Sound II Reading

2.4. Phase

In the realms of audio recording and mixing, there are few words that appear more frequently than ‘phase’. In short, the implications of phase impact on almost every decision and action we take as a sound engineer. Whether it’s determining the placement of microphones, our perception of stereo, the application of EQ or the sweep of a synthesizer’s filter, all of these processes have some effect on phase.

One factor that can induce phase problems is the orientation of the microphones. A common occurrence of this comes from the mic’ing a snare with microphones placed on the top and bottom of the snare. Because the microphones are approaching the snare from opposite directions, the compressions and rarefactions picked up by each microphone will be correspondingly inverse; as the top mic moves into positive, the bottom mic moves into negative. When the two mics are combined, the resulting sound is weaker, as a number of harmonics in the snare are canceled out. By reversing the phase of the bottom mic the problem is eliminated.

Seeing phase as purely problematic is seeing only half the picture, though; there are many situations in which manipulating or distorting phase can have a positive impact on the recording process. It is widely known, for example, that the process of equalization, as well as modifying the relative timbral balance of a signal, also creates differing phase shifts in the frequency spectra. Although this phase distortion might seem problematic at first, it remains a defining quality of the sound we associate with specific EQ's. Many of the vintage EQ's that today's plug-ins emulate are highly sought after for their sound. Analog Moog and Oberheim filters are so revered, largely because of the phase distortions they impose on a filtered oscillator. Effects such as flangers or phasers also make deliberate use of phase manipulation to modify the timbre of a sound.