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How should I stereo-mike a choir at a distance for recording?
I have been asked to record a 40-member choir, soloists, and pipe organ in a live performance in a large (100' ceiling) church. I originally planned to use the CM-700MP in an ORTF setup [mics angled 110 degrees apart and spaced 7 inches apart horizontally]. The mic pair was to be about 4-5 meters from the choir in the front of the church. I have now been told that the choir will be in the back balcony at the organ console, and due to space constraints, they will be flush up against the front of the balcony, which is around 30' up. The microphones must be placed at the break in the middle of the church, approximately 80-90' from the choir.
My question is, given the distance from the sound source, would the ORTF prescribed angle of 110 degrees still be correct? At that distance, the microphones will not be directed at the choir. Would a smaller angle be more appropriate, or at that distance is the sound so lacking in directionality that it would not make a difference? Does the 110 degree angle hold true regardless of the distance? Also, should I angle the microphones up to direct them at the choir?
Reply: Yes, angle the mics upward to aim at the choir. This is done so that the choir will be more on-axis to the microphones.
You have a few stereo miking options, depending on your desired results:
1. A distant choir fills a narrow angle visually, and you might want to keep that effect in your recording. If so, leave the mics in the standard ORTF configuration. The room reverberation will still spread between the playback loudspeakers.
2. If you want to make the choir sound closer or clearer (to compensate for the unusually high miking distance), aim the two CM-700s straight at the choir and place them about 2 to 4 feet apart. This spaced-pair method gives less sharp imaging than the ORTF method. But the clearer sound (higher direct/reflected ratio) that results may be worth it. Use as tall a mic stand as you can find. Is it possible to hang the mics closer to the choir?
3. If you want the choir to appear as wide as the distance between speakers while using the 110-degree ORTF angle, increase the spacing between mics while keeping the mic angle constant. You could increase the angle instead, but that would place the choir too far off-axis of the microphones.
Whether you choose method 2 or 3, you will need to adjust the mic spacing or angling to get the desired stereo spread. You might want to make a trial recording when the choir is absent, as follows: Set up a particular mic spacing and/or angling and record yourself describing the mic setup. Then record someone who is standing in the center of the choir area. Have them move to the side while announcing their position: "center, half-left, far-left." (The far-left position is where the far-left side of the choir will be.) Try several combinations of angling and spacing, like 0 degrees/2 feet, 0 degrees/4 feet, 110 degrees/7 inches, 110 degrees/14 inches. Play back the recording over two speakers and listen to determine which method worked best.