Mic Placement Basics: balancing proximity, gain staging, and room sound

Here are the two most powerful tools in an audio engineer's toolbox:

1. Microphone choice
2. Microphone placement

Microphones are sonic paintbrushes; the microphone significantly determines the sound of your track. Bright and harsh mics will always sound bright and harsh (which is why we don't make any ;-)

How you position the microphone is also incredibly important. That's why great engineers will say things like, "Before you reach for EQ, move the mic."

The Basics of Microphone Placement

As you move a microphone closer to a source:

• The mic’s signal level (output level) increases.
• The risk that the mic, preamp, or converter clips (overloads) increases.
• The risk of plosives during vocal recording increases.
• The mic's "sweet spot" gets smaller; if the source moves even slightly off-axis, you might hear a change in level or in frequency response.
• The amount of bass content in the track increases. (This is called “proximity effect.”)
• The relative level of ambient or room sound decreases.

Therefore if you want your track to sound less boomy or muddy, or you want a larger sweet spot so that the singer can move his or her head while singing without creating 4dB jumps in level, you could just move the mic farther away... except that that might create other problems. Expect these changes as you move a microphone farther away from a source:

• The mic's signal level decreases; for quiet sources, you might need so much preamp gain that the track becomes noisy.
• The mic loses proximity effect. Bright mics will sound thin and harsh.
• The mic will hear more ambient / room sound. In rooms with insufficient acoustic treatment, this effect is similar to reverb, although it probably will not sound good. 

Balancing Gain, Proximity, and Room Sound

Getting great results during tracking requires managing all of these factors: the volume of the source, the amount of echo/reverb in the room, the quality of the signal path, etc.

For example, consider mic placement for vocal recording. If the recording sounds too intimate, or has too much bass, or if the singer has problems with plosives, move the mic farther away.

However, if the room is untreated, moving the mic farther away will increase the relative level of reflected sound. If you need a drier, less ambient sound, then you have no choice but to keep the microphone close to the source, or record in a less-reflective space.

To reduce reflections, place gobos or acoustic absorption materials behind and around the mic and the singer. This is not a small tip. Every great tracking room in history had expertly placed acoustic treatment, whether absorption or diffusion. Most bedroom studios need acoustic treatment more than they need more microphones or preamps.

Successful tracking requires experimentation with mic position. We recommend auditioning all mic placements before the session begins. The payoff comes at mix time, when you find that you need little to no EQ or other processing to make the tracks do what you need.