phasing questions...

[Edson]

When recording with more then 1 mic in pro tools is there anyway to check the phasing and correct it if it's a little off??

Any engineers have recomendations in phase cancelation? does phase cancelation happen in the air, or is it simply when 1 mic capture's the sound before another mic does?

Thanks,
edson

[Park Seward]

In a perfect system, when the mic's diaphram moves back, the speaker in the system would move back also. You will find polarity problems caused by mic pres, miswired cable, older equipment with pin 3 hot, inverting opamps, and miswired speakers.

Some say they can hear the difference on one mic when speaking into it. The failsafe way is to use two mics together and see if sound cancels or is increased when the two mics are mixed together.

You will hear phasing when moving two mics apart from a sound source. The time delay will cause phasing errors. That's where the "three-to-one" rule comes in. The mics should be three times the distance apart compared to the mic to instrument distance. For example, if you are recording two trumpets and the mics are one foot from the trumpets, you should have the instruments at least three feet apart to avoid the mics picking up too much sound from the other trumpet.

[letrev]

if the mics are very close together, place them in an x-y pattern so they are not facing parallel.

Also, there are phase metering plug-ins you can use such as spectra-foo

http://www.mhlabs.com/products/spectrafoo.html

[Park Seward]

The X-Y 90 degree is for stereo recording. Like a Blumlein pair, it comprises two figure of 8 microphones, one on top of the other to make the capsules as coincident as possible, angled at 90 degrees to each other. Others are:
ORTF uses two cardioid microphones spaced by 17cm (roughly the same as ear spacing) and angled outwards at 110 degrees.
M&S uses two microphones, one facing forward (the Mid mic) and the other facing to the sides at right angles to the first mic (the Side mic). The Mid mic can be any polar pattern but the side mic must be a figure of 8. The output of the two mics is then fed into an M&S decoder. This converts M&S into standard left / right stereo by sum and differencing the raw M&S signals.

http://homepage.ntlworld.com/chris.burmajster/Mic.htm