Sounds of the Sublime
Jan 1, 2001 12:00 PM,
By Bruce Bartlett
No venues require a wider variety of mic techniques than houses of worship. Sound sources range from live music, with instruments, organ and choir, to a variety of speech applications such as sermons, baptisms, altar rituals, weddings, bar mitzvahs and so on. Our challenges as installers are choosing the right mics and placing them carefully to pick up all of these sources well.
One goal of the sound system is to help the congregation hear more clearly. The message is important, so it must be loud enough and easy to understand. Another goal is to reproduce music with high fidelity or naturalness. And, of course, feedback must be under control.
To help you meet these goals, here are some tips on microphone techniques for houses of worship. The types of microphones you choose — and their placement — have a major effect on the sound quality. See both sidebars for brief reviews of microphone types, mic polar patterns and transducer types.
First, here are some general tips on microphone usage to reduce the likelihood of feedback.
- Use as few microphones as possible. Each time you double the number of open microphones, the gain before feedback drops by 3 dB.
- Turn down microphones not in use. This reduces the number of open mics, which prevents feedback and increases clarity. An automatic mixer (gated mixer) is a helpful tool here: it attenuates unused mics automatically.
- Keep loudspeakers and microphones as far apart as is practical.
- Keep microphones close to their sound sources — as close as possible, but no closer than necessary to achieve adequate volume before feedback occurs. Have the sound-system operator educate users to stay close to their microphones.
- Use directional mics. As shown in the sidebar, a microphone is directional if its polar pattern is cardioid, supercardioid or hypercardioid. (See Sidebar 2.)
SPECIFIC MIC TECHNIQUES
Each sound source requires a specific microphone treatment for the best effect. These suggestions are based on what has been most successful.
Worship Leader. The type of mic you will use on the worship leader depends on whether the person stays at the pulpit or wanders around. If they remain at the pulpit, install a lectern mic on the pulpit. This mic will also pick up anyone who walks up to the lectern to make an announcement or read a passage.
Modern lectern mics are slim and elegant. Their goosenecks make very little noise when adjusted. One mic company offers a lectern mic with a shock-mounted mic capsule and a ball-and-socket swivel mount that adjusts silently. Some models thread onto a 5/8-inch-27 Atlas flange, and the cable can exit downward or out the side.
One microphone at the pulpit gives a more consistent tone quality than two, so install only one. If you install two mics separated by a few inches, the sound path length from the mouth to each mic varies as the worship leader moves. When the signals of those two mics are mixed, the congregation hears a colored, filtered sound as a result of comb filtering. This is a series of peaks and dips in the response caused by acoustic phase cancellations. Prevent this problem by using only one mic at the lectern.
Be sure to add a foam pop filter to prevent explosive breath sounds (pops). Some churches prefer not to use pop filters because they are easily stolen or damaged. Another way to reduce pops is to speak about 8 inches from the mic and over the microphone rather than into it.
If you don’t want to install the pulpit mic permanently, try mounting a handheld mic on a boom stand about 8ý away from the worship leader’s mouth. Put a foam pop filter on the microphone.
Yet another alternative is to place a unidirectional boundary mic on top of the pulpit, near the edge furthest from the talker. Be sure to keep the mic out of cavities, which can degrade the polar pattern and frequency response.
If the worship leader wanders, use a clip-on lavalier microphone, either with a mic cable or with a wireless transmitter worn on the belt. The receiver in the wireless system plugs into a mic or line input in the mixer. Attach the mic at chest height about 8 inches below the chin. Use the belt clip that comes with the microphone, or place the mic connector in the pocket to act as a cable strain relief.
A wireless lavalier microphone also works well for a storyteller on the steps of the platform. Install a fresh battery in the transmitter before each service, and have the sound operator tell the user to turn on the transmitter before speaking.
