Using the Mic: Performance Perspectives by Tom LeFevre tlefevre@soundandsong.com

Whether we are actively involved in ministry as singers, players, preachers, or readers of the Word, we are the Lord's instruments. One of our most important tools in effective sharing of our offerings is the microphone. With or without a major mixing/amplification footprint, and a skilled sound mixing operator, every presenter in service needs to use the mic as astutely as possible. Understanding a few basic principles can help to avoid many common mistakes.

Quick Review of Mic Types

Even among people who have performed extensively, confusion surfaces over types of mics, pickup patterns, impedance, etc. The most common mic used in churches and live music situations is the dynamic type. This tends to be the most cost-effective mic for most singing and speaking purposes. It is also the most rugged. It is so named because sound causes a small coil of wire to move back-and-forth in a permanent magnetic field. This is the same principle as a generator/alternator or an electric motor (in reverse). This dynamic motion creates a small electric current which is then amplified. Important to know is that the dynamic mic generates its own current and requires no batteries or "phantom power" coming from the mixer via the mic cable. Mics that require batteries present a support logistic that needs attention. Dynamic mics can survive the most "knocks" for typical praise team packing and unpacking. Their frequency response and overall sound reproduction fidelity is adequate for most vocal and many musical instrument applications.

Another mic used for musical and speech applications is the condenser mic. This type generates a much smaller electrical signal in its sound sensor - which is an electrical capacitor, or condenser. Its signal generation involves motion of much smaller mass than in the dynamic - but it requires a power boost. That comes from a battery (a dead one won't help), or via the mic cable attached to your mixer. This is called "phantom" or indirect power, if no batteries are involved. Whenever possible, avoid applications requiring batteries. Wireless applications will require them, but experience shows that a large church with a lot of wireless mics will need a very thorough and 100% consistent battery testing and replacement function. Let's not even think of the term "battery ministry". Condenser mics usually have a greater sensitivity than dynamics, but they also cost more, and are less rugged. Often condensers are preferred for picking up musical instruments like a classic guitar, string quartet, or harp. A special type of condenser mic is a flat mic that specializes in picking up sound in the zone of reflection just barely above a surface. This is called the "sound pressure zone" and such mics (like those made by Crown and Audio Technica) are very effective in miking grand pianos, by being mounted under the lid. In general, due to lower mass of their pickup type, condenser mics are better for percussive instruments that make sharp transient sonic attacks: pianos, drums, plucked violins, classical guitars, etc.

Regardless of type, no mic made will compensate for a player or singer that's not quite on the right pitch. The point is that any mic is only a link in the chain of good sound and music. All the links have to be strong if the chain's going to pull the weight our missions require.

Pickup Patterns

Not to be confused with mic types, are patterns of sound pickup sensitivity. A mic that picks up sound with equal sensitivity in all directions (Think of a sphere in three dimensions.) is omnidirectional. Most all wireless lavalier mics are this type. Omni's are the most prone to feedback loop between mic and speaker, because of this sensitivity. For this sole reason, it's especially important for preachers and dramatists using lavaliers, that they attach their mics in the center axis of their body, about 5 to 6 inches below their chin. The farther away from the speaker's mouth, the higher the gain sensitivity must be on the mixer to ensure the congregation will hear. With omni's, a much smaller margin of gain before feedback exists. So help preserve the sanity of the sound ministry and keep the lavaliers centered close to the voice - not on one side jacket lapel or halfway to the waist. Also, be mindful of clothing and body motion, as this sound will also be picked up.

The basic singer's mic is the unidirectional (most sensitive in one direction, and therefore a better tool for preventing feedback loops). Uni's come in three sub-types of focus, or breadth of pickup pattern. Broadest is the cardioid, or 3-dimensional heart-shaped pickup sensitivity pattern. The cardioid can effectively pick up singing up to about 65 degrees off its center axis. So it's a good mic for up to two singers to share at close range (about 4 to 6 inches, as long as they're friends and/or have good dental hygiene). The supercardioid is a more focused sensitivity, effectively picking up sound up to about 55 degrees off axis. Last, the hypercardioid is the most focused, with an off-axis pickup angle effective up to about 50 degrees. The cardioid completely ignores sound from directly behind, while each of the super- and hypercardioid pick up some sound from the backside of the mic. Because of the cardioid's total rejection of sound from behind, it's the best pattern to use in conjunction with one or more floor monitors placed near singers. Remember - the pickup pattern has nothing to do with the mic type. Both dynamic and condenser mics can be manufactured to be sensitive in any of these patterns.

