Phasing Issues With Multiple Microphones - M-Audio Microphone User Manual

common acoustic damping materials for home studio use. Music stands can also be reflective
something you can compensate for by simply draping towels over them.
While a reasonable amount of absorption is often desirable for isolation, too much damping can
create an anechoic space that literally sucks the life out of a recording. In more permanent project
studios, consider creating a flexible acoustic environment. One solution is a series of gobos or
movable panels with a reflective surface on one side and an absorptive surface on the other.These
can then be moved and placed as desired for a given project. Another solution is to create
reflective walls with movable absorptive drapes in front of them.
Finally, don t overlook the acoustic resources you have available. Many a vocal track has been recorded by running
a mic into a tile or marble bathroom. (People like singing in the shower for good reason the sonic reflectivity
can make even mediocre voices sound great!) Recording engineers have frequently placed speakers and mics in
concrete stair wells to transform the concrete acoustics into reverb chambers. The drum track for Led
Zeppelin s classic When the Levy Breaks was so incredibly ambient because John Bonham s drums were set up
in the stairwell of a stone castle. Similarly, some classic Jimmy Page tracks were realized by placing the guitar amp
in a fireplace and miking the top of the chimney. Again, the only real rule is to use what works for the track.

Phasing Issues with Multiple Microphones

The use of two microphones can introduce problems owing to phase discrepancies between the
mics and that potential increases with the number of microphones in concurrent use. In essence,
phasing problems occur when a sound reaches different mics at different times. Telltale signs are
different notes from the same source sounding at different volumes, or bass response that is overly
strong or overly shallow.
Here are a few tips in minimizing phasing problems when using multiple mics:
Move the mics. The first line of defense is to just get into the studio with headphones on and
move one or more of the problem mics until the phasing issue is resolved.
Check the cables. If a cable is accidentally wired out of phase, it can cancel out the signal from
a neighboring mic. Make certain that the mic cables are wired with continuity (i.e. pin 1 on one end
goes to pin 1 on the other end, and so forth).
Apply the 3:1 Rule. If possible, microphones should be
three times further away from each other than from the
source. As an example, microphones placed 5 inches away
from a sound source should be at least 15 inches apart
from each other. (This does not apply to the coincident
stereo miking techniques we ll discuss shortly.)
3x
1x
1x
Minimize the number of microphones in
concurrent use. The more open mics you have, the
greater the potential for phasing issues. While it might be
tempting to put a separate mic on each component of a Placing two microphones three times the distance
from each other as they are to the sound source
drum kit, for example, the tradeoff is the amount of time
can eliminate phasing problems
it might take to eliminate phasing complexities. Less can be
more in situations where you have difficulty getting phasing
under control.
Separate the sound sources. With the exception of stereo recording, the general idea behind
using multiple microphones is to isolate the sound sources. Phasing issues provide another reason
to isolate the sources. Solutions include simply spreading the mics apart, putting them in separate
rooms or isolation areas, or using baffles, gobos and the like to provide additional separation. In the
case of two mics on the same instrument, it is sometimes beneficial to devise a baffle that goes
between the mics.
18
Choosing & Using Microphones