Sound Advice: Stereo Recording Techniques (page 2)

This method, also called X-Y Stereo or "coincident," uses a matched pair of cardioid (unidirectional) microphones. The microphones are positioned 90 degrees opposite of each other with one microphone above the other and the diaphragms vertically aligned . This assembly mounts on a tall mike stand and raised above the recording subject, similar to the A-B stereo method above. Again, position is critical for the best recording, but the same real-world factors apply. The further back your mike stand is positioned, the more distant the sound will become. This can actually be a benefit in a smaller or acoustically "dead" room. Put on the headphones and let your ears guide you.

Although the stereo image from this arrangement is not as strong or detailed as the previous method, it is still very good, and mono compatibility is near perfect. The X-Y stereo method is a favorite in the broadcast industry for its clear playback on any audio system, whether it is mono or stereo.

The video world is full of acronyms. This one stands for Office de Radio et Television Française, the French equivalent of the FCC. Also called "near-coincident" this recording technique is very similar to the X-Y method above, with one small difference. Instead of placing the microphone diaphragms directly over each other, the ORTF technique locates the diaphragms 17cm (about 7 inches) apart, at a 110-degree angle . This spacing more accurately represent the spacing and directional characteristics of our ears.

The ORTF technique is a great compromise. It retains a great deal of stereo information while maintaining good mono compatibility. This is important when you want maximum sound detail while producing a video that will sound great on any home system.

This unique method uses two different microphones - one cardioid (unidirectional) and one figure-8 (bi-directional). The cardioid mike is mounted to face the recording subject while the bi-directional mike is mounted with its directional faces pointing side-to-side . The microphone elements may be separate or enclosed in the same body.

Due to its "single point" setup, M-S microphones yield perfect mono compatibility yet retain the ability to provide spacious stereo content as well. To record M-S audio to your tape, you'll need a matrixing transformer. This mixes the two signals and allows you to control the width of the stereo picture. You may have a hard time monitoring the audio in the field, as you'll have to "un-matrix" the audio on playback. Several manufacturers provide switches to blend the microphones in the field and record standard left-right audio to your tape.

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