Lavalier mics come in omni and cardioid pickup patterns. If possible, try to use an omni lav because it has far less handling noise and clothing noise than a cardioid. That’s because the omni mic diaphragm is more tightly damped, so it responds less to mechanical vibrations. Also, the omni mic’s output level is more consistent when the user’s head turns. And the omni picks up less breath noise from the nose than the cardioid does.
Choir. If the choir is loud enough in the house of worship without amplification, you don’t need to mike the choir unless you want to pick them up for recording or broadcast.
For permanent installations, you can hang miniature mics over the choir. Several models are designed specifically for choir miking. They are almost invisible, sound natural, and are available in black and white finishes.
Use one microphone in the center of every 20 to 30 foot span. A choir of 30 to 45 voices should need only two or three mics. Again, the fewer the mics, the better the gain before feedback.
If the choir mics are used for sound reinforcement, place them close to the choir to minimize feedback: about 1.5 feet in front of the front row of singers, and about 1.5 feet above the head height of the back row. This placement tends to pick up all the rows of the choir about equally. A fishline can be strung between the side walls and the mics to keep them from turning.
Monitor feedback into choir mics is a serious problem because choir mics are far from their sound source. Ideally, the acoustics of the sanctuary are designed so that the choir members can hear themselves without monitors. If the acoustics are not designed that way, try to keep the monitor level as low as possible. Some choirs use an in-ear monitor on each member!
If the choir mics are intended only for recording or broadcast, you can place them a few feet farther to pick up the acoustics of the sanctuary. If the choir is close-miked for reinforcement, but you want to record the service, add some digital reverb to the choir in the recording mix.
What if you can’t hang the mics? Attach them to stands using stand adapters. Use telescoping mic stands or photographic stands. Or create tall stands by threading each mic-stand tube to a boom arm: use 5/8-inch-27 female-to-female thread adapters.
Soloist or Reader. This person can be covered with a stand-mounted handheld microphone. Be sure to place a foam pop filter on the mic to prevent breath pops. Use a baby boom on the mic stand to reach a person seated in a presider’s chair.
A vocalist might prefer a wireless mic in order to move freely on stage. Although wireless mics are susceptible to interference from multipath, lighting dimmers, fluorescent lights and auto ignitions, this interference is minimal if you use a dual-diversity VHF high-band or UHF system.
Vocal Duo or Trio. One handheld mic on a stand, 1 to 2 feet in front of the center of the group. Or use one mic per person if feedback is a problem.
Wedding. Try a lavalier mic, as shown in Figure 3, on the worship leader. It will pick up the leader, bride and groom.
Altar Table. Place a unidirectional boundary mic on the table aiming at the people speaking. Some mic models are available in white to blend with a white tablecloth.
Baptismal. Hang a miniature choir mic overhead. If the baptismal is shallow, you can use a wireless lavalier mic because it eliminates the electrical hazard of dropping a microphone into the water. The wireless mic uses only a 9-volt battery and poses no risk of shock.
Organ. You probably won’t need to mike the organ for sound reinforcement, but you might need to for recording or broadcast. Omni condenser mics are recommended because they reproduce the low notes with richness and depth. Hang one or two mics 10 to 20 feet from the organ pipes or organ loudspeaker, 3 feet apart for stereo. Use one microphone for each group of pipes. Note that spaced microphones tend to give vague stereo imaging. If sharp imaging is important, use a coincident, near-coincident or mid-side array 10 to 20 feet from the pipes.
Congregation. You need to mike the congregation only for recording or broadcast. To do it, hang a cardioid microphone or choir mic several feet over the front row of the congregation, aiming at the back row. If the recording or broadcast is in stereo, use two microphones in a stereo arrangement, or place an omni boundary mic on each side wall.
Plays. If budget permits, give the lead actors wireless mini-mics, either head-worn or lavalier. For area pickup, place two uni boundary mics on the floor in front of the actors. Spread the mics a few feet apart so they pick up all the actors equally well. Mute all the other mics in the system to prevent feedback.
