Microphone Placement

Microphone placement?  I just put the mics in front of the performers and everything seems fine.  What more do I need to know?  Well, as outlined in the book How Recording Works from the Recording Institute of Detroit, there are a few things you should pay attention to:

1.  Proximity Effect – Defined as an increase in bass frequency output when the mic is placed a foot or less away from the instrument.  When placed 1/4 inch away from an instrument, the low-bass frequencies are picked up about four times louder than they should be.  This will basically sound like you have turned the bass control on a stereo up all the way.  Even if the instrument sounds good, the proximity effect will make a recording sound muddy.  Some microphones have permanent or switchable “bass roll-off” which should be engaged when placing a mic closer than around 8 inches from your sound source.

2.  Phase Cancellation — Two sound waves are “in phase” when the peaks of the two waves occur at the same time.  This results in an audio signal with twice the strength of one.  “Out of phase” occurs when the peak of one wave occurs at the same time as the valley of another.  These signals will cancel each other out when mixed together.  Phase cancellation frequently occurs when multiple microphones, placed in too close of proximity to one another, are in use.  Use the Three to One Rule to help avoid this problem.

3.  Three to One Rule — A second microphone (intended for another voice/instrument) must be placed three times further away than the microphone is from the sound source.  If you are micing two singers and your first mic has been placed 8 inches from the first singer, then the microphone for the second singer must be at least 24 inches away from the first microphone.

Whether working with top-of-the-line equipment or dents and dings, keeping these useful tips in mind can make a world of difference when micing your performers!

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