Whats are phase issues and how are they caused?

T

TylerDrums109

New member
All i know is that they happen when using two microphones withing close proximity of each other...other than that this concept has eluded me....please explain?
 
sound hits each mic at a diff time, this is where the problem is. normally when 2 mics are in phase, you can zoom in on the wave forum and see that both tracks will rise and fall at the same time. this makes a thick full sound... in other words its "in phase" if the mics are spaced in a way that is "out of phase" you can see, with the two wave forums created, that one will rise as one falls... so they look like they are mirroring one another. this "out of phase" recording will sound thin and less loud. the two mics actually work against one another and you lose certain frequencies. you'll need to move the mics until this is no longer an issue, or flip the phase on one of the mics to get rid of that "mirroring wave forum"

hope that helps
 
SuaveRecords said:
sound hits each mic at a diff time, this is where the problem is. normally when 2 mics are in phase, you can zoom in on the wave forum and see that both tracks will rise and fall at the same time. this makes a thick full sound... in other words its "in phase" if the mics are spaced in a way that is "out of phase" you can see, with the two wave forums created, that one will rise as one falls... so they look like they are mirroring one another. this "out of phase" recording will sound thin and less loud. the two mics actually work against one another and you lose certain frequencies. you'll need to move the mics until this is no longer an issue, or flip the phase on one of the mics to get rid of that "mirroring wave forum"

hope that helps
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Ok now i sort of understand the concept of it...but how do i avoid it...and how can i know if my mics are in phase?
 
you know by either hearing how thin and weak it sounds. or by doing a test recording. zoom in on the wave forums that each mic has made. and look to see if the rise and fall at the same time. if they are not rising and falling at the same time, then you are out of phase. move the mics around until this no longer happens...another way is use head phones while placing the mics and have teh person play, move the mics untill you get a full sound. if you notice a spot where the sound is extra thin...this would be a place where your mics are out of phase... avoid that placement :P lol
 
SuaveRecords said:
you know by either hearing how thin and weak it sounds. or by doing a test recording. zoom in on the wave forums that each mic has made. and look to see if the rise and fall at the same time. move the mics around until this no longer happens...another way is use head phones while placing the mics and have teh person play, move the mics untill you get a full sound. if you notice a spot where the sound is extra thin...this would be a place where your mics are out of phase... avoid that placement :P lol
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Ah so its not a matter of distance the different mics are from the source? or from each other?
 
kinda both lol. usually you can use a 3 to 1 rule. the mics should be 3 times the distance from each other as they are from the sound source
p.s. re-read my last post i edited it, i was typing to fast and missed some stuff lol
 
SuaveRecords said:
kinda both lol. usually you can use a 3 to 1 rule. the mics should be 3 times the distance from each other as they are from the sound source
p.s. re-read my last post i edited it, i was typing to fast and missed some stuff lol
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What if the mics were different distances from the source?...sorry about all the questions i really appreciate the help though im starting to get it
 
it all really depends. like, if you set up mics on an acoustic guitar, and its all in phase, and it sounds great... you'll be fine, but if you move one mic, your probably not going to be in phase anymore. ooorrr maybe you just move the guitar.. like if the guitarist decides hes going to move back a foot or two, that might throw you out of phase as well. the two mic and teh sound source all play a part.
 
p.s. there is always more than one placement that could work, and be in phase. but there are a tone of placements that will be out of phase as well. so its really just a matter of trial and error.
 
SuaveRecords said:
p.s. there is always more than one placement that could work, and be in phase. but there are a tone of placements that will be out of phase as well. so its really just a matter of trial and error.
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I see well thank you for all the help...i think i will just at first stick to the 3 to 1 rule then move my mics checking to see if my movements bring them out of phase or not...again thank you
 
The 3:1 rule is most commonly called upon when miking two sources (e.g. a vocal and a guitar) with two mikes, with each assigned to one of the sources.

A mike (mike A) pointing at a mouth will pick up some of the guitar. A mike (mike B) pointing at the guitar will pick up some of the voice.

Because mike A is a different distance from the guitar that mike B is, there is the potential for phase problems to arise.

The 3:1 rule applied in this example would mean something like:

If both mikes are 30cm from their respective sources (voice and guitar), then the mikes should be 90cm away from each other.

What this does is ensure that the spill from the second mike is low enough not to affect in any significant way the sound from the first mike. So if mike A is capturing the vocals, the vocals that mike B picks up will not be so loud as to cause phase problems when you mix these two together.

Phase problems lurk when multiple mikes are used to mike multiple sources (a good example is a drum kit).

However, the 3:1 rule is not so critical when using two mikes to record a single, point source. Here the important thing is to keep the mikes equidistant from the source. This can be a little tricky when stereo miking a guitar, because a guitar, though a single instrument, is not a single point source of sound . . . the sound issues from the whole of the guitar. I wouldn't be too fussed about this.
 
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