Tapping into an existing audio mixer often results in a clearer audio track.

Say your skills at video production have earned you a good reputation locally, allowing you to land a job videotaping an important event. The event includes music, speaking and some short skits. It’s quite a production, taking place on a large stage with a good-sized indoor audience area. A professional company will handle the sound reinforcement and lighting duties. Are you up to the task of providing the same level of production quality for the video? You weren’t going to rely on your camcorder’s built-in mike to capture the event, were you?

Do you remember, as a child, being impressed by the unique sound of your family car’s horn inside a tunnel? The reverberation characteristics of tunnels are amusing, and provide one of life’s really cheap thrills. However, by now you probably realize that you wouldn’t want to try to listen to, or try to record, music or speech inside a tunnel. The reverberation characteristics that are so amusing with the car horn would now be downright annoying because they interfere with your need to hear and understand clearly.

In general, the built-in microphone on a camcorder will give you somewhat of a “tunnel” sound. It picks up lots of ambience and reverberation from the environment, extra sounds that compete with what you really want to hear. In the case of your local event, these sounds include sound bouncing from the walls of the building, audience coughs and sneezes, even your own breathing. A direct feed straight from the sound company’s audio mixer, on the other hand, will provide a clear, professional sound.

The techniques and equipment outlined here will serve as a guide to making a direct connection to the audio source. Remember, the promoter hired the sound company because they have the ability and equipment to capture excellent sound. By using a direct connection to their equipment, you should be able to produce a more powerful audio track, and thus a more professional overall production.

Maximum Impact

If you don’t suffer from a limited budget, you could produce your soundtrack in the same manner as professional video production companies do. They take a direct feed from every audio input at the sound company’s console, running those feeds to their own console to do a separate mix for the video. This is optimum, because the sound company is mixing for the audience area and for the sound system. This means the soundperson has made adjustments to the signal to suit their system’s needs–not yours.

The next best thing would be to take a feed from the sound company’s monitor mixer. If you can get the operator doing the monitor mixes to “mix” you a separate feed, this would be an excellent option. Unfortunately, all the monitor outputs are often in use, and the sound company wishes they had a console with more outputs. Don’t expect this option to happen very often.

Sound You Can Live With

Unlike professional production companies, few amateur or semi-professional videomakers can afford the expense of doing a separate audio-for-video mix. But excellent audio does not necessarily have to be expensive–a direct audio feed should set you back no more that the cost of a connector or adapter and some audio cable. Your long cable with the connector/adapter will enable you to tap into the console and benefit from the skills of the professional operator.

Thankfully, most mixing consoles have a few outputs that are never used. Some of these contain the main house mix, while others may offer a completely different mix. While a separate mix for your video is better, just about any form of the audio signal will be superior to what a camera-mounted microphone will be able to pick up.

You will find there are generally two types of physical audio connectors used by most consoles, and three different audio levels to contend with. The 1/4-inch phone plug is the most common connector on music consoles, while the 3-pin XLR connector is common on the more professional consoles. Most 1/4-inch phone plug outputs are unbalanced, as are most VCR audio inputs and camcorder mike inputs. Generally, in this case, the signal is on the tip and the sleeve is ground. In the case of a balanced 1/4-inch connector, the tip is the positive (+) signal, the ring is the negative (-) signal, and the sleeve is ground.

Most, though not all, XLR console outputs are balanced. The international standard is pin 2 (+) signal, pin 3 (-) signal and pin 1 ground. One half of the balanced output will easily drive the unbalanced input of a video recorder or camcorder. However, the output level of a balanced console may be too high. More on audio levels in a minute.

Where To Connect

The output labeled “mono” on some consoles is the preferred output for a monophonic (not stereo) audio-for-video feed. This output combines the left and right signals from any stereo source or stereo mix into a single mono signal. At the mono output you are sure to get all the signal, not half of a stereo mix.

You probably don’t want to connect to the monitor, effects or auxiliary outputs because the signal on these outputs is mixed separately for a very specific reason. These feed stage monitors or effects devices like reverb units (remember we are trying to avoid reverb). The mixer’s output may have some reverb mixed in, but just enough to enhance the audio, not enough to cause problems. A cooperative audio engineer will guide you to the appropriate output if one is available.

In the event an appropriate output is not available, you might still be able to get the sound company to give you the feed you want if you have a distribution amplifier (commonly called a DA). The DA takes a mixer output and splits the signal to create multiple outputs (usually four), each isolated from each other. One output of the DA serves to replace the output you plugged the DA into, and another serves as your audio-for-video send. Isolation between the four outputs insures that any equipment you connect to one output has no effect on any of the other outputs. The last thing you want to do is to disrupt the efforts of the sound company.

