Phase Correlation Checker

What is phase correlation?

Phase correlation measures the relationship between the left and right channels of a stereo audio signal. A correlation of +1 means the channels are perfectly in phase (identical signal — mono). A correlation of 0 means the channels are unrelated. A correlation of −1 means the channels are perfectly out of phase (polarity inverted) — when summed to mono, they cancel completely and the audio disappears. Our free phase correlation checker reads your file and reports the average correlation, mono compatibility, and whether your low end has phase issues that could cause bass to vanish on mono playback systems.

Why mono compatibility matters

Many listeners hear your music in mono: phone speakers, Bluetooth speakers, smart speakers (Alexa, Google Home), club sound systems, and many PA systems all sum stereo to mono. If your mix has phase issues — typically from stereo widener plugins, room microphones, or misaligned multi-mic recordings — summing to mono causes cancellation. Bass disappears, vocals thin out, and the mix loses power. A phase check before release catches this. Aim for a correlation above +0.5 across the whole track and above +0.8 in the low end (below 200 Hz) where cancellation is most destructive.

How to read a phase correlation meter

Common causes of phase problems

Phase issues typically come from: (1) Stereo widener plugins that use delay or all-pass filters to create width — these can push correlation negative. (2) Multi-mic recordings where mics at different distances capture the same source at slightly different times — the Haas effect. (3) Parallel processing where one path has latency the other doesn't. (4) Polarity flips from cables, preamps, or plugins that invert phase. (5) M/S processing with too much side channel energy in the low end. A phase check identifies which of these is affecting your mix.

How to fix phase issues

If your phase correlation is below +0.5 or goes negative: (1) Check if a stereo widener plugin is on the master bus — bypass it and re-check. (2) Sum your low end (below 200 Hz) to mono using a mid-side EQ or a crossover — bass should always be mono. (3) Time-align multi-mic recordings by zooming in on transients and adjusting track delay. (4) Check polarity — flip the phase of one channel and see if correlation improves. (5) Avoid using width plugins on the master bus; use them on individual elements instead. Always check phase after any stereo processing, not just at the end.