The Role of an Audio Mixer in a Video Editing Suite

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Deleted scenes often end up “on the cutting-room floor,” but how did specific pieces of equipment end up on the editing-room desk? It’s common to see a computer keyboard and multiple video monitors on the desk of every video-editing station, but there’s usually another piece of equipment that may seem somewhat out of place: an audio mixer. In this article we’ll explore the audio mixer’s role in a video editing suite, offer tips on how they can be used and suggest specific models of mixers and key accessories to support them.

The main job that an audio mixer serves in an editing suite is to act as the master volume control. You also use them to select the source that you want to listen to. Professional editing suites are usually equipped with studio monitors, which you can think of as the speakers that are used in recording studios. The main audio outputs of the computer-editing system will usually be plugged into the audio mixer, and the outputs on the audio mixer will then be plugged into the studio monitors. This way you can use the volume control on the mixer to control the volume of the speakers in the suite. The editor will also connect their headphones to the mixer to monitor the playback.

Many post production facilities have a “machine room” that houses most of the important hardware associated with the editing suites. This means that the computer for a specific editing suite can sometimes be a few doors away, rather than physically present in the room with the editor. In these situations, there are often a series of cables that are patched into the editing suite that provide connections for the video monitors, computer keyboard, etc. Cables are also provided for the sound, which are connected to and controlled by the audio mixer.

The mixers that are used in editing suites are typically compact in size, yet offer enough channels to connect several pieces of equipment. In the recent past, video tape decks were often used in editing suites, both for the logging and capturing of footage into the computer, and for recording completed projects back to tape. When tape decks are used, the main audio outputs of the tape machine are connected to the mixer, so you can monitor their playback through the main speakers in the editing suite.

Even though DV tapes are being used less and less frequently, audio mixers are far from being obsolete in the editing suite. Professional editors still rely on VTRs and other kinds of decks for their work. When creating a real-time master of a final project on an external VTR, it’s best to monitor the audio from the connected deck (as opposed to listening to the playback from the computer/editing software). You want to hear what the audio sounds like at the destination, not at the source. Therefore the main audio outputs of the VTR would be patched into an audio mixer.

If your workflow never involves external machines like VTRs, audio mixers are still useful in more modest setups. It’s common to burn projects onto a DVD or a Blu-ray disc for a client or an archive. An essential step in creating a disc is watching the playback afterward to make sure there are no errors, unwanted artifacts or anomalies in the final product. The best way to hear if the audio turned out properly is to listen to the disc on your active studio monitors as you watch. This is done by connecting the disc player’s audio outputs to inputs on an audio mixer.

In the event that you hear something wrong with the sound when you’re playing back an optical disc or listening to a VTR, a common practice is to go back to the project in the computer, find the same spot where the problem occurred on the external machine, pull up the sound of the computer on the mixer, and determine if the problem is present in the project itself, or if it was an error that occurred in the external hardware.

The audio mixers that are used in editing suites typically feature XLR microphone inputs and preamps (in addition to stereo line-level inputs). This makes it possible to connect a microphone to the mixer, and if your computer system features audio inputs, it’s possible to record voice-overs directly into the computer. You can learn all about voice-over microphones and equipment in this B&H InDepth Buyer’s Guide.

One of the most popular mixers found in video editing suites is the Mackie 1202-VLZ3. It’s a great candidate for an editing suite because it’s incredibly compact, yet it still features an excellent build quality and provides outstanding sonic performance. There are similar mixers available that have more affordable price tags, but the first two things that you give up are sound quality and build quality. Mackie mixers have become standard in professional editing facilities because they have proven themselves to be reliable and versatile pieces of equipment for broadcast-media production.

The first four channels of the 1202-VLZ3 feature XLR inputs (each with an XDR2 preamp) and a single 1/4" line-level input as well. This is where you can connect microphones to perform voice-overs (however, this requires that you have either an audio interface or video-capture hardware with audio inputs). The next four channels all feature stereo line-level 1/4" inputs (so technically they are eight channels, not four). The stereo line-level channels are a great place to connect the main outputs of your video-editing system, as well as the stereo outputs of DVD players, Blu-ray players and VTRs.

