In house-of-worship sound system installations, one of the biggest challenges is miking the choir.
We want to achieve a good balance, a natural sound, and high gain before feedback.
Another goal is to make sure that the microphones are invisible! It’s a tough assignment.
What mics work well for the choir? Where should the mics go, and how many are needed in each situation? The suggestions that follow should point you in the right direction..
Mics for Choir
The most popular type of choir mic is a small hanging mic. A few of these tiny microphones can be hung over the choir from the ceiling, from rafters, or on stands. They’re almost invisible when viewed from the congregation.
Choir mics are condenser types with a cardioid or supercardioid polar pattern. These patterns reject feedback yet have a wide enough pickup for good coverage of the singers.
Condenser mics can be made much smaller than dynamics of equivalent bass response.
An example of a miniature choir mic.
Choir mics are built in three parts: mic head, cable, and power module. The mic head puts out an unbalanced, medium impedance signal which travels through the long cable.
At the far end of the cable is a power module with an XLR connector or a terminal block. The module accepts phantom power and sends DC to an FET near the condenser mic capsule.
Also, the module equalizes the mic signal and converts it to low-Z balanced.
In some choir mics, the power module takes the form of a flat plate that is mounted in the ceiling. In other mics, the module is a tube with an XLR-type connector.
Mic Placement for Sound Reinforcement
When placing mics to pick up the choir, a critical factor is gain before feedback. To get enough gain, you must to mike the choir much closer than you would for recording.
Place the mics about 18 inches in front of the first row of singers, and about 18 inches above the head height of the back row (See Figure 1).
The mics are raised to prevent overly loud pickup of the front row, relative to the back row. The rows are equidistant from the raised mics, giving a well-balanced sound.
Figure 1: Typical choir mic placement (click to enlarge)
To achieve uniform coverage, use one microphone in the center of every 20-foot span of singers.
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A choir of 30 to 45 voices should need only two or three mics. Given a fixed miking distance, you’ll get less feedback with fewer microphones.
You might want to mount the choir mics on tall boom stands to experiment with placement during choir rehearsals. Once this is done, hang the mics permanently.
In miking a choir, it might seem important to consider the 3:1 rule. When multiple mics are mixed to the same channel, the distance between mics should be at least three times the mic-to-source distance.
This prevents phase interference between mics (comb filtering), which is a series of peaks and dips in the frequency response - a colored, hollow sound.
The 3:1 rule cannot be applied to miking a choir with a few mics. Why? Most of the singers are somewhere between the mics, and those singers will be picked up with some phase interference.
However, since each singer is in a different position relative to the mics, each singer is heard with a different coloration. The effect averages out over all the singers and so is not very audible.
Once the mics are placed, you need a way to hold them in position. Mic cables can lose their orientation as the mic cable uncoils over time, or the mics can swing back and forth in a breeze.
Some choir mics have a built-in hanger which comes with a tiny crossbar or pipe.
You thread a fish line through this pipe and attach the line to screw hooks in the side walls (See the example photo of a miniature choir mic above to view how this should look.). The guy wire keeps the mics oriented toward the choir.
If hanging mics is not an option, you might try making some clear plastic mic stands of Lexan corner molding. The stands can be cut to the desired height and mounted to or near the choir rail.
What if the choir is under a balcony? Try mounting some supercardioid boundary mics to the bottom surface of the balcony, near its front edge.
Other Considerations
Monitor loudspeakers can easily feed back into the choir mics. To keep feedback under control, try not to use monitors near the choir.
Instead, turn up the house loudspeakers. If the choir insists on monitor loudspeakers, don’t feed a monitor signal of the choir back to them because it will cause feedback with the choir mics. Rather, just feed them some music for accompaniment.
Part 1 of a multi-part fictionalized series on making it in the sound reinforcement business
I have a problem with the mics picking up the organ, which is blasting away a few feet behind the choir. Any organ in the mix sounds artificial, makes comb effects, and adds to the overloading of the music downstairs. Supercards with a null at the organ help. The choir director makes it sound “fine” upstairs, but what the congregation hears is way different. Sounds like they’re off in another room, and mumbling. But, feeding the choir into the main PA results in the voices emanating from the big line array down front, when actually the choir is in the loft in back. Sounds wierder with a soloist/cantor (where is she??) Solution: amping the choir mix into speakers on the edge of the loft, properly aimed to make it sound like the choir spatially, only a bit louder and much clearer (and in stereo). I set it up using parts from the old PA, and only 30 watts. Just adds enough “dry” into the sound to make it intelligible.