Surround Sound Mixing – Part 4 of 5
This is a guest post by mix engineer, Unne Lilijeblad over at www.mix-engineer.com. This is the fourth article in a five part series about his experience with mixing in this still under utilized medium for listening to music. Recording and Mixing in Stereo. This week he talks about Mixing in Surround.
Mixing in Surround
Now what about surround? Obviously, the panning of mono sources in a surround mixing environment works very similarly to the way it works in stereo. It gets more complex of course, as the panner has to divide signals between more speakers, and you now have a three dimensional sound field with both an x and a y-axel, rather than just a simple two dimensional field between left and right. The panning via delay technique works too of course, and naturally, the two can be combined.
There are issues with mixing this way though. Since the same signal gets sent to many speakers (which is what happens with the surround panners built into most DAW software and Digital Consoles capable of surround mixing) the location of the listener becomes very important. Unless he or she stays exactly in the center of the surround field, you’re going to end up with arrival time differences between the signals originating from the different speakers. And this time, these are not intentional differences, decided upon by the engineer, but rather, they depend upon the listener’s location which, of course, the engineer cannot control, resulting in your pan positions changing as the listener moves. And as you have more speakers reproducing the same signal, you’ll get more comb filtering effects, and ultimately a more cluttered and less clean sound.
But how about true surround recording techniques equivalent to the X/Y and ORTF methods used for stereo? Yes – There are a number of surround recording techniques in use, most of them based on, or extensions of, existing stereo recording techniques. The limiting factor with these methods however, is that the panning position for audio sources largely gets decided by how they were placed in the space where the recording took place. Sure, levels sent to the different surround speakers can be tweaked and manipulated during mixing, but only so much, because at some point, where the level gets too low or too high in some of the speakers, you loose the realistic feeling of the original recording, which defeats the purpose of having recorded that way in the first place.
In the next installment Unne will discuss MSS - Multi Stereo Surround.