down to using your ears and making the choice based on your preference.
 
Thanks for the replies, very informative ;)

I have thought about trying to get the mics at the exact same distance from the speaker but it can be difficult as you often can't clearly see where the diaphragm is on many microphones. Is it something that most of you would look into correcting when mixing? I guess it more important to correct for example two overheard mics to get the drums sounding tighter, right?
 
I suspect there aren't many hear who make time corrections. They certainly wouldn't do it just because.
The most likely thing is that most don't know if their waves line up perfectly and don't care.....They just know they moved the mics until the guitar sounded good.
Focus on that and you won't go far wrong.

With overheads it's a different thing because you're dealing with a stereo image.
If you're aiming for the snare and kick to be central, then overhead placement is critical.
I usually measure those with a tape or a length of cable to make sure the snare and kick are equally space from each overhead.

Of course if you're using some other technique then forget the above.
 
What they said :)
when doing mic placement make sure you monitor the mics not the amp too.
 
Captain Whisky said:
Thanks for the replies, very informative ;)

I have thought about trying to get the mics at the exact same distance from the speaker but it can be difficult as you often can't clearly see where the diaphragm is on many microphones. Is it something that most of you would look into correcting when mixing? I guess it more important to correct for example two overheard mics to get the drums sounding tighter, right?
Click to expand...

But there's the other way to look at it....why have both mics exactly the same distance? Why not put one 2" from the cab, and the other 12" from the cab...? :)

I would only really worry when the tracks get to 180 degrees out of phase, because then the frequency cancellations will be most dramatic, but it's all about *how it sounds* not how it looks in the DAW or how they measure with a yardstick.
The slight time-delay can actually give you a more thicker sound, which may be just what you want...so really, put the tracks up, mess with their levels and panning to what you think is right, then for shits-n-giggles, check mix in mono just to hear if the guitars really drop out badly....otherwise, if it sounds good, leave it alone.

Some people just get too crazy about aligning every track. Nothing really sounds like that in real world, live situations.
 
When the track from mic 1 is 180 degrees out of phase with the track form mic 2....as in the positive cycle of soundwave one is directly opposite the negative cycle of soundwave two. Like say, if you mic the front and back of a cab.

Isn't that what this thread is about....phase issues....or haven't you been paying attention?

Here...this might help:

3463_polarity_phase_09.gif
 
Steenamaroo said:
Reversing is absolutely the solution if the recordings have opposite polarity.
With phase you can be 180 degrees out at a particular frequency.
That means you're out by different degrees at other frequencies.
Click to expand...


Your example only demonstrates the effect at one particular frequency.
No other frequency will be 180 degrees out of phase with the same delay applied.
 
Yeah, no. The front and back of a speaker will be opposite polarity, which will put all frequencies out of phase. Same with like a top and bottom snare situation. (Though neither scenario will actually be perfect IRL...)

That's not really what we're talking about here, nor what your little graphic shows. Your picture shows exactly one frequency picked up by two sources which have exactly enough delay to be 180 out AT THAT FREQUENCY. No other frequency will be exactly 180 out with that given delay.

The OP's picture is also a delay between two tracks. It will also have exactly one frequency 180 out.
 
This is it. ^^

That's why flipping polarity may or may not be helpful.
Doing so will strengthen a fundamental frequency and its multiples, and weaken other frequencies to varying degrees.

That fundamental frequency is dicated by the distance between the two mics.
 
Right.... a typical audio signal is not a sine wave like in the diagram (which is just to demonstrate what 180 degree out-of-phase looks like)...but when using two mics on front/back cab, or kick drum, or top/bottom snare the two tracks are out of phase 180 degrees for all frequencies, and will cancel if the polarity is not reversed...which is what I said.

With time-aligning two tracks you have varying degrees of phase shift for various frequencies, so where you slide one track relative to another will not make all frequencies equally out of phase, but at some points the differences between them will go from that deeper phasey sound to more of just a delay effect with minimal noticeable phase issues.
What works or doesn't work is up to the mixer.

So what's "yes and no"....???

Seems to me like we are all saying the same thing one way or another....unless someone wants to nit-pick. :D
 
miroslav said:
Right.... a typical audio signal is not a sine wave like in the diagram (which is just to demonstrate what 180 degree out-of-phase looks like)...but when using two mics on front/back cab, or kick drum, or top/bottom snare the two tracks are out of phase 180 degrees for all frequencies
Click to expand...

They're not. Phase is a related to time/distance..
The kick drum/cab thing exemplifies opposite polarity, which is not.

Place a mic above a snare 10" away, and one below 14" away.
You have opposite polarity AND a phase discrepancy. Two different things.


miroslav said:
unless someone wants to nit-pick. :D
Click to expand...

It's hardly nitpicking. If your diagram illustrated opposite polarity, it'd look like this.

Screen Shot 2013-10-30 at 02.14.45.png
 
Well....ashcat said the same thing: :D

The front and back of a speaker will be opposite polarity, which will put all frequencies out of phase. Same with like a top and bottom snare situation.
Click to expand...

Again....to simplify the explanations, I used the the sine wave diagram. When polarity is reversed or when it's moved a half-cycle opposite from it's copy....it's the same thing in both cases....180 degrees out of phase.
Because sine waves have only one partial, inverting the polarity of a sine wave produces the same result as shifting it 180 degrees out of phase.
I think we already covered the point that most audio signals are complex and basically made up of many "sine waves", so not all frequencies will be out of phase the same amount, at the same time.

If you want to drive home the point that polarity is about positive & negative voltages rather than time differences (phase)...fine. I'm just talking about the net result....how it looks & sounds, and when it will start to cancel out and/or go "phasey" more or less.

I don't think we have to qualify each post comment/statement with extensive definitions.
I assumed we all knew the textbook definitions, so no need to challenge every word. :)
 
I don't see the point in blurring definitions for the sake of simplicity.

If you were the first guy to reply that'd be cool, but your post seems to try to contradict the information that's come before it.
That's why I followed up.
 
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