Nothing can disrupt a worship service like the annoying squeal of feedback from the sound system. Feedback is a ringing sound or squeal which occurs when the signal generated by the microphone is reproduced by a nearby loudspeaker which is then picked up by the microphone and the re-produced by the loudspeaker and picked up by the microphone again, etc. This looping process will continue until the microphone is relocated so that it does not pick up the sound from the loudspeaker. Feedback can be very specific to frequency and /or location. There are a variety of outboard processors that minimize feedback problems, but much can be gained by the proper selection and application of microphones in Worship.
For the most part, microphones can be classified by how they convert sound energy to an electrical signal. The most common types are condenser and dynamic. In a place of worship, condenser microphones offer a number of advantages over dynamics. First, condenser microphones can be made much smaller (and less conspicuous) than dynamics without sacrificing performance. They also have higher sensitivity for excellent pickup, even at the distances required by hanging choir mics. They have lower handling noise than dynamics, and their extended frequency response provides a crisper, more accurate reproduction of sound. Finally, condenser mics have superior "transient response" for accurately reproducing sudden sonic impulses, such as those produced by voice, piano and percussion. Condenser microphones require a power source for their internal electronics. Some models can receive power from an internal battery while others may be "phantom" or "remote" powered.
Microphones are also classified according to the way they pick up sounds from different directions. An omnidirectional (omni) mic picks up sound equally well from all around. A unidirectional (uni) mic picks up mainly what is directly in front of it. The most common type of unidirectional mic is the cardioid type. It has a broad angle of pickup in the front, and rejects sounds from behind the mic. Supercardioid is a tighter pattern, but with more pickup from the rear than cardioid. Hypercardioid is tighter still, with even more pickup from the rear. Because they reject feedback, room reverb and leakage, unidirectional mics are the most common choice for sound reinforcement.
Both VHF and UHF frequency bands are shared with a large number of other devices including TV stations, communications equipment and a large number of wireless microphone systems. Because of this sharing there is the possibility that someone else (anotherchurch) in the area may be using the same frequency. You should not use two microphones with the same frequency. This will result in interference and render the system useless. Manufacturers often sell a wireless handheld and lavaliere or instrument microphone package. Although these systems are designed for individual users, they are not intended to be used simultaneously. Each mic can be used with the same receiver, however they cannot operate at the same time.
Wireless microphones are usually sold with one or two antennas. Dual antenna or "diversity" systems are able to avoid dropouts because they have two antennas and two receiver channels. Because the chances that there will be simultaneous dropouts at both antennas are extremely low, diversity receivers provide almost complete immunity from dropouts. Diversity wireless systems will almost always have better operating range than similar non-diversity systems.
For stage vocals use a dynamic handheld cardioid mic, such as the Shure SM-58. Every church should have an adequate stock of this workhorse microphone, as they can be used in place of most microphones when failures occur or when you have expanded needs. If budgets allow, try using a condenser cardioid like the Shure SM-87. Higher quality microphones will always produce better results in your mix and on stage.
When micing a piano try using a stereo pair of cardioid mics (preferably condenser, like the Sennheiser ME-40) aimed inside the piano at half-stick or full-stick open. If your church has an upright piano, open the top lid and aim two condensers in, or, alternatively, point two condensers at the back sounding board of the piano. If your worship team uses a keyboard, invest in a high quality direct box to convert the signal from unbalanced ¼" to balanced XLR inputs and run directly into the console.
There are a number of high qualities microphone "kits" specifically designed for micing drums and percussion. If you don't have the resources to buy a complete drum mic "kit", you should at least invest in a dynamic mica such as the AKG D112 for use on the kick drum. You can easily substitute a Shure SM-57 on the snare and employ two condensers or some more SM-57 microphones in an overhead configuration to pick up the toms and cymbals.
Acoustic guitars, like all acoustic instruments, have the ability to change the timbre accordingto the recording axis and the position of the microphone. Most often you will use the direct output of the acoustic guitar coupled to a DI Box for interfacing to the console. Remember to set the ground-lift switch on the direct box to the position where you monitor the least hum. Again here is where the quality of the direct box you select will make a huge difference in the results. On those occasions when you can mic the acoustic guitar use a cardiod condenser microphone. Begin by adjusting the height of the microphone stand to the mid of the guitar strings. Position the microphone close to the front body of the guitar and near the twelfth fret to get the best results. Changing the mic position proximity and angle will affect the low frequency response.
A hint when feedback from any guitar is a problem or you are constantly adjusting the eq to keep things correct: Feed the pickup or direct out to the monitors, and feed the mic signal to the house speakers. That way you get minimal feedback from the monitors and natural sound in the house.
Some general tips on microphone usage to reduce the likelihood of feedback.
In conclusion, houses of worship require a wide range of mic choices and placements. Each sound source has special miking needs. But with some attention to those details, your application will provide a clear, natural sound that enhances the worship experience.