EQ boosts on multimiked tracks change comb-filtering relationships unpredictably; cuts are safer

Every minimum-phase EQ filter shifts the phase of the processed signal, most severely at the filter’s center frequency. In a multimiked recording (e.g., close mic + room mic), EQ applied to one mic changes its phase relationship with the others, altering the comb-filtering character of the combined sound. A boost increases the level of the boosted frequency while shifting its phase, potentially worsening comb-filtering artifacts. A cut reduces the problematic frequency while concentrating phase shifts in regions that matter less. Therefore, EQ cuts are lower-risk than boosts in multimiked contexts.

Examples

Boosting 2 kHz on a snare close mic while a room mic also captures 2 kHz comb-filters that region erratically. Cutting 2 kHz on the close mic reduces the comb-filtering contribution at that frequency instead.

Assessment

Explain why EQ boosts are more problematic than cuts in a multimiked recording. Describe what ‘phase response’ has to do with this.