Making Do

If the audio engineer or sound company is just not willing or able to work with you, you will have to drop down a notch in quality. But all is not lost–it’s possible to clip onto a speaker lead to tap into the signal going to the speakers, effectively giving you the same signal as from the mixer. You will need a special adapter designed to attenuate the signal. However, if the sound company isn’t overly helpful, they probably won’t let you touch the speaker wires. Besides, many sound companies use sealed connectors which would not allow connecting to the speaker wires even if you wanted to.

In this case, it’s time to get creative. If all the direct connection options have fallen by the wayside, you may want to put an off-camera microphone to work. With a good microphone and a long cable, you can overcome much of the overly-reverberant tunnel effect by placing the microphone in front of the main speaker system. It’s not as good as a direct feed, but it’s better than using a camera-mounted microphone. The only precaution with this approach is to pay attention to the speaker you are placing the microphone in front of. Most sound companies use speakers that have multiple drivers in them, each of which carries only a portion of the audio frequency range. This makes your microphone placement somewhat more critical. In general, the further you place a mike from such a multi-driver speaker system, the better. Move it back too far, however, and you lose the benefits of the close miking. Placing the mike six to 10 feet from the speakers is a good place to start.

If you already own a wireless microphone system, a convenient approach would be to place the microphone/transmitter in front of the main speaker (hopefully in a protected location) and place the receiver back at the video recorder or camcorder. The same precautions apply to the wireless microphone when placing it in front of a multiple-driver speaker system.

Levels

There are three audio levels you may encounter in trying to make a direct connection to an existing audio system. By far the most common will be “line-level.” This is the audio level used by consumer electronic A/V equipment, and by most audio and sound equipment sold in music stores. Audio signals at this level will drive the line-level inputs on any of your video equipment or any independent mixer you might want to use. This is the most common level you will face.

Professional-level outputs (+4dBm, in tech-speak) on large production consoles and most broadcast equipment may present a problem in that they are capable of overloading the inputs of line-level audio equipment. One solution is to use an audio “pad” or “attenuator,” a device to bring the level down before it reaches the input. Most pads are passive devices (no electronics). You might also use an active level-matching interface box, which is better for some applications.

At the other extreme is the microphone-level signal, which has just a tiny fraction of the strength of the other two. In some cases, you may need to go into your video equipment with this much-weaker signal. This would be the case if your only option is to input the direct audio feed through the microphone input on a camcorder. If you’re using a wireless receiver to get the signal to the camcorder, chances are the portable receiver has a microphone level output. If you’re running a long cable from a microphone positioned near the loudspeaker, then all you need is an adapter to get into your camcorder. If the signal is at line-level, you will need a “direct box” to make the connection.

A direct box converts a line-level signal into a balanced, microphone-level signal to feed the input of a mixing console or camcorder. Most sound companies have direct boxes available, though you probably won’t want to try and borrow one from them since they have their hands full with their own situation. You can buy one through most sound companies, pro audio shops or even through music stores that sell sound equipment.

Direct boxes are available passive (with just a level- and impedance-matching transformer inside) or active (using electronic circuits). A passive direct box uses no battery or other power source, but the transformer needs to be well-designed in order to prevent sound quality loss. An active direct box may sound better, but it requires a source of power. You should replace batteries every time you start an important job. If the batteries go down, your audio goes away.

Regardless of which signal level, adapter, connector or interface box you use, always try to be present at the sound check. This low-pressure rehearsal allows you to work out any technical problems before the actual event begins.

Hearing Is Believing

Getting a direct audio connection may seem like a complicated new process. In many ways it is, but the difference in audio quality is outstanding and well worth the effort.

When mixing sound for a musical group, I once had to work very hard to convince a videomaker to accept the audio feed the promoter had specifically instructed me to provide him. He argued with me that the camera microphone would do an excellent job. The finished videotape made him a believer in direct audio. At the point in the show where I finally convinced him to “plug in,” the audio suddenly sounded professional. He was surprised; the musical group was delighted.

If you want your efforts as a videomaker to have a professional impact, professional-sounding audio is a must. Don’t let poor audio bring down your best video production efforts. Get connected–use a direct audio feed if at all possible.

LEAVE A REPLY

Please enter your comment!
Please enter your name here