A Word About Impedance

All mics have an electrical characteristic called "impedance". Think of this as resistance to passage of electric current. It's important to note that while most electric instruments have high impedance characteristics, almost all mics have low impedance attributes. High impedance signals - like that from an electric guitar or synth-keyboard - can only travel effectively for about 20 feet. These signals are also susceptible to radio-frequency interference ("RFI", like from a neon light), and need to be transformed into a low impedance signal through a "direct box" junction transformer, on their way to a mixer 50 to 100 feet away. Low impedance lines are called "balanced" and have 3-pin XLR type connectors. They are far less vulnerable to RFI, and can carry mic signal for hundreds of feet.

Miking a Choir

Most effective for this purpose are cardioid hanging-style mics. These are available in black or white, typically, to minimize obviousness in contrast against background color. A rule of thumb is to use one mic for every 20 to 25 feet the choir is wide. Center them in front of the section to be miked. position them vertically a foot or two higher than the tallest back row singer, and aim them at the back row voices. Hang them so they're about 2 to 3 feet in front of the first choir row of singers. Trying to pick up a choir with too many mics results in excessive overlapping of pickup pattern, resulting in sound wave phase cancellation. The result can be a hollow sound in various frequencies.

Tips for the Praise Team

Be sure all singers grasp the concept of feedback, and know where they're most likely to encounter it. Most mics have on/off switches. Brief all singers on how to turn theirs on and off. Sounds simple, but in a feedback emergency it can be invaluable. Never point a unidirectional mic at a monitor. It can happen to experienced people when they're not paying attention.

Some teams hold their mics while others lead singing worship with the mic in a stand. A wireless mic, too, can remain in its stand. Either way has plusses and minuses. Like inexperienced actors, praise singers often just "don't know what to do with their hands". When you pick up a mic, you have visual mobility. You also introduce more cord-motion noise. Whenever a cord is jarred, some vibration is carried to the mic via the cord. Either way, it's most important to sing in a consistent close proximity to the mic. Three to four inches is a good rule of thumb for a soloist. That gives some leeway to get closer to compensate for very soft passages (like a presence effect on a long falsetto note). A big advantage to working from a stand is that two hands are free for invitational gestures to the congregation, or for clapping hands. Better yet, to play a shaker, tambourine, cabasa, or conga. It's not only visually interesting in rhythmic songs, but these percussive touches can greatly enhance the song's feel and color.

At that distance also, the speaker or singer can anticipate the coming of breath "pops" and surges on certain consonants - especially "p", but also "b" and hard "t". Most mics have built-in pop filters. Special foam or more sophisticated filters can be obtained. But singers and speakers can also learn to anticipate "p's". If singers hold the mic a slight angle to the side, a breath burst on any letter won't blast directly into the mic. There will still be plenty of pickup sensitivity to get the music.

Miking Electric Instruments

It's common in some situations to take a direct signal from a guitar or synthesizer and route it to the mixer. While this can minimize the "bleedover" effect from amplifiers, it bypasses many of the special coloration effects that modern amps can add to the color of a guitar or bass. These colorations - phase, chorus, envelope filters - are a big interest factor in contemporary music. These same amps often provide balanced low-impedance outputs that can plug right into the mixer. It's still valid to place a mic about 8 to 10 inches from a guitar speaker, off-axis slightly. Drums sound best if miked by condenser, except for the kick-bass, where a special high sound pressure level dynamic mike is best. Isolating the set with a Plexiglas screen usually allows better mixing for the overall sanctuary space.

As said earlier, mics are a critical piece of the puzzle, and the most expensive mic in the world won't make up for a wrong note, insufficient rehearsal, or a sound person asleep at the wheel. But knowing your tools will make you and your team more confidant in whichever part of sound ministry and worship you have come forth to share your gifts.

 

Reference: Yamaha Guide to Sound Systems for Worship; Edited by Jon Eiche; Hal Leonard Publ.