Phase Issue?

[metaljoseph]

What is a phase problem? I always hear people saying they have phase issues. What is that? How do you get by it? TY.

 

[mshilarious]

What is a phase problem? I always hear people saying they have phase issues. What is that? How do you get by it? TY.

A phase problem is where two similar signals are slightly out-of-sync with each other. When combined, they will interfere, causing peaks and nulls at various frequencies.

It is commonly caused by two microphones picking up the same source, but with one mic at a slightly difference distance. The time it takes the sound to travel the extra distance causes a phase problem.

 

[reshp1]

To see what it sounds like, put a delay of a few msecs on a track and mix it with the original. Play around with the delay times and notice how the frequency response of the combined tracks changes. It's a good idea to hear the phenomenon in person so that you can immediately identify it when you encounter it in a real world situation.

 

[treymonfauntre]

i've always wondered what exactly the phase reversal button does. what about mixers that don't have them? is there a digital way to fix it?

 

[bennychico11]

i've always wondered what exactly the phase reversal button does. what about mixers that don't have them? is there a digital way to fix it?

a phase (or polarity depending on who you ask) reversal switch flips the wave form on that track upside down 180 degrees. if you have two mics that are causing phasing issues this can sometimes help fix it. some software programs call it "inverse". if your mixer doesn't have one, you can always use a cable that has the wires attached to pins 2 and 3 switched on one side of the cable. if you've already recorded the signal you can use this cable and reroute it back into the recorder on a different track. the signal will go out of the mixer and be flipped back around.

 

[LuvMacheen]

More on phase

So does Phase ONLY occur when using 2 mics or can it occur on 2 totally unrelated tracks? Like 2 seperate guitar tracks????

 

[giraffe]

So does Phase ONLY occur when using 2 mics or can it occur on 2 totally unrelated tracks? Like 2 seperate guitar tracks????

it's theoretically possible, but not in a meaningful way.

 

[Track Rat]

Generally it only occurs with the same source being picked up by two or more mics, or a mono source with the very short delay as mentioned above. It doesn't happen BECAUSE you have two or more mics on a source, only that it's possible.

 

[XLR]

What is a phase problem? I always hear people saying they have phase issues. What is that? How do you get by it? TY.

Phase coherence of musical sounds in general is similar to a picture being in or out of focus. Musical sounds are naturally in phase... meaning the fundamental frequency and all the overtones are in sync with one another. Recording techniques and processing though can do things to the recorded version of the sound that pull various parts of the frequency spectrum out of phase with the rest, reducing clarity, richness and naturalness of the recorded sound. It's one of the characteristics of some high quality mic's that they are in phase in their pickup of sounds coming from the side as well as the front, and it makes a big difference. So even just a single mic can produce an out of phase sound if used certain ways.

With two mic's on a single source you can get a lot of time-alignment things going on, and with stereo mic'ing it can be a good thing... With a spaced pair, for instance, time arrival differences of both direct and room reflections between the mic's is what gives it its spacious sound... but the technique is intended for hard-panned stereo use. If the L and R are combined to a single channel, it creates a phase problem and will generally sound worse than each mic did alone. A lot of phase problems people have with multiple mic's on a guitar are the result of a similar kind of time-alignment thing.

Tim

 

[fraserhutch]

it's theoretically possible, but not in a meaningful way.

Then again, it could just be a phase we're going through

 

[tourettes5139]

Here's an animated example of phase cancellation (well not exactly, but I think it still applies) that my physics teacher showed me in class a week or two ago. It really helped me to see a visual representation of it. Yeah, its kinda geeky, but hey, who cares?

Phase animation

Scroll down to where it says "Two sine waves travelling in the same direction: Constructive and Destructive Interference" and that is it.

I apologize if I completely screwed it up, or if I confused anyone.

 

[Farview]

Kick ass link. If you scroll down further, you can see what happens with harmonies.

 

[Track Rat]

That's excellent.

 

[XLR]

tourettes5139, yeah that's excellent. Thanks.

Tim

 

[Gorty]

Very interesting, it's great seeing animated explanations.
Good stuff Tourettes

 

[tourettes5139]

No problem!!