Audio Mixers Essentials: Mixing your audio will improve your sound and enhance your videos.

An audio mixer is an important tool for achieving a good soundtrack. Whether you need to mix your audio in the field or in post production, there’s a wide range of audio mixers that will give you more control over your audio and better overall quality in your video.

Whether it is music or sound effects, sound gives the viewer all kinds of cues and clues. The music sets the tone of the scene, dialogue tells about the characters and the ambient sounds and sound effects add to the realism. Along with lighting, a clear, well-balanced soundtrack is often the difference between professional and amateur video footage. But to get good audio, you’ve got to mix it. In this article, we’ll cover the basic features of audio mixers and include a handy buyer’s guide to help you decide which model fits your needs and your budget.

What Good Sound Adds

Sound is something you usually only notice when there is a problem. Unfortunately, sound problems are common in home videos. Whether it’s distortion caused by audio input levels set too high, or ambient sounds like passing traffic drowning out dialogue, running your audio through a mixer can quickly solve many of your sound problems. Using a mixer in the field or in post production gives you more control over how your production sounds. By addressing your soundtrack in the same way you deal with your video, you’ll find you can achieve a dramatic increase in the quality of the audio in your video productions.

Back when motion pictures first started, audio wasn’t a problem because film pioneers like D.W. Griffith and Cecil B. DeMille were making silent movies. Even then, each theater provided either live music or recorded music to add depth and emotion to the pictures. These pioneers knew that good audio enhances the overall quality of a motion picture. Well-recorded audio will engage an audience’s senses and will ultimately be a more enjoyable experience.

What’s in the Mix?

An audio mixer combines audio from two or more input devices and lets you control the mix of the sounds. If, for example, you want to make a 30-second commercial, you’ll want to have music, narration, some dialog and perhaps a sound effect or two. If you connect your camcorder directly to your VCR, you’re stuck with whatever you recorded. You won’t be able to change the audio levels. With a mixer, however, you have the ability to control the audio. You can start with some music, bring the level down and then have your announcer talk while the music plays underneath. Throw in a sound effect toward the middle, if you want. You can even clean up any unwanted hums or distortion.

Passive vs. Active

In broad terms, there are two types of mixers: passive and active. A passive mixer, like the Azden Cam 3 ($79.95) is a small unit that does not use any power and has variable resistors that allow you to lower the level of an audio input. A passive mixer will not amplify or raise the audio level of a source. This device allows you to mix two similar sources, usually microphones, by bringing one down to the level of the other. Passive mixers are inexpensive, durable and easy to setup. The one drawback, though, is that you have little control over your audio levels. An active audio mixer, on the other hand, allows you to raise, lower and tweek levels to your heart’s desire. Active mixers come in all sizes and shapes. Sound studios have entire rooms dedicated to mixing boards. They can be huge and intimidating. You don’t need all of these features to mix sound well. You should initially be concerned with some basic functions that an affordable mixer will provide.

  • Faders

    A fader controls the levels going out to a mix. By sliding the fader vertically, or turning a knob, you can raise or lower an audio signal. The faders should be marked with level numbers so you can make a note of the levels at which you recorded or mixed your audio.

    One feature you might consider is the preset option. This allows you to preset a level so that when you bring up your audio source you can quickly set it at the exact level that you want. This is invaluable when mixing live audio or whenever timing is essential.

  • Inputs and Outputs

    The number of input jacks you’ll need depends on the type of production you are doing. You’ll want at least one mike input, either XLR,
    1/4-inch phone or mini plug depending on the type of mike you are working with. You’ll also want several line inputs for other devices like CD players, DAT players, tape decks or turntables.

    Some mixers have multiple output channels. This enables you to assign incoming sound sources to any of the outputs. Instead of having all levels going to the same outputs, you can add variety to your mix. This feature makes for a more complex soundtrack.

  • Mike/Line Switch

    Many lower-priced mixers have separate microphone and line-level inputs. Higher priced models, such as the Carvin C2440 ($1,000), will have multiple connectors for each input channel. Each channel will have a switch to change the input between microphone level and line level (such as a CD player or tape deck). Having switchable inputs with multiple connectors makes the mixer far more versatile, allowing you to easily adapt to the number of mike and line sources you are using. The line input is usually an RCA connector used for sources like a CD or tape player. Microphone inputs can be balanced XLR connectors or unbalanced 1/4-inch phone plugs. The different inputs are usually controlled by a trim knob, which allows you to reduce stronger signals and raise weaker ones. By using the input trim feature, you can adjust the input signal so it is within a useful range for the fader. This will help ensure fidelity in your recording.

  • Effects

    If you’re looking to add some pizzazz to a boring audio signal, look for mixers with built-in effects. Echo and reverb are the most common. These are usually found in the DJ-style mixers. Most other mixers have effects inputs and outputs for use with external effects units. Whatever effects you use, use them sparingly and appropriately. Resist the temptation to use every effect that comes with the mixer. Overused, these effects will make your video seem amateur.

  • Cue

    A cue channel lets you monitor a signal through headphones before you send it to the mixer to be recorded. This is a handy feature for previewing a sound and identifying any distortion or unwanted noise. A cue also allows you to cue up a sound source at the exact spot where you want to begin your recording.

  • Crossfader

    Located on most DJ-style mixers, a crossfader allows you to fade from one sound to another. It’s similar to dissolving from one shot to the next in video. It gives a smooth segue (an audio dissolve) from one segment to another.

  • Headphone Jack

    Most mixers come with a headphone jack that allows you to listen clearly to the signal you’ve chosen. When there’s a lot of noise and other distractions while you’re editing, headphones are an invaluable aid.

  • Equalizer

    The frequency equalizer allows you to make adjustments to incoming sounds to increase
    audio quality. You can control the tone of a sound by increasing or decreasing selected frequencies. For example, you’re out documenting a hurricane. You’re narrating the action, but as the wind picks up, the sound of the wind overpowers your narration. With the EQ feature, you can clean-up much of the wind noise. On some mixers, like the Carvin SM162 ($300), each audio channel has its own bass, mid-range and treble controls, giving you even more control over your finished soundtrack. The knobs are marked so you can record your settings and duplicate them again later.

  • Stereo vs. Mono

    If you’re using music from a CD or tape deck in your production, it’s a good idea to have a stereo mixer. When purchasing a mixer, look for the models with stereo line inputs. These provide a left and right channel that you can adjust. A stereo mixer allows more control over your sound. Even if you know that your final video soundtrack will be mono, it’ll sound better and be closer to what you envision in stereo.

  • Battery Power

    Do you want to mix your audio live in the field or can you wait for post production? Are you going to be videotaping where there are no electrical outlets? Usually the battery-powered mixers, such as the Studiomaster 42-DC ($90) and the Shure FP-42 ($1,240) are smaller and have fewer features so they use less power. If portability is important to you look for a mixer with the features you need. In most cases, the AC models will do. In a pinch you can always use extension cords or gas generators (although you’ll want to position yourself clear of the noise).

    Moving Pictures, Running Sound

    When shopping for mixers, once you know the features you are looking for, play with the consoles and find the one that feels best. Keep in mind that you will be spending hours perfecting your soundtrack. Easy-to-use knobs and switches that are spaced well and feel right are important and often overlooked. As you practice with your audio mixer, you’ll find that running a consistent soundtrack throughout your video is a challenge. But once met, the results will be well worth it.

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