What is phase cancellation
When two signals share the same frequency but are out of phase (one is positive when the other is negative), they cancel each other out when summed to mono. The result: a hollow, thin sound in the low end when played on a single speaker.
How PRISM detects it
PRISM measures stereo correlation in the sub-bass range (20–120 Hz). A correlation below the genre threshold (0.50–0.60 depending on BPM profile) indicates potential mono cancellation. It also checks global stereo correlation as a secondary indicator.
The fix
Keep your sub-bass (below 120 Hz) strictly mono. Use a mid-side EQ or a stereo control plugin to mono the low end. Most bass elements should be centered — stereo information in the sub range almost always causes phase problems.
Check with a correlation meter. If you're consistently below +0.5, something in the low end is out of phase.
To fix this stereo problem, here are the tools PRISM producers reach for most — each picked for this specific case, not a generic list.