3:1 Rule

Phase peaks and dips from the same sound source occur when panned to the same position at the same level, which will be the case using more than one microphone. A rule-of-thumb for minimizing phasing issues is to have around 10 dB level difference between the microphone contributions. The 3:1 distance rule addresses this need. Another workaround is to pan microphones in the mix, which will, by the nature of panning, also create level differences.