Mixing It Up
I can’t stand flimsy gear masquerading and marketed as “professional” equipment. As a veteran shooter with a large mortgage and two hungry, mostly unappreciative kids, I demand a lot from my tools that I use and depend on. These tools have become part of my family, and I rely on them in much the same way, for better and for worse, through thick and thin, for richer and for poorer.
When it comes to audio, your mixer is control central where you set levels, monitor audio quality, and apply limiting, padding, and filtration. Its layout of controls must be logical and easy to decipher. I’m a stickler for usability, and when a piece of gear is frustratingly designed, it is quickly relegated to a closet, back shelf, or eBay. A mixer’s gain and fader knobs must have a solid feeling and be large enough to grasp even with gloved hands—a particular need for documentary shooters in wintry, icy cold conditions away from the coziness of a comfy studio or corporate boardroom.
Since we’re discussing shooting on location, know that the mixer’s output meters should be clearly visible in bright sun whether at the beach or atop an alpine peak in glaring snow.
Working with top-of-the-line equipment may not always be an economic reality for video shooters. In a budget mixer, we can still look for a unit with a good signal-to-noise ratio, ample headroom in the recording section, and a decent limiter.
Mixers with insufficient headroom are problematic because they require recording at lower levels to avoid clipping, which can increase hiss. Mixers with poorly designed limiters can also produce unsatisfactory recordings; if pushed too far, loud passages may overwhelm the inputs and slam the limiters, producing severe distortion. This is why it’s often safer to set a more conservative recording level.
In general, shooters should take advantage of a mixer’s safety limiter. Because the limiter’s threshold is not normally reached, it normally has no effect on a recording. However, in noisy unpredictable environments like barroom brawls or crazed screaming matches in Operation Repo, the limiter kicks in gently to prevent clipping.
As in all areas of the technical craft, the audio workflow should be thoroughly tested before a shoot, with the uncompressed sound files from the camera imported into the NLE and reproduced over a high-quality monitor in a quiet environment.
One good measure of a mixer’s performance is its low-frequency response. The best field mixers use balanced transformers to provide isolation from the incoming source. Input signals are transformed magnetically; there is no electromechanical connection, as in the case of low-end mixers. For the shooter working primarily in reality TV, superior low-frequency response is integral to capturing clean professional audio.
Ideally, a mixer should interface easily with any microphone you might own. I continue to use my 25-year-old Sennheiser MKH-416, a trusted and devoted friend that has accompanied me literally to every continent on earth. From arctic cold to Amazon heat and humidity, this mic has earned its place in my family of Most Trusted Stuff; its ruggedness, reliability, and performance is unimpeachable. Your field mixer should be in this league.
All told, your mixer should ameliorate, not exacerbate, the noisy pots and -preamps that plague many low- and mid-range cameras. It should feature multiple microphone inputs with a wide gain range to accommodate various line levels. A range of 75 dB from mic input to line output is ideal. For most shooters, a mixer with a built-in 80-Hz (high-pass) filter is desirable because we usually want to suppress low-frequency noise such as wind and traffic.
Excerpt from Video Shooter: Storytelling with HD Cameras, Second Edition by Barry Braverman, © 2010 Elsevier Inc. All rights reserved.