One of the biggest challenges in church sound 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..
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.
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.
An example of a miniature choir mic.
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 mic 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 (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.
To achieve uniform coverage, use one microphone in the center of every 20-foot span of singers. A choir of 30 to 45 voices should need only two or three mics. Given a fixed micing 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.
Figure 1: Typical choir mic placement (click to enlarge)
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 micing 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.