Continuing the “no more source of confusion” series, here’s something I recently watched and found very interesting and very confusing about phase: Andrew Scheps, a big name in the audio engineering world department, talks with recordproduction.com about his approach when recording drums.

At 2′ 46” he goes into detail about specific choices for specific sources:

“Standard kick inside and outside, and if I had to pick something I suppose AKG D-112 inside and 47 FET outside”

“Is that just inside?” asks the moderator.

“Just barely inside, yeah, because… Two reasons: I’m usually not recording things like Pantera where you need to have a very clicky kick drum, so I like to have more low end in that inside mic; and also that keeps the inside and outside mic lined up, so phase-wise you’re only an inch or so apart which at the low frequencies doesn’t matter at all as opposed to being maybe a foot apart if you really stick that mic far inside“.

I am perfectly OK with the first reason but the second one I find confusing.

Because:

1. it is absolutely not a given fact that two almost-lined-up microphones are in phase, especially when they are one dynamic and one condenser;
2. the lower the frequency, the lighter is the comb filtering resulting from changing the distance of two non-coincident microphones: 80 Hz has a wavelength of 4,25 meters or 13,94 feet: a foot or so doesn’t change much proportionally whereas 200 Hz (low-mid frequency) has a  wavelength of 1,7 meters or 5,57 feet: a foot or so has a much more heavy impact on the phase of that frequency

Also when talking about phase, a reference to the target frequency should be mandatory.