How do you handle phase issues when mixing or mastering audio tracks from different sources?

1 What are phase issues?

Phase is the relative position of a sound wave in time and space. When two sound waves are in phase, they have the same frequency, amplitude, and direction, and they add up to create a louder signal. When they are out of phase, they have opposite or different characteristics, and they cancel out or reduce each other. Phase issues can happen when you record the same sound source with multiple microphones, or when you combine tracks from different recordings or sessions.

2 How to identify phase issues?

One way to identify phase issues is to listen to your mix or master and pay attention to signs such as a thin or weak sound, lack of definition or separation between instruments or vocals, loss of stereo width or depth, and changes in tone or volume when switching between mono and stereo. Alternatively, a phase meter or correlation meter can be used as visual tools to show the phase relationship between two or more signals. A phase meter displays the degree of phase alignment with a needle that moves from left to right, while a correlation meter has a scale ranging from -1 to +1 indicating the degree of phase correlation. Positive values indicate that the signals are in phase, while negative values mean they are out of phase.

3 How to fix phase issues?

Adjusting the microphone placement or distance can help you avoid phase issues when recording the same sound source with multiple microphones. You should use the 3:1 rule, which states that the distance between two microphones should be at least three times the distance between the first microphone and the sound source.

Additionally, flipping the polarity or inverting the phase can help you correct phase issues when combining tracks from different recordings or sessions. Most audio software and hardware have a polarity or phase switch that allows you to reverse the direction of a signal. This can cancel out or reduce the phase difference between two signals.

For finer tuning, use a phase alignment or correction plugin to shift or align the phase of a signal, either automatically or manually. To compensate for time difference between two or more signals, make sure you use a time alignment or delay plugin to delay or advance the timing of a signal, either by samples or milliseconds.

4 How to prevent phase issues?

To avoid phase issues when recording, mixing, or mastering, it’s best to use the minimum number of microphones necessary to capture the sound source. Additionally, using the same type and model of microphones for the same sound source can help ensure that the microphones have similar frequency responses and polar patterns. It’s also important to use the same sample rate and bit depth for all your recordings and sessions. Checking your phase and correlation meters regularly and fixing any issues right away can save you time and trouble later on.