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.)

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 drum kit, for example, the tradeoff is the amount of time it might take to eliminate phasing complexities. Less can be more in situations where you have difficulty getting phasing under control.

3x 1x 1x

Placing two microphones three times the distance from each other as they are to the sound source can eliminate phasing problems

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.

Choosing & Using Microphones

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M-Audio manual Phasing Issues with Multiple Microphones