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Phase, in plain language.
Why multi-mic recordings lose punch, what phase coherence and time alignment each fix, and when to leave a recording's natural timing alone. Written for recording and mixing engineers.
Fix phase by source
- Drum phase alignment for multi-mic kits How to align drum microphones without flattening the kit. Check polarity, time delay, and frequency-dependent phase on close mics, overheads, and rooms.
- Bass DI and amp phase correction How to fix phase problems between a bass DI and a mic'd amp. Use delay, polarity, and all-pass phase correction to keep the low end full in the mix and in mono.
- Multi-mic guitar phase, electric and acoustic Two good mics on one guitar can sound worse than either alone. Whether it's a 57 and a ribbon on a cab or a pair on an acoustic, the capsule distance sets up a phase problem. Here is how to keep the tone and lose the hollowness.
- Aligning boom and lav for dialogue Boom and lav on the same actor should combine into one natural voice. Instead they often go hollow and phasey, and the problem moves as the actor moves. Here is how to align them, and how to divide moving material into regions where a fixed correction remains useful.
- Multi-mic podcast phase and bleed When two people record in the same room, each mic hears both voices, and the bleed sets up phase problems that hollow out your hosts — especially in mono, where most podcasts are heard. Here is how to keep the voices full.
- Phase coherence for live sound Multi-mic sources are just as phasey live as they are in the studio, but live you can't spend latency to fix them. Here is how phase coherence correction fits a live rig, and why time alignment is a different decision on stage.
Understand phase
- Phase coherence vs. time alignment Time alignment slides one mic to line up with another. Phase coherence is about how the mics add up across frequency. They fix different problems — here is how to tell which one you need.
- Why multi-mic recordings sound thin A single mic sounds full, but adding a second one shrinks the low end. Here is why related mics subtract instead of add, and how to tell phase apart from the other things that thin a sound out.
- What phase cancellation is Phase cancellation is what happens when two versions of the same sound combine slightly out of step and partly subtract. Here is the mechanism, from two sine waves up to a full multi-mic session.
- Comb filtering, and how to spot it Comb filtering is what phase cancellation looks like when one signal is a delayed copy of another: a row of evenly spaced notches across the spectrum. Here is what causes it, how the delay sets the spacing, and how to hear it.
- Phase vs. polarity Polarity is a flip of the whole waveform — the Ø button, every frequency at once. Phase is a time-and-frequency relationship between two signals. The Ø button only fixes one of them. Here is the difference and when each matters.
- When to preserve natural mic timing Not every phase difference is a problem to fix. The arrival-time differences between distant mics are often the depth and space you set them up to capture. Here is how to tell a useful timing difference from a harmful one.
- Phase rotation and all-pass filters An all-pass filter changes phase without changing level. It passes every frequency at the same volume but delays some more than others. Here is how that works, how it differs from EQ and delay, and why it changes a sum without changing a tone.
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