Choosing an Audio Mixer

As any videographer worth his salt knows, the picture is only half the story. Mixing audio into your video is the other half.

Ask any audio engineer about audio in video and he’ll probably tell you that in many video productions,
audio gets treated like the poor, ugly stepchild. People spend hours perfecting how a video looks, and only
a few minutes or even seconds checking how it sounds. The result: a video that looks great but lacks total
entertainment punch because of weak sound tracks.

Most of the time, in terms of the topics covered in this column, we talk about how you can use
different editing tools to improve how a video looks. Titlers, edit controllers, monitors–they’re all things to
help you make better pictures in an edit session. It’s time we give audio it’s due and talk about editing tools
to make your video sound better, too.

This month, the subject is mixers, and how to pick the right one to help you edit a better sounding
video. We’ll start by covering some of the features you don’t want to miss in a mixer, and then suggest
how you might pick one to fit your budget and your videomaking style.

Mixing Basics

All audio mixers, from the simplest to the most complex, share one structure: an input section, a
control section and an output section. What separates the advanced mixers from the basic ones are some
added features and functions in each mixer section.

The mixer’s input section is where you connect the sound sources you want to add to your video
project. Signals from things like microphones, CD players, cassette decks, or electronic keyboards enter the
mixer at the input section. Mixer inputs are also called channels.

A mixer may have anywhere from two to 48 inputs or channels. The number depends mostly on
price. Mixers also have two types of inputs: low or mike level, which is for microphones, and high or line
level, which is for CD players, VCRs and tape decks. You can’t plug a microphone into a high-level input,
or a CD player into a low-level input and get good results.

You can connect sound sources to the mixer using two types of cables: balanced or unbalanced.
The RCA cables often used to carry audio between two VCRs are unbalanced. All mixers can use
unbalanced cables. But a mixer must have balanced input connectors to use balanced cables. Balanced
cables provide better sound quality, because they compensate for electrical and radio-frequency (RF)
interference. Most of the more expensive mixers have balanced input connectors, but cheaper models may
not. Mixers that support balanced cables will usually have three-pin XLR input connectors.

The plugs on unbalanced cables come in a few different shapes and sizes. These cables have either
RCA phono style plug, (like those that appear on many camcorders and VCRs), a quarter-inch plug or an
eighth-inch phone plug. Stores like Radio Shack sell plenty of adapters to help you convert a plug before
connecting it to the mixer.

The control section of the mixer is where you blend the various sound sources into one mixed
sound track. You adjust the volume of each incoming sound by turning knobs (called potentiometers or
“pots”) or by sliding slide controls (called faders).

The mixer sends the blended sound to the output section. A cable carries the signal from the mixer
output jacks to the audio inputs on your edit or record VCR.

On a simple, inexpensive mixer, the output section may be nothing more than an “audio mix out”
jack. Better models give you a master fader, which controls the output volume of the mixed sound signal.
With a master fader, you can slowly fade the entire mix in and out, or adjust its level during editing.
Without it, you must use the edit deck’s audio input level controls to fade sound in and out. If your edit
deck doesn’t have input level controls, you can only cut mixed sound in or out.

Intermediate Mixing Needs

Once you’ve edited a handful of projects, you realize there’s more to working with sound in a video
than just varying the volume level. Sometimes you need to adjust the tonal quality of the sound as well.
Maybe there’s some annoying tape hiss coming from the cassette you used for the background music.
Perhaps the lavaliere mike sounds a bit too “boomy” in the low-range frequencies. A basic mixer with level
faders won’t fix these problems.

Instead, you’ll need a more advanced mixer that provides an equalizer, or EQ, for each fader in
the control section. An equalizer lets you pinpoint a specific frequency range, and either boost or reduce its
presence in that particular channel.

For the tape hiss problem, you could “roll off” the high frequencies from the cassette deck to
reduce the hiss. To clean up the low-range “booming,” you can use the EQ to reduce the bass frequencies
coming from the microphone.

Because many camcorders record stereo audio, and many televisions can play stereo audio, better
mixers let you create your sound tracks in stereo. (Note: to record a stereo sound track, you’ll need two
available audio tracks on your master video tape.)

On a stereo mixer, each fader has a pan control whose function is similar to the “balance” knob on
a home stereo receiver. It determines where the sound appears between the left and right channels. With the
control turned completely to the left (counterclockwise), the sound will come only from the left channel.
With the control at the center or “twelve o’clock” position, the sound will come from both channels at
equal volume.

