Aligning boom and lav for dialogue
By Thomas Dulin Published
Boom and lav are the two halves of a dialogue recording. The boom has the natural tone and the perspective of the scene. The lav has presence and consistency, and it keeps working when the boom can’t get close. Editors cut between them and blend them constantly — and the blend is where phase turns a clean voice hollow.
Why dialogue phase is its own problem
The boom and lav pick up the same voice from very different distances, so the boom arrives noticeably later. Summed, they comb filter the voice, thinning it and adding that phasey, slightly boxy quality that pulls a listener out of the scene.
Dialogue adds a twist the music sources don’t have: the actor moves. As they turn or cross the room, the boom-to-source distance changes take by take and even within a line, so the offset between boom and lav isn’t fixed. The comb filter moves with the performance.
Fixed shots
When the performer holds still, this is a static problem. Choose a reference — usually the lav, since it’s the consistent, present track — flip polarity if the two are inverted, and align the boom to the lav with a single offset. One correction holds for the whole shot.
Moving performers
When the distance drifts, a single fixed offset can only be right for one moment of the take. Break the work into shorter regions whose timing relationship stays stable, analyze a representative passage in each region, and recheck transitions. If the offset keeps changing within a region, correct the underlying timing in the DAW before using PhaseLock for the phase relationship.
Audio demo to add: boom and lav on a moving performer, summed untreated then aligned with PhaseLock — same take, level-matched, with a short methods note.
Check it where it plays
Fold to mono and listen for intelligibility and body, since broadcast and a lot of playback is mono. Keep some of the boom’s sense of the room — the goal is one believable voice in a space, not a lav so tightly locked that the scene sounds dead. Correct the hollowness; keep the perspective.