Making mics last
Our journalistic hero, caught in a bind on location, needs to pound a nail. No hammer in sight, he pulls out his trusty handheld interview mic (complete with station ID flag) and, like “MacGyver,” quickly seats the offending nail, just in time to complete the interview and boost station ratings. We have all heard these stories, and although some microphones are fairly rugged, we would stop short of using one as a hammer.
In reality, a microphone is a precision instrument that, with a little care, can last many years. Today, broadcasters use many different types of microphones. Two of the most popular are dynamic and condenser.
Dynamic microphones are a prevalent choice for handheld interviews, live vocals and some air studio uses. Characterized by their large physical shape, these inherently rugged microphones will take most of the abuse a field correspondent can dish out. The biggest issue with dynamic handheld mics seems to be with headcase grilles getting clogged and damaged. Simply removing the headcase, cleaning out the debris and replacing it can improve performance. Plus there's the hygiene factor: Cleaning the grille can help prevent the spread of germs. An external foam windscreen is also useful for protecting the headcase.
Don't overlook the microphone's connector. Over time, the connector insert may come loose with repeated use. Simply tightening the small setscrew that that holds the connector in place will do the trick. Because the threads in the insert are reversed, turning the screw to the right actually backs it out of the connector insert, securing it to the microphone body. A technician's “greenie” screwdriver is ideal for this task.
Condenser microphones with their extended response, low handling noise and ability to be miniaturized are commonplace on set and location. A far cry from the neck-worn lav mics of the last century, the new breed of subminiature lavaliers are practically invisible on camera and can outperform the best dynamic mics. Although these microphones are quite rugged, a little common-sense care can extend their lives. Here are some tips to make them last longer.
When using wired lavalier microphones, attach the power supply/module to the wearer with the power supply's clip. This keeps the strain off the smaller lav cable should the wearer decide to get up and walk with the mic. Store the mic with its cable coiled in a protective case, and resist the temptation to coil the mic and cable around the radio-mic transmitter pack. When wearing a radio-mic transmitter, secure the mic cable under the transmitter belt clip to take strain off the connector.
Some lavalier microphones come with an accessory kit that includes small “makeup caps” designed to slip over the microphone capsule. These are used to keep theatrical makeup from clogging the small element opening and damaging the mic. They also work well to keep other debris out of the mic and can be easily removed for cleaning with rubbing alcohol and a cotton swab.
Remember the “broadcast loop” technique for dressing a lav mic cable on a clothing or tie clip. (See “The broadcast loop” sidebar below.) Besides helping to minimize the pickup of mechanical sound transmitted up the wire, this helps lessen cable strain on the mic.
All condenser microphones require power to operate. Typically, this power supplies energy to a small amplifier circuit inside the microphone, although some condenser microphones use it to put the electrical charge on the capsule's backplate. Depending on the situation, this power can come from a microphone's built-in battery or up the microphone cable in the form of phantom power provided by the mixer, camera or an outboard power supply.
Even though the batteries will last in excess of 1000 hours of operation, when using battery-powered mics, make certain the batteries are fresh, especially for that critical production.
For microphones that require it, verify that the phantom power is switched on. I have been on locations where time was spent troubleshooting bad mic cables, only to discover that the phantom power was turned off at the mixer. When turning phantom power off or on, and when connecting or disconnecting condenser microphones, turn the input channel's level down to avoid nasty “pops” in the audio system.
Because the backplate and diaphragm in a condenser mic are charged (think capacitor), condenser microphones are more susceptible to moisture than are dynamic mics. When used in situations with high humidity, there is a chance that excess moisture on the diaphragm may cause sizzling sounds similar to bacon frying to be heard from the mic. Simply let the microphone dry out. Put a bowl of uncooked rice in a closed box with the mic to absorb moisture. Protect air-studio mics from excessive mouth moisture with a good pop filter or foam windscreen (also good for mic hygiene). Another way to extend the life of your production studio microphones is to cover them when not in use.
In extremely damp locations, consider protecting the microphones with an impenetrable moisture barrier. Yes, the lowly unlubricated condom works wonders for keeping moisture out without too badly affecting the response and pickup. During a recent Winter Games, more than 400 of these impenetrable barriers were sent to the site to protect shotgun mics from snow and ice.
A shotgun or rifle mic is shaped like a long narrow tube with a series of slots down the sides. Protect these mics by storing them in their manufacturer-supplied cases. An alternative storage method is to keep the mic (with its foam windscreen attached) inside a piece of PVC pipe the same diameter as the mic/windscreen and loose capped at both ends. Just remember not to carry these through airport security.
Another thing to consider when using phantom-powered mics is the mic cable. XLR connectors will wear out with continued plugging and unplugging. Sometimes they become intermittent, disrupting phantom power and causing all kinds of noises. Make it a practice to regularly check and maintain your cables and replace worn connectors as necessary.
Finally, if you find that your expensive studio mics just don't sound as good as they did when you bought them, consider sending them back to the manufacturer for a tune-up. Many manufacturers can provide this service. Often a good cleaning and adjustments by the service tech can restore a microphone back to factory specs, adding many good years of life to your mic.
Microphones are an investment. With a little care, that investment can pay off for many years.
Steve Savanyu is director of educational services for Audio-Technica.
The broadcast loop
Proper dressing of a lavalier microphone's cable can help minimize cable noise. This technique, called the broadcast loop, is one way to do it. Start by mounting the microphone in the mic clip. Make a small loop with the cable below the mic, and secure the cable to the clip.
Thread the cable up, around and back down behind the clip securing the cable between the fabric and back of the clip. Note that the cable goes down behind the loop. Finally, dress the cable under the wearer's clothing, out of sight.
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