Out of phase mics!!!???

[lurgan liar]

Ok mics being out of phase .....i don't get what the problem is ...?

lets say you were recording an acoustic guitar using 2 mics? 1 on the 12 th fret and the other on the bridge ...each about 1-2 foot away from the guitar ....then u hit record .......

so u playback ...and they are out of phase.......why not move the 12th fret guitar track forward a few milliseconds and they will then be in phase....????

Or have i completely lost my marbles ...can someone please explain why, what i just said is wrong???

Thanks in advance

 

[bennychico11]

okay....now do this for me on an analog tape machine?




and if you never ever plan on using analog....try this with other instruments playing in the room. say the guitarist also sings when he plays. now the 12th fret mic is delayed with the vocal mic. always always check your phase on any two mics. why fix it later when you can fix it now?

 

[reshp1]

Consider the guitar as a stereo instrument. There is sound coming from the 12th fret area, and from the bridge area. The problem is not only is the sound from the bridge of the guitar getting to the 12th fret mic later than the bridge mic, but the sound from the 12 fret is also reaching the bridge mic later than the 12 fret mic. Which track do you shift? You can put one sound source in phase with itself, but then the other would be made worse.
The way around this is to use the 3:1 rule, meaning the mics have to be 3 times closer to the source they are capturing as the source the other mic is capturing. I.E. Mic A 3 times farther from source B than source A, mic B three times farther from source A than source B. That way the sound of source B in mic A is much weaker than it is in mic B, and the sound of source A in mic B is much weaker than it is in mic A. Blended together, the weaker signal does not interfere strongly with the stronger signal picked up by the other mic.

 

[Farview]

The 3 to 1 rule applies to mics that are recording different sources in the same room. It has nothing to do with multi-micing one instrument and will do nothing to the phase coherence.

If you can't get rid of the phase problem by reversing the polarity of one of the tracks, you need to do it over. If you can't do it over, anything you do will be a compromise. You will have to use the method that ruins the sound less than the others.

 

[daav]

If the mics are the same distance from the single source won't htis help quite a bit? Will this be effective the A/B technique with the 12th fret/bridge if you are careful to try to keep them about the same distance from each other and a central point on the guitar, say, the sound hole?

This is a good one, i am still fuzzy on this topic.

Daav.

 

[reshp1]

The 3 to 1 rule applies to mics that are recording different sources in the same room. It has nothing to do with multi-micing one instrument and will do nothing to the phase coherence.

If you can't get rid of the phase problem by reversing the polarity of one of the tracks, you need to do it over. If you can't do it over, anything you do will be a compromise. You will have to use the method that ruins the sound less than the others.

Within a foot of an acoustic guitar, I consider the sound coming off the 12th fret and the sound coming off the bridge/soundboard to be different sources.

 

[Farview]

You are missing the point of the 3 to 1 rule. You are supposed to have the mics 3 times farther apart than they are to the source. If you have them 1 foot from the source, they would need to be 3 feet away from each other. Unless you have a really big guitar, it won't work.

The 3 to 1 rule is to eliminate bleed between 2 different instruments. The only reason it eliminates phase at all is because it reduces the delayed bleed of one instrument in the other instruments mic.

 

[FALKEN]

all you have to do is put on headphones and move the 2 mics to where they sound the best. that will get you a better sound than shifting the files.

 

[mixsit]

I aggree with everything said here. (Grin) No really.
Bottom line is if both are the same distance from the guitar they are both getting the majority of their signals in time with a bit of out out time cross feed. This can sound fine and fits a very valid stereo mic tecniquic that's strong point is the nice phase effects it causes.
--Name that mic tecnique and why it does what it does...
Wayne