Kick in/out mic phase — why beater + resonant cancel sub in mono
You miked the beater for click and the resonant head (or “out”) for body. In headphones the kick feels huge. Flip the drum bus to mono — sub thins, the thud hollows, or the click sits on air. That’s kick in/out phase, not a missing 808 or a weak compressor.
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PHIXER is free stereo phase-repair (VST3/CLAP/AU · Win/Mac/Linux) from Riverflux Audio. Frequency-aware phase rotation for L/R and dual-path fights — not a polarity button, not a sample-nudger, not a widener. On kick in/out