Reference: StudentFilmmakers Magazine, February 2007. Stereo vs. Mono Recording: And the Impact of Surround Sound by Bryant Falk Pages 34 – 35.
From the audio side, recording all started with mono; silent movies going to sync sound, and all with one microphone. Though practical, mono recording was still missing something. We do have two ears after all. Our ability to locate distance and direction by using our two ears in conjunction with each other had been ignored for quite some time.
With the arrival of stereo sound came the ability to locate audio within a given space. It also allowed us to create a sense of space. A car driving through our scene from left to right can actually sound like it’s moved from our left ear to our right ear! The irony to this is how many people think you need to record in stereo in order to achieve this car trick mentioned above. Not so.
The answer to whether or not you should record in stereo is: it depends. Many mono recordings can be enhanced in post to simulate a stereo field. Like the car sound in the above example. Take a mono recording of a car, correctly apply a Doppler shift, pan and sync it correctly to your moving image. Make sure the proper reverb and delay are in place, for example, if your car is driving through a parking garage, and make sure that you’ve applied appropriate EQ and volume to match appropriate distance –and relative to the music mix or other audio items going on in the scene at the same time. So the next question would be: When and do I need to record in stereo at all?
Here is an example. You’re recording audio for a remake of Joel Olianky’s The Competition. Only this time they’ve hired actors who really do play piano, and the director wants to capture the piano/dialogue scene in its entirety.
The following is a list of microphones we will need for the scene:
1) Stereo mic setup for the grand piano (XY or coincident pattern)
2) Two lav microphones for the talent
3) Boom mic for safety
Remember, a real stereo microphone setup isn’t just relating two separate audio tracks. They work together to create a spatial relationship with the room and the item you are recording. Simply put, stereo recording a grand piano in a basement should sound different than recording that same sound in a church hall. When stereo recording, we actually want to capture the sound of the audio as it relates to that specific space. But not too much. Leave room for the mixer to expand it further if need be.
If all of the above microphones are needed to be on at the same time, some time shifting will need to be applied to the tracks to prevent some nasty comb filtering. This adjustment is usually handled in post on a Pro-Tools rig or equivalent. If only the lavs are needed, then it cuts to the stereo piano, then back to lavs, you can simply mute the offending track until it is needed.
Now let us jump to another example with Steven Spielberg’s Empire of the Sun. The scene is when the camera assumes the little boy’s perspective, and we are wandering through the barracks towards John Malkovich. Imagine this time they want to re-shoot and pull John Malkovich because his agent wants another 10% for the interplanetary distribution rights (they want to air the movie on a new space station hotel – crazy but possible).
Potential mic setup:
1) Stereo mic riding with camera on dolly shot
2) One boom mic for incidentals.
If shot with the intention of audio (meaning the people are creating a real walla track), the stereo mic will really create a sense of movement as the camera pans back and forth. Also, as we move forward through the barracks, the stereo setup should create the illusion of characters moving from in front of us to behind us. This can be a very powerful effect in a scene. Can it be created in post? Of course! But if you are on a tighter budget, this option may save you some serious coin and time later in post. Also the magic of capturing spontaneous performances can be priceless.
I mentioned “incidentals”, on the second item. These would be the select comments you may want to punch out of the walla track to add impact. Say overall we are hearing suffering sounds from those trapped sweating these barracks. We may, (to both drive story forward and add emotional impact), want to add some specifics that punch through. For instance, a woman commenting, “There’s no place to bathe,” or a young man yelling obscenities as he starts to panic. These are recorded in mono on the boom and peppered into your stereo track with panning where desired. So with a combination of stereo and mono tracks, we are actually able to paint a very effective audio landscape for a film or TV project.
Now comes a new revolution. Actually, it’s not new at all. The fact that it’s beginning to pervade into every home in America is what’s new. It’s called surround sound, and it’s rolling in like thunder, (which would sound great on a surround system).
The basic surround sound setup is called a 5.1 system. Six speakers make up this system.
2) Front left
3) Front right
4) Back left
5) Back right
6) Woofer for low frequency effects, (LFE)
Surround has the distinct advantage of allowing a lot more control of sound location in a room and a larger, “Sweet Spot”, in which to experience the audio of your movie. Also, a lot less psycho acoustic tricks are needed. For example, if you want the train in your movie to sound like it’s coming from behind you, it’s just a matter of moving the train audio from the back speakers to the front. In a stereo format, we would have had to use some complex delays to create the illusion of the train travel. Also, with stereo, there is a smaller spot in the room where it actually would sound the way we intended. So at the end of it all, a surround system can make things simpler. Unfortunately, there are still many TV’s and even movie theatres that are not equipped to handle a full surround mix. Also, the storage requirements are much higher, as well as the cost to prep a final mix. I would always recommend even if you plan on doing a surround mix that you also create a stereo mix. The surround will not always collapse cleanly into a stereo, so keep your ears open to anomalies!
One thing is for sure. As technology rolls forward, audio will continue to progress. The changes will be as simple as a new format for recording to a virtual surround system that incorporates the latest hypersonic technology allowing two towers to do what it takes six speakers to do now.
Bryant Falk has been a producer and engineer for over 12 years working with such clients as The Ricki Lake Show, Coca-Cola, Sport Illustrated, Valley National Bank, and MTV’s The Shop. His company Abacus Audio handles many aspects of the audio production field from creative and production to mixing and final output. http://www.abacusaudio.com/