Surround Mixing Secrets

Surround Mixing Secrets… Nearly every motion picture, DVD and many TV shows are mixed in surround sound. Even sporting events use the technology to place the viewer inside the arena.

We’ve all gotten them: spam e-mails promising to reveal well-kept secrets that will make you healthy, wealthy and wise. The pitch is always the same: techniques or technologies exist to achieve your highest goals, but the government or some special interest group has suppressed the information, hoping to keep you enslaved forever. By freeing your mind (and your wallet), you can have these secrets sent directly to you, plus shipping and handling. Surround mixing may seem like one of those secrets but, this month, we’ll demystify the process and give you the tools and information you need to create professional surround mixes.

Shoot For Surround

Before we dig into this, let’s do a little research. Pick a movie – any movie – and drop it into a surround-equipped computer or home theater. Now, turn off the visuals. That’s right, we’re doing this test blind. Listen closely to the sound coming from each speaker. If possible, isolate each speaker, using the volume controls. Every speaker in a 6-channel surround system has a specific task. The center speaker usually holds the dialog, while the front left and right speakers support it with music and on-screen sound effects. The rear speakers provide a sense of space, with ambience and noises placed to create the illusion of being there. Finally, the subwoofer provides the kick that ties it all together.

Here’s one of the dirty little secrets: that soundtrack – and the soundtrack from virtually any Hollywood movie – is almost completely fabricated. Very few, if any, of the sounds you hear took place during the shoot. Dialog is typically replaced or augmented in a studio, while music, sound effects and other noises come from original or pre-recorded sources. What you hear at any moment is a mashup of dozens of individual sounds blended into a convincing whole. With this in mind, the production can take certain liberties with local noise levels and sloppy dialog recording.

It’s fair to say that none of our projects has a fraction of the budget or staff of a typical Hollywood movie, so we have to work smarter. Knowing that you will ultimately mix a project in surround, keep in mind that there are several things you can do to simplify the process in post. First – and if you do nothing else – get clean dialog. Use shotguns, wireless, whatever it takes to get the clearest, most intelligible dialog possible. Dialog is difficult and time-consuming to replace in post, so a little care up front will simplify your life later. Second, record the location. Before or after the talent does the dialog, record a few minutes of generic location sound in stereo. Even if the location seems quiet, these recordings will come in handy later. Finally, get separate recordings of real sound effects from the shoot. Use a shotgun to better isolate the sound and record on video if necessary. Car doors, cell phones and any other items that appear in the production will sound more organic if you have a recording of the real thing. Do these three things for every location and setup.

Posting the Mix

Once you have everything captured, logged and identified, it’s time for some mixing magic. Working one scene at a time, first establish a good clean edit, with all the shots in place. To quickly clarify a dialog edit, apply a simple high-pass filter to the track or clips. Start with a cutoff setting of about 90Hz to eliminate any rumble or wind noise. Adjust volume on a per-clip basis to even things out. If possible, keep the dialog on one track, and don’t worry if there are gaps – we’ll cover those later.

Before we start cluttering things up with music and environmental sounds, let’s drop in our sound effects and Foley. If your effects are short, you can easily place them all on a single track and label it SFX. Of course, audio tracks are free in your video editing application, so use as many as necessary, but keep them orderly and labeled. It’s easy to make your sound effects too loud, so play each in context, and adjust the clip volume for a natural sound. The same rules apply for any Foley you’ve recorded – footsteps, breathing and other human sounds. Place them on a separate track or tracks with appropriate labels.

Next – you guessed it – on a separate track, fly in your environmental or ambience recording. Unless the scene is specifically noisy, this track is just to fill in the gaps and place the viewer in the location. The volume should sound completely normal – as if you were sitting or standing at the camera position. The dialog volume should cut through the ambience, but try to mix as naturally as possible.

Finally, let’s include a little music to drive the mood of the scene; this goes on its own track too. Unlike the other audio tracks, the music track volume can rise and fall to suit the mood, action or dialog of the production.

Surrounded by Sound

So far, we’ve done everything but actually mix, but that’s about to change. Each video-editing application and DAW (Digital Audio Workstation) approaches surround mixing differently, but most share a common tool: the surround panner or encoder. This tool usually looks like a circle with markers for each speaker in a 5.1 surround system. Your job is to select the audio tracks and place them where you want in the surround field. While most surround mixing is static – using fixed locations – you can also automate the mix, allowing sounds to fly from front to back or even circle around the room.

For this article, we’ll stick with a simple static mix and start by placing the dialog track in the center speaker. If that sounds a bit too sterile, you can move the track back just a bit to include some in the front left and right speakers too. Next, place the sound effects and Foley recordings where they would occur naturally, based on the camera angle. If a car door slams on the left side of the screen, adjust the panner to reflect the location; do likewise for each of the other effects. Our ambience track is stereo, but we can use the panner to spread it to the rear channels. Start with a center-of-the-circle location, and move the track forward or back to achieve the correct balance for the scene. Use the same technique for the music track, but keep most of it in the front speakers, leaking some into the rear channels to fill things out.


Balancing Act

Getting the most natural-sounding mix takes a lot of finessing. With each addition to your mix, check the balance, and make volume adjustments as needed. Then, go back and tweak the surround placement until you’re happy with the results. You’ll do the same steps for each scene in your project. Yes, it’s a lot of work, but the end result is a video with a balanced, natural mix. Now you know the secret of mixing in surround sound.

Contributing Editor Hal Robertson is a digital media producer and technology consultant.

Side Bar: Dialog is Everything

I recently read an interview with actor/writer/director George Clooney. He was discussing his preference for recording real dialog on the set of Leatherheads. Most of his movies contain very few studio-recorded dialog pieces, and he likes it that way. He and his team went to extremes to achieve this in Leatherheads. There is a scene where a discussion takes place on a moving motorcycle. To get the recording, the crew turned the motorcycle into an electric vehicle. This allowed them to get the dialog they wanted and add the simple rumble of the bike in post.

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