Typically, children’s voices are too quiet to pick up with a distant microphone. If wireless mics can’t be used, place a handheld mic or two on stage. Have the children say their lines close to the microphones. You’ll need to instruct the sound-system operator about this.
Musical Instruments. Mic techniques for instruments is a subject in itself. Check out the many books on miking, or order some mic application guides offered free by several mic companies. In this article we’ll cover only the acoustic guitar and piano. Although the sound-system operator does the miking rather than the contractor, you should know what mics the operator is likely to need.
If the guitarist has an electrical pickup on the guitar, its cable probably has a phone plug on the end. Connect this phone plug to a direct box, and connect the direct box to a mic input. Set the ground-lift switch on the direct box to the position where you monitor the least hum.
If you want to mike an acoustic guitar, there are several ways. One is to tape a miniature omni mic onto the guitar body, halfway between the sound hole and the bridge, near the low E string. Another way is to mount a uni condenser mic on a boom stand and place the mic near the twelfth fret.
The main source of feedback with the guitar mic is the floor monitor. So feed the pickup 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.
To mike a grand piano, tape two omni boundary mics to the underside of the raised lid, one over the treble strings and one over the bass strings. Put the bass mic near the tail of the piano to equalize the miking distances to the hammers. If feedback is a problem, close the lid and adjust the mixer EQ until the sound is natural. Usually a cut around 300 Hz is needed. Another option is to place two cardioid condensers about 8 inches horizontally from the hammers, 8 inches above the strings, over the bass and treble strings or use a stereo mic pair in the middle (position C).
An upright piano can be miked with two cardioid mics near the sound board, or aiming at the open front.
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 installation will provide a clear, natural sound that enhances the worship experience.
Bruce Bartlett is a microphone engineer, recording engineer and audio journalist. His latest book is On-Location Recording Techniques published by Focal Press.
basic microphone types
Listed below are some of the forms of microphones used in houses of worship:
- Miniature clip-on mics (lavalier mics), which clip onto the worship leader’s robe or onto musical instruments.
- Lectern mics, which mount on the pulpit or lectern.
- Miniature choir mics, which hang over the choir.
- Handheld mics for vocalists.
- “Stick-shaped” dynamic and condenser mics for musical instruments.
- Surface-mounted mics (boundary mics), which are put on surfaces (floor, ceiling, walls, tables). Models are available with omni or unidirectional pickup patterns. The omni type is actually hemispherical, and the uni type is half-cardioid or half-supercardioid.
Several mic companies offer microphones for each of these needs. Many of the mics are so small they become nearly invisible in use and so do not distract from the service.
a Microphone primer
Microphones are 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 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.
Microphones also differ in the way they convert sound to electricity. A condenser or electret condenser microphone has a thin diaphragm mounted one- or two-thousandths of an inch from a metallic disk called a backplate. The diaphragm and backplate are charged with static electricity — a DC voltage — forming a capacitor. In a true condenser or external bias mic, the voltage is supplied by a circuit in the mic electronics. In an electret condenser mic, the voltage is produced by an electret material in the diaphragm or on the backplate. Sound waves vibrate the diaphragm, which varies the spacing between diaphragm and backplate. In turn, this varies the capacitance, which generates a signal analogous to the incoming sound wave.
In a dynamic or moving-coil microphone, a coil of wire attached to the diaphragm is mounted in the gap between two magnetic poles. When sound waves vibrate the coil, its conductors cut the magnetic lines of force, generating a signal.
Generally, the condenser type is higher quality, but requires a power supply, such as an internal battery or an external phantom power supply, to operate. This supply is already built into some mixers. Another advantage of the condenser type is that it can be miniaturized. A miniature condenser mic is desired when you want the mic to be invisible — say, hanging over the choir, clipped onto the worship leader’s robe or affixed to the pulpit. Dynamic mics are rugged and can handle high SPLs without distortion.