Microphone Phase Relationships

  • Thread starter Thread starter Chewie
  • Start date Start date
Think of a sinewave. Now flip it upside down and add it to itself. You'll see that as one goes positive, the other goes negative and vice versa, essentially cancelling each other out. Well essentially this is what's happening when you record both sides of the drum. When the drum is struck, the head struck moves inward, the head on the opposite side moves outward. If you add the sound of the mics on each side you get a lot of cancellation. So you want to invert the waveform on on of the mics, so the signals aren't "fighting" with each other. That's what phase reversal is simply, flipping or inverting the phase.

You also get phase problems from mic'ing the same source from different distances (like the snare mic, and the Hi hat mic picking up the snare). That's because it takes sound a different time to travel to one mic than the other. Phase relationships are more complex in this case because the constant delay time puts some frequencies in phase and some out of phase. Inverting phase on one of the signals can move the cancellations to a less noticable frequency, but the best way to solve this problem is by mic placement.
 
You can also correct some mic phase problems with delay or by switching the (+) and (-) on the mic cable (usually pins 2 and 3).

PS... when two mics are out of phase you hear a loss of lows... and kind of a hollow swishing sound.
 
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Ok.

DJL said:
You can also correct some mic phase problems with delay or by switching the (+) and (-) on the mic cable (usually pins 2 and 3).

PS... when two mics are out of phase you hear a loss of lows... and kind of a hollow swishing sound.
Click to expand...

How else can I do this?
 
Chewie said:
Ok. I know this has been covered a lot but I still don't get it. i remember from physics constructive and destructive interations but I've been reading
http://www.saecollege.de/reference_material/pages/placement.htm
and I still don't get it. Especially when e talks about phase reversal.
What is phase reversal?
How do you know when it is required?
How do you it?
Click to expand...

Phase reversal is non-existant. What they are talking about is POLARITY reversal. Big difference.

READ. And make sure you follow the links in my first post.


Light

"Cowards can never be moral."
M.K. Gandhi
 
Chewie said:
How else can I do this?
Click to expand...
Here's two more ways you can do it.

1) Use good mic placement (3/1 rule).

2) Use only one mic per sound source.
 
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