How to Record in True Stereo
Years ago I used to work on a popular law enforcement reality show where we followed police as they served and protected us. Although there was a separate sound man and cameraman with a microphone each, and the show advised that it was shot in stereo, the soundtrack rarely delivered it, because stereo is more than having two audio tracks. True stereo is reproducing the illusion of three dimensionality through recording. If the source of sound is on the right side of the screen, it seems to come from there, not from where the source happens to be relative to the sound man. Here's how to achieve true stereo in your recordings.
- Difficulty:
- Moderate
Instructions
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You do need a minimum of two discrete audio channels and two microphones. Most music recordings use far more, but it's impossible to record stereo without at least two sources, maintained separately through the entire recording and reproduction process. Some mini DV camcorders have stereo microphones. They are a good compromise and can deliver acceptable results, but there is always a tug of war between the best place to shoot and image and the best place to mic it. On board stereo camera mics are a compromise. To achieve the best results, you should use external mics.
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If your recording device has two external mic inputs, hook up is simple. Choose mics of the same design, type, ideally of the same model and feed each into a different input. However some external stereo inputs, mainly for camcorders can be confusing. You might find a single 1/8" mini stereo phone jack which is often used just for high end mono microphones. Double check to make sure that you are actually recording on separate channels. If you are, the plug is configured as follows. The tip and ring of the plug conduct separate audio signals while the shield is common to both. It is possible to buy a Y splitter for individual microphones that will feed into this jack.
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Next decide on microphone configuration. For this posting, I'll focus on those you can achieve with just two identical mics of the same model. There are more sophisticated options that pros use. In all these cases you'll need mic stands for each microphone.
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There are two options with omnidirectional microphones which pick up sounds equally from all angles. The first is spaced pair micing. It's intuitive and is probably the first set up that most people try. It simply reproduces the loud speaker spacing with microphones, set apart at 7 to 10 feet from each other pointed at your audio source. Unfortunately, this set up does not provide the best sound localization. A baffled omni pair means separating two omni microphones a foot apart separated by a baffle like a foam wig head. This method is an improvement, because in some respects, it's the reverse of what head phones do.
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Cardioid mics are directional, reproducing sounds more strongly in the center. These are the preferred mics for most field production. There are two basic set ups here. Coincident pair, also called the X / Y method involves centering a pair of cardioid mics before your audio source, pointing them at each other with one slightly above the other. Near coincident pair, means center and cross an identical pair of mics away from each other at about 110 degrees. The greater the angle, the greater the stereo separation, so adjust the angle so that the sound doesn't appear hollow in the middle.
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Be sure to monitor with good flat response stereo headphones. Although I frequently use ear buds when I am shooting news style, you'll hear far better with headphones that fully cover the ears.
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Tips & Warnings
Keep your mic input and placement consistent through the recording process or your sonic image will flip sides.
Beware of the effects of phase cancellation. Double check that your microphones are wired the same way. If you can, feed both signals into a mono monitor like a speaker. If your set up is off and the audio signals reach your mics 180 degrees out of phase, you could have some sounds that will actually cancel each other out if played back in mono. Remember, not everybody will be playing your audio back through a high end system. The last thing you want is to put a VHS tape together for your own mom of your child's first words only to have them rendered unintelligible due to a difference in audio phase.
