3 to 1 Rule
From WikiRecording
3 to 1 Rule
A general rule for minimizing phase problems when using multiple microphones is to use the 3 to 1 rule. Generally speaking when using multiple microphones set one microphone 3 times the distance of the other microphone from the sound source. So, if one mic is 2 ft from a sound source, the second will be 6 ft (2ft x 3 = 6). Once again, this technique is used to prevent phase problems between the two mics.. This rule only applies to direct miking of instruments, room miking generally greater than 3ft+ from a sound source minimizes or uses phase to its advantage depending on the technique.
The image on the left shows the 3 to 1 rule with only one sound source, while the one on the right shows it with two sound sources.
External links
http://www.sweetwater.com/expert-center/glossary/t--3:1Rule Sweetwater Article about the 3:1 Rule.
