Recording 101/4 - A really quick look at Phasing

Well, with work being crazy at the moment due to the December rush, I haven't had time to look at the next installment for Recording101. So I thought I'll give a quick explanation regarding phase and the 3-1 rule when double micing an instrument.

The basic idea is that if you for example want to double mic a snare drum and the top mic is 1 cm away from the shell, then mic 2 which will probably be at the bottom should be 3 cm away. This in theory is somehow correct if you would have a single frequency from the instrument.

The reason the 3-1 rule is not always the right idea is because of basic physics. So join me on a stupid trip down High School physics. When you have 2 waves moving towards each other a couple of things can happen. One is that the wave can completely 'disappear', it can also double in height.

Now if you look at fig.2 you'll see that where the wave is 'in phase' the height of the wave doubles, where as if its slightly out there is a dip at certain points.

Now if a snare for example was just one frequency you'd be fine with just the phase invert switch and the 3-1 rule. But because of the complex nature of instruments harmonics this doesn't always work, because there will ALWAYS be phasing issues. The idea is then to find what is the 'root' HZ of that particular instrument or sound source.  This is where your ears come into the picture. LISTEN!! What helped me most when setting up a mic pattern for drums, or multi-micing guitar amps was to use headphones, and then positioning them in the live room whilst the muso was jamming away.

Phasing and multi-micing always becomes quite an issue, especially if you're in a small room with a lot of reflections.
It, however, always comes down to what sound you're looking for.

The voices in my head are calling again, so I guess it's time to sign off and disappear into the dark void that is my studio.

For a nice read, follow the link below.. Always a nice journey to have a look inside the head of some of the best in the industry..

http://www.soundonsound.com/sos/jul05/articles/qotsa.htm