Better mixers will also have volume-level meters of some kind to show you the volume of
incoming and outgoing sound signals. Most mixers offer VU Meters, which provide an average sound-
level reading. Other mixers add a peak level indicator, which shows you the maximum sound level. Either
feature alone is an adequate tool for measuring sound levels. Having both ensures you’ll know exactly how
much sound your getting from your sources, and how much you’re sending to your tape.

Advanced Mixing for Video

If your productions include more than the occasional family video, you might need some of the
advanced features found on the best mixers.

If you want to add special sound effects like echo or pitch shifting to your video, you’ll need an
external sound processor. In most cases, you have to use a cable to carry the signal from the sound source
to the processor, and another to carry the signal from the processor to your edit VCR or mixer. Some top-
of-the-line mixers make adding these special effects much easier by providing an effects send and return
bus, also called an auxiliary send bus.

With an effects bus, you connect the external sound processor to the mixer, instead of the VCR or
sound source. By adjusting knobs or faders in the mixer’s control section, you determine what sounds go to
the external processor, and how much of the processed sound gets added to the final mix. It eliminates
having to plug and unplug all those cables every time you want an interesting audio effect in your video.
It’s very slick. Serious videographers find it essential for creating great soundtracks.

High-end mixers also may have EQ circuits that cover a broader frequency range than lesser
models. Instead of a bass and treble control for each channel, some mixers may have two or three controls
for just the low-range frequencies, and two or more for the high end. This gives you very precise control of
the tonal balance of an incoming sound.

If you use a condenser microphone, you know that it needs a battery to operate. Some mixers
provide what’s called phantom power for condenser mikes so you don’t need to worry about a battery.

Although you may need only one or two inputs now, chances are good that as your video
production skills grow, so will your audio expertise. As it does, you may find yourself wanting more low-
level or high-level inputs on your mixer. Some models offer inputs with a button to switch between low- or
high-level signals. That means you can connect two sources to each channel, and use the button to select
which one to use in the mix. It’s a nice feature because it lets you expand your production setup without
having to plug and unplug cables all the time.

The Right Mixer for You

You know the features on many of today’s popular mixers. Now you want to know how to pick one
that will work for you, right? Start by looking at how often you edit videos now, and how you think that
might grow in the next few years. Then think about the kinds of videos you edit, and what kinds of sound
tracks you want to create.

If you want to narrate your videos after you edit them, you’ll probably want a mixer with at least
one low-level or mike input. If you want to add music from a CD or cassette, you’ll want at least one high-
level signal input.

Videographers who only edit a few videos a year, and don’t expect that to change anytime soon,
might consider a good entry-level mixer. Azden makes the Cam 3 mixer ($80), with 2 mike inputs and a
high level CD or tape input. It’s a perfect fit for the occasional videographer who doesn’t need many bells
and whistles, but wants great sound tracks.

If you need more than three inputs, consider Audio-Technica’s AM200 ($250). It’s a four-channel
stereo mixer capable of mixing a variety of low- and high-level sources for video productions. It also has
some digital sound effects built in, including lasers, bombs, snare drums and telephones.

A number of special effects generators and video mixers include basic audio mixers that might
suit your needs. If you don’t already have a video mixer, you might be able to solve two problems with one
box. Sima makes the Video Ed/it 2X ($225) with a simple video switcher, microphone, cables and one
high-level input.

How many different sound sources do you use during editing? Two? Three? Ten? The ideal
mixing setup is to connect each sound source you might use in an editing session to a separate input or
channel in the mixer. If a mixer doesn’t have enough inputs to connect everything you want to use, you can
expect to plug and unplug a few audio cables during edit sessions.

If you have lots of potential audio sources, consider getting a mixer with eight or more inputs.

Peavy’s Unity 1002-8 ($400) has eight switchable inputs, stereo output and a three-control EQ on
each channel.

Mackie offers the 1402VLZ ($599), which has 12 channels, stereo output and auxiliary send for
using external effects.

Don’t Forget: Sound Matters

In a video, scenes that don’t have clear sound tracks to accompany the visuals leave audiences
frustrated or bored. If viewers can’t easily hear what’s going on in a scene, they’re less likely to make
sense of what they see. If they have to strain to understand voices or other sounds, it takes away some of
their enjoyment of the video.

A mixer can help you 1) restore the natural balance between sound and pictures in a video, 2)
blend a variety of sounds to create a dense, rich soundtrack, and 3) create smooth transitions from one
sound to the next. Doing all of these will help capture the viewers’ imagination and keep them entertained
as they watch your video.

The Videomaker Editors are dedicated to bringing you the information you need to produce and share better video.

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