If you need to connect more than six stereo sources to the mixer, or if you prefer the feel of real volume faders (the 1202-VLZ3 is all knobs and buttons), the Mackie 1402-VLZ3 is a great alternative. The 1402-VLZ3 features a very similar layout to the 1202-VLZ3, but it has two more channels with XLR inputs and preamps, and it has 60mm channel faders. Even though it has a bit more going on, the 1402-VLZ3 is still a very compact mixer and measures only a few inches more than the 1202-VLZ3.

A really nice feature that both of these mixers have is a small button that changes their main outputs from line level to mic level. This is handy when you need to connect the mixer to a video camera. For example, if you’re hired to shoot a panel of people at a conference, you could bring your Mackie mixer along and use it to mix multiple microphones into your camera. You could connect several microphones to the mixer to capture the voices of the people on the panel, and if the video camera being used doesn’t have line-level inputs, you can simply switch the mixer to output a mic-level signal to connect to the camera’s microphone input. These mixers do not run on batteries, so they would need to be plugged into AC at the shoot, but still, it’s nice knowing that your editing suite mixer can be used in production as well.

If you’re considering adding an audio mixer to your editing rig, but you don’t currently own studio monitor speakers, there are many high-quality options to choose from. A popular and cost-effective choice is the KRK RoKit 5 G2 active near field monitor. They’re sold individually, so you need to purchase two for standard stereo. The RoKit 5 is famous for packing a lot of sound into a very compact footprint. The sound is very clear, punchy and accurate. Accuracy is a key factor in studio monitors. You don’t want to use speakers that accentuate bass, or that sweeten the mids or highs. You need speakers that flatly reproduce the sound you are working with, so you can make informed decisions on how your project sounds.

If you’re using speakers like the RoKit 5 models and you plan on resting them on your desktop or on speaker stands, it’s important to decouple them from the surface they’ll be resting on. When a speaker like this is making direct contact with a desk or a stand, sound vibrations will resonate into the physical object that it’s resting upon. The problem is that low frequencies will be accentuated as a result of this resonation, and the accuracy of what you’re hearing will be artificially degraded. You can avoid this issue by using a decoupling system like the Auralex MoPADs, which create a simple foam layer between the speaker cabinet and the surface. Vibrations in the speaker are absorbed by the foam and not transferred to the physical object it’s resting on.   

If you prefer to use only industry standard equipment, you should pick up a pair of Genelec 8020B Active Nearfield Monitors for your suite. Like the RoKit 5, the 8020B speakers are sold individually, so you need to buy two for standard stereo. The Genelec 8000 series is very popular in professional facilities. These speakers provide very accurate reproduction of sound, with a particularly wide sweet spot, so you don’t have to be positioned perfectly between them to hear an accurate representation of stereo left and stereo right. They feature an integrated “Isopod,” so purchasing additional decoupling accessories is unnecessary.

If you’re going to be using either of these speakers with a Mackie mixer, the cable that you would use to connect them is a 1/4" TRS male to XLR male, like this Comprehensive EXF Series cable. The Mackie mixers have a special section for the “Control Room.” There are dedicated Control Room 1/4" TRS outputs on the rear. This is where you connect the speakers. On the face of the mixer, there’s a dedicated CTL Room/Submix volume knob. This knob controls the volume of the speakers connected to the Control Room outputs. Adjusting the level of this knob does not alter the level of the Main outputs.

The great thing about using an audio mixer is that it’s a very versatile piece of equipment. It can be used to carry out the tasks described in this article, as well as do a thousand other things.

Thanks for checking out this B&H InDepth article. If you have any additional questions or comments about an audio mixer’s role in a video editing suite, such as how you use your mixer in your studio, we’d love to hear about it in the Comments section below.