There exists a whole other audio dimension at right angles to the one we create with our pan pots. It’s called “depth”. Depth is the sense of nearness and farness of sounds in a mix.
Pan pots place images of recorded instruments and voices anywhere, left-to-right, in a line between our monitor speakers. But what about front to back? There’s no pan pot labeled “close-far”.
Still, we can create that extra dimension in our mixes. We can make mixes not only big (with panning), but also deep. Our mixes can have 3-D spaciousness as well as left-right extension.
So how does this work? Think about what happens in real life when a person speaks in a room, and walks away from you. Their voice gets more reverberant, and it loses some highs. When they are close to you, you hear mostly direct sound from their mouth, and very little reverberant sound bouncing off the room surfaces. When they are far from you, the direct sound from their mouth is relatively weak compared to the room reverb.
So, we perceive a high direct-to-reverb ratio as sounding close. We hear a low direct-to-reverb ratio as sounding far away.
Top: Close sounds have a high direct-to-reverb ratio. Bottom: Far sounds have a low direct-to-reverb ratio.
Also, air absorbs high frequencies. The farther a sound source is from us, the more air the sound travels through, and so the less highs (treble) there is in the sound. Also, as a sound source becomes more distant and reverberant, it loses highs because the room surfaces (which create reverb) absorb highs more than lows.
Another depth cue is the direction that the sound reflections are coming from. Distant sounds create more audible reflections off the side walls, ceiling and floor than close sounds do.
Finally, a sound source becomes quieter as it moves away from you. That’s due to the inverse square law: the sound pressure level or SPL drops 6 dB for every doubling of distance.
Those facts suggest several ways to create depth in your mixes:
- Slightly turn down sounds that you want to be more distant, less “in your face”.
- Turn down the highs a little on the sound you want to be more distant. Cut a bit around 10 kHz.
- Turn up the reverb send more for distant sounds than for close sounds.
- Set the reverb send to Prefader rather than Postfader. Start with the track fader at 0, the reverb send to -15 dB or so, and the pre/post switch set to Pre. As you slowly turn down the track fader, the sound will become more distant. You are reducing the direct-to-reverb ratio. That’s a cue for the ears that the sound is becoming farther away.
- Set reverb predelay to 0 msec for distant sounds, or > 25 msec for close sounds.
- Mike close to get a close sound; mike farther away to get a distant sound. That’s a useful trick when you double vocals and you want them to appear at different distances from you.
- Record a sound source in stereo with two mics, and place the sound source far from the mics. Stereo gives a much more convincing illusion of depth than mono. That’s because stereo captures the directions that sound reflections are coming from.
Make it deep!
Bruce Bartlett is a microphone engineer (www.bartlettaudio.com), recording engineer, and audio journalist. His latest books are “Practical Recording Techniques 6th Ed.” and “Recording Music On Location.”
Originally posted 2011-07-31 23:45:46.