Mix It Up! Audio Mixers Buyer's Guide

by Hal Robertson
February 2002

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You've got to love multi-purpose tools. Not those silly little pocketknives, but the big, beefy multi-purpose tools with pliers, screwdrivers, knives and saws. Regardless of the situation, you've always got the right tool hanging on your belt. The audio mixer is a multi-purpose audio tool in its own right. Whether you need a microphone pre-amp, volume or tone control, or a way to blend multiple sound sources on your video, the right audio mixer makes the job easy. And in video production, audio is half the battle.

Over the past few years, audio mixers have come to include more features and produce better sound quality, all at lower prices. Available in a wide range of prices, professional mixers are now within the reach of almost every video producer. If you want to shoot plays, concerts, panel discussions or talk shows, an audio mixer is a must. Many other shoots can benefit from mixing multiple mikes as well. Let's take a look at the many features of an audio mixer and examine how you can use them to deliver first-class audio for your next video production.

The Right Tool for the Job
There are several criteria that determine the situation in which an audio mixer will work best. While some mixers are built to handle the rigors of portable field production, others are best suited for your studio or edit suite. Sadly, it's almost impossible to find one mixer that works well in both environments. To help you make an informed purchase decision, we'll outline the features, pros and cons of each audio mixer category.

Field Mixers
Field mixers are designed for use while shooting on location, and are very helpful when you have two or more microphones to blend into your camcorder. When selecting a mixer for portable use, there are several things to keep in mind.

The first is power. If you plan to shoot in remote areas without the benefit of electrical power, your mixer must have a provision for battery power. Some mixers use common flashlight batteries, while others operate from a standard video battery pack. Still others may require a special battery or power supply that may eat into your budget. Don't forget to add the cost of batteries, chargers and other items that may not be included in the purchase price.

The next thing to consider is the size and arrangement of the mixer. On many video shoots, you might be both the camera operator and the sound person. In that case, your audio mixer should be small and lightweight, have a carry strap and easily accessible controls. Also, make sure the controls are not prone to bumping or movement and have clear, easy-to-read markings.

Before you buy, consider how many microphones you might need to mix. Two to four inputs are typical for portable mixers. Also, consider the type of connections needed for your microphones. Some microphones have three-pin XLR plugs, while others have 1/4-inch or 1/8-inch (mini) plugs. If you have to use adapters to connect your microphones to the mixer, keep in mind the adapter length and the fragility of the connections. It is always better to plug directly into the mixer if possible. Some mixers also include a line-level input for other sources, like CD or cassette players.

Level meters, whether needle-type or LED ladders, are very important for monitoring the output of your mixer. Too much signal can overload your camcorder's input, distorting the sound and ruining the audio. Too little signal and the audio will be noisy and difficult to manage. A headphone jack on the mixer will help with monitoring and will serve as a checkpoint for the audio signal.

Finally, consider your mixer's output connections. After all the microphones have been connected, blended and level-matched, you need a way to connect the mixer output to the camcorder or recorder. Professional video cameras often use three-pin XLR connectors for audio, but consumer and prosumer models rarely have more than a tiny 1/8-inch microphone jack for audio input. Make sure the connection from the mixer to the camcorder is simple, solid and reliable. If it requires a custom hookup cable or assemblage of adapters, be sure to include spares.

Studio Mixers
Back in the studio, another type of audio mixer comes into play. As long as electricity is available, a studio or tabletop mixer is well suited to many audio production chores. While this type of mixer shares many attributes with its portable cousin, many more options are present.

Although many companies manufacture excellent compact tabletop mixers, not all are created equal. Low cost is always an appealing factor, but it may not be wise to limit yourself to the cheapest mixer you can find. Often, a small increase in price yields a far superior product. On the other hand, the most expensive mixer may not be the best product for your specific application, either. Think carefully about how you use a mixer before you commit your hard-earned dollars.

Studio mixers are not limited to four microphone inputs. In fact, several manufacturers offer models containing 32 inputs or more; not that you need that many, but the option is there if you want to record a band or other performance that requires multiple microphones. Most tabletop mixers also provide phantom power for professional condenser microphones. In addition, studio mixers almost always contain a combination of microphone and line-level inputs. With this addition, you can easily combine and blend an assortment of microphones and music sources (CDs, musical instruments, etc.). Input connectors may be XLR, 1/4-inch, RCA or a combination of these. Take an inventory of the devices you plan to connect and be sure your mixer of choice provides proper connectors for everything.

Tone control is another option found on many tabletop mixers. Usually available for each input, tone controls allow you to further refine the sound by adjusting low, middle and high audio frequencies or bands. While some tone controls offer only simple bass and treble adjustments, other mixers provide three- and four-band controls, or even a 10-band graphic equalizer for the final output. The more sophisticated the controls, the more power you have to shape and refine your sound.

Pan control is another feature found on many studio mixers. When recording in stereo, the pan control allows you to move an audio signal to the left, right or anywhere in-between. Although most vocal inputs are panned to the center, it is nice to be able to place sound sources as you choose, all in full stereo. This technique is most often used in performance videos, like concerts. Choirs, orchestras and even applause sound stunning when properly mixed in stereo.

Studio mixers often contain more than one output. A full-featured model will contain balanced XLR microphone outputs, balanced and unbalanced line-levels and some auxiliary outputs for special effects. While you may not use all these connections, the option is there for future applications that you may have yet to consider.

As is the case with portable mixers, audio level meters are must-haves on your tabletop mixer. They provide an extra layer of protection with a visual indication of your audio levels. This final check on the way to the recorder is vital to insure that you will get a strong, yet undistorted audio signal.

Make It Sing
A good studio mixer provides several audio tools to simplify your production duties. As a mixer, it combines multiple microphones and line-level sources for video recording, but that isn't its only purpose. You could use your studio mixer to record voiceovers or sound effects directly into your computer. Or, you could hire musicians to record original background music, and mix the performance. With the appropriate software, your computer and mixer are a powerful audio-production team.

Another good use for your audio mixer is as a level-matching tool. If you use an analog video-capture card, you may have difficulties matching audio levels from different takes, not to mention different sources. Patch the audio from your raw footage tapes through the mixer just before the audio capture card. Using the volume and tone controls, it is easy to achieve a good audio balance. In addition, you'll eliminate recaptures due to overloaded signal peaks and save rendering time by applying tone adjustments prior to audio capture.

The Final Mix
Adding an audio mixer to your video rig is an investment that should pay big dividends over the years. You'll gain new capabilities and make everyday audio chores much easier.

With a good audio mixer, flexibility is no longer an issue, it's a given. You'll save time and headaches by simplifying complex audio hookups. Your audio should take on a new level of quality and you'll gain a power of control you never dreamed possible.

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