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Hour 7. Adding Audio > Connecting Mics to Your Camcorder

Connecting Mics to Your Camcorder

Surprisingly, this is the place where most mic problems arise. Most consumer and prosumer camcorders do not have decent mic input connections. They typically do not have enough amplification to “hear” low-impedance mics like standard handheld mics. What's more, they use mini-plugs, whereas most professional mics use rugged, reliable XLR jacks. What you may need is a transformer with an XLR to mini-plug cable to increase the impedance and allow you to connect your mic to your camcorder. Such transformers are passive, meaning they do not require electricity. Shure has just such a transformer—the A96F—for $54. If you use a powered mic such as a lavaliere, you may need only the XLR to mini-plug converter cable.

Getting the Most from Your Mics—Expert Audio Tips

When I considered whom I'd tap for audio expertise, only one name came to mind: Shure, Inc. Throughout my TV news and video production career, Shure mics have been the staple in our audio kits.

This 77-year old company is a world leader in microphone technology, playing a roll in audio history from the Japanese surrender ending World War II and President John F. Kennedy's inaugural address to Woodstock and the 2002 Winter Olympics, where Shure's wireless systems captured all the opening ceremonies' audio moments.

Shure's “Elvis mic,” the Unidyne, kicked things off when the company first introduced it in 1939. Frank Sinatra and the Rolling Stones field-tested the SM58—the world's best- selling, all-purpose vocal mic, introduced in 1966. And now groups such as 'N Snyc and D'Angelo rely on Shure's Beta Series.

Shure put me in touch with Chris Lyons, a Senior Engineer in Shure's Applications Group. In his 12 years with Shure he has served as Technical Liaison for Shure's broadcast customers and as Product Line Manager for Wired Microphones. Chris has presented hundreds of audio training seminars to broadcasters, educators, government agencies, and audio/visual production specialists. He has written and edited numerous articles and technical papers, including the booklet Guide to Better Audio for Video Production, available for free download at http://www.shure.com/booklets/techpubs.html.

Chris offers this expert advice:

  • Always place the microphone as close as is practical to the sound source. Every time the source-to-mic distance increases by a factor of two, the sound pressure level (SPL) reaching the mic decreases by a factor of four, making clear sound pickup progressively more difficult. This is called the inverse-square rule, and it applies whether the distance increases from 6 inches to 12 inches or from 6 feet to 12 feet. This means that the talker-to-mic distance must be cut in half to cause a significant improvement in sound quality.

  • Use the fewest number of microphones necessary for the situation. People sometimes have a tendency to “over-mic” a shot, using three or four microphones when one or two would be sufficient. Using excess mics means more background noise pickup, greater chance of feedback or “tin can” sound, and more levels for the operator to keep track of. If additional mics don't make things sound better, they probably will make things sound worse.

  • Advice for using a handheld mic: Whether held in the hand or mounted on a stand, place this mic about 6–12 inches from the talker's mouth, pointing up at about a 45-degree angle (see Figure 7.4). With some types of microphones, holding the microphone very close (3–6 inches) will cause additional emphasis of the lower frequencies (known as proximity effect), resulting in a “warmer,” bass-heavy sound.

    Figure 7.4. Proper placement for a handheld mic.

  • Advice for using a lavaliere mic: For best results, clip a lavaliere mic on the outside of clothing, about six to eight inches below the chin. You can clip the mic to the collar of a shirt or blouse, but sound quality in this position tends to be somewhat muffled because some high frequencies (which contain consonants) do not fully wrap around to the area under the chin.

  • Advice for concealing a lavaliere mic: Concealing the mic gives your production an extra level of quality. Make sure you keep both the microphone and the first few inches of cable from rubbing against either the body or clothing, which will cause noise. Try taping the “lav” under the shirt collar near the opening in front. The cable can be routed around to the back of the neck, over the collar and under the shirt. Alternatively, tape it to the interviewee's eyeglasses on the inside by the temple. Route the wire over the ear and down the back.

  • Advice for using a surface mount mic: These are great for panel discussions and work best when positioned on a smooth, flat surface, such as a table or desk. A thin piece of soft foam rubber or a computer mouse pad underneath the mic helps minimize problems created by surface vibrations. Small surfaces—less than three feet square—reduce the pickup of low frequencies and may improve the clarity of deep voices by reducing “boominess.”

  • Advice for using a shotgun mic: Avoid aiming shotgun mics at hard surfaces such as tile floors, brick walls, and flat ceilings. These surfaces reflect background noise into the microphone or cause the sound to be slightly hollow. Place a heavy blanket on a reflective surface to provide some sound absorption. Shotgun mics are more sensitive to wind noise than standard microphones, so use a foam windscreen and don't move them too rapidly. A rubber-isolated shock mount will help control handling noise.

  • Use only low-impedance microphones. Low-impedance or “Low-Z” mics (less than 600 ohms) allow you to use very long runs of cable (more than 1,000 feet) with negligible loss of sound quality. “High-Z” mics (greater than 10,000 ohms) lose high frequencies and begin to sound muffled with 20-foot cables. The impedance of a microphone should not match the impedance of the input to which it is connected. Matching the impedance causes significant signal level loss. Always connect low-impedance microphones to higher-impedance inputs—preferably 5 to 10 times greater. Inputs on professional mixers typically have an impedance of 1,000 ohms or more.

  • Tips on using wireless systems: Try to keep the distance from the transmitter to the receiver as short as possible. Always do a “walkaround” with the mic before the event. If dropouts occur, try moving the receiver a few feet and repeat the walk-around. Dual-antenna “diversity receivers”minimize dropout because it is unlikely that the signal to both antennas will be interrupted at the same instant. If possible, do your sound check at the same time of day as the event to discover whether there are any nearby users of your wireless frequencies. When using belt-pack-type transmitters, make sure the antenna cable is hanging straight. Coiling it up in the wearer's pocket significantly reduces transmission distance. With handheld transmitters that have an external antenna, discourage users from holding their hands over the antenna to avoid reducing transmission range and increasing dropout.

  • Use “balanced” cables and connectors. Their metal shielding keeps the audio signal free of interference from things such as florescent lights, dimmer switches, and other audio or electrical cables. Use cables with braided or mesh shielding. They are more resistant than metal foil shielding to cracks or tears, which cause electrical shorts.

  • Plan ahead. This is the most important thing you can do to improve the audio quality of your productions. When you set up your equipment, look for things that might cause a problem with your audio—air conditioning ducts, noisy doors, fluorescent lights, and so on. Check for things that you can use to your advantage—sound-absorbent carpeting or a built-in PA system. Experiment with different mic placements but don't gamble an important project on a method you've never tried. Monitor your audio and listen carefully for anything that sounds unnatural. As the saying goes, “If you notice the sound, there's something wrong with it.”



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