Farview said:
How many times can this myth be repeated on the board in two days?
The 3 to 1 rule doesn't work for and was never meant to apply to a close mic-far mic situation. Ever!!!!
The 3 to 1 rule is about attenuation,
not phase cancellation. You would use the 3 to 1 rule when you are micing an
acoustic guitar (and both mics are the same distance from the guitar) 1 mic at the bridge and 1 mic at the neck. It also applies to micing two diferent sources.
sorry never noticed that someone else posted this.
phasing does result in attenuation, though. When the out of phase signals (out of time signals) are summed together certain frequencies cancel creating a comb filtering effect. The frequency response of this comb filtering creates peaks and dips in our sound, attenuating the sound at that moment in time. Separating by AT LEAST 3 times the mic-to-source distance creates a level difference of 9dB or more in turn reducing the comb filtering dips to an inaudible 1dB or less....we aren't trying to completely eliminate the comb filtering, just trying to lessen the effect. Also at this distance (some suggest a 4:1 rule) the second mic can pick up enough room ambience to minimize any phase issues.
Using the 3:1 with a guitar when micing the neck and body is the same thing as micing the cabinet with a close and far mic, in my mind. In the
acoustic guitar example, the neck mic is the far mic in relation to the body. It's still a further distance away from that sound source than the close mic is. You just want to eliminate any phasing from body to close mic and from body to far mic. True, 3:1 is better used when recording two different sources and you want to minimize bleed from other sources (ie. snare mic and tom mic).
However, we don't live in a world with perfect sine waves. The wave form bouncing of the ground, wall, mic stand of the first mic, etc. change the way it sounds in the second mic...which is one of the reasons why we use a close mic and a far mic. It's the same sound coming from the amp, but the second mic might give us a better result after the wave form has had time to develop. Don't treat each of the mics as if they are recording the same source, treat them as if they are recording two different sources...because they actually are capturing two diffrent sounds.
I did say that the 3:1 may not always work for what you are recording, depending how much of the sound and from where the reflections are coming from. Use you ears. It sounds like it's not working for you, so try the sliding of regions thing I suggested....I prefer that method anyway. 3:1 has worked for me, but moving the wave form is the only way you can actually correct the phase of the two waves.
The 3:1 has never been an aboslute rule. It was mainly used in situations where you had to quickly setup two mics or wanted to see if maybe two microphones would work well for what you might be recording.
http://www.crownaudio.com/mic_web/tips/mictip6.htm
