Lavalier microphones offer a convenient method of recording speech with a high degree of audio quality. They’re used extensively in TV news and public affairs programs to mike people sitting or standing still.
Lavalier microphones are visible onscreen, appearing as tie clips, maing them inappropriate for dramatic work. Lavalier mikes also tend to produce a lot of noise on people who move. But if you need to record talking heads, the lavalier is the ideal choice.
The lavalier mikes of the 1950s were rather large cylindrical objects attached to a rope and worn necklace-style. With microphone miniaturization technology it became possible to fit smaller lavalier mikes onto spring-loaded clips. This is the form we see today.
Most modem lavalier mikes feature a condenser-type sound pickup element. Condenser microphones work on the principle of varying electrical capacitance. They require external power from a built-in battery or other power supply.
Many camcorders offer a small jack labelled “plug in power” or “mike power” that can be used with an external condenser mike. Be sure the camcorder voltage and pin configurations match the mike and its plug.
Most videomakers prefer to use microphones with built-in batteries, plugging in mikes from a wide variety of manufacturers.
Many miniature lavaliers are single-piece units with a small mercury button battery in the middle of the mike tube.
The smallest, professional-quality sub-miniature lavaliers are two-piece units. The mike element is mounted in a tiny cylinder, attached by a thin cable to a larger tube housing the battery and amplifier circuitry. Only the tiny mike element is visible on camera, the battery/ amplifier unit is tucked in a pocket or clipped to a belt.
On professional lavalier mikes a thick three-wire balanced XLR microphone cable attaches to the amplifier, allowing for long cable runs with minimal degradation.
Lavalier mikes are designed to accentuate voice-range frequencies, heightening intelligibility and sense of presence. They usually offer a directional pickup pattern, making the mike less sensitive to sounds to the side or behind. Omnidirectional models are also available.
Two problems can arise when you clip lavalier mikes to people: off-axis tonal response, and clothes-scraping abrasive noise.
Off-axis response occurs when a microphone with a directional pickup pattern points in the wrong direction. When the mike dangles from a man’s collar, pointing towards the camcorder, it will still pick up his voice. But the sound will be weak, noisy and tinny.
Lest positioning involves pointing the mike up towards the chest cavity to pick up a mixture of the deep, resonant sound from the chest and the crisp sound emanating from the mouth, If you point the microphone in towards the chest, sound will be muffled. If you pin the mike near the neck the sound will come across tinny, lacking bass.
Men wearing neckties can use the mike as a tie clip, running the cable behind the tie or inside the shirt. For somebody in a button-down shirt, clip the mike to the shirt’s center edge.
Before clipping the mike, make sure the talent assumes recording posmre. If the subject shifts positions, or opens the jacket, the mike position may change drastically.
People clad in t-shirts or sweatsuits can pose problems. You may be able to hook to the collar, as long as the mike doesn’t press against the throat.
If a pocket is available, clip along the top edge, with the microphone hanging below. The best audio results present a visual horror: fold an inch of the shirt near the middle, and clip on the mike.
Noise created by clothes brushing up against the microphone is a common problem. When you attach a mike, make sure it rests on top of all clothing. Don’t place the mike on the inside of a jacket or shirt unless shooting drama with an absolute need to conceal.
When shooting outdoors a windscreen should be used to prevent the thrashing noise that occurs when the wind blasts the mike’s sensitive diaphragm.
The best lavalier windscreens are made by professional microphone manufacturers. You can improvise a somewhat less effective alternative using the foam earpads sold as replacement covers for Walkman-type headphones.
The wiring requirements encountered when using a lavalier mike with a camcorder can be tricky. The cable length needed can be quite extensive, even when the subject is but a few feet from the camcorder; all that slipping through clothing and tucking behind chairs.
Balanced lines can reduce the amount of hum and noise picked up by long microphone cables. Unfortunately, most of the less-expensive lavalier mikes use a two-wire unbalanced system; nearly every miniplug micro-phone is unbalanced.
Be cautious about running miniplug extension cables. Adding just six more feet to a six foot cable can noticeably increase the static and hum.
For best results, use a matching transformer to convert the unbalanced miniplug connection to a three-wire XLR plug connection. Then use a professional XLR-to-XLR mike cable for a run of twenty feet or more; use another transformer to convert the XLR back to the unbalanced miniplug camcorder mikejack.
A wireless mike offers freedom from such worries. At present there are no transmitters small enough to fit in a lapel mike. Instead, a small tiepin lavalier mike is tethered to a larger transmitter unit that can be slipped into a pocket or clipped onto a belt.
Since the cable runs from the mike to the transmitter and from the receiver to the camcorder are each quite short, the noise pickup problem is kept to a minimum, even with unbalanced miniplug connections.
To determine whether a mike is positioned properly and correctly connected you must listen to the audio signal. Wearing headphones during the shoot will alert you to clothing noise, dying batteries and other problems that can arise long after the sound check.
If you listen carefully and set up the lavalier mike in a good position, you can achieve results noticeably superior to those achieved with a camcorder microphone.
An accessory mike involves some additional effort, and only you can decide which projects might merit it. Those involved in serious video work should have one available always.
Cliff Roth is a Videomaker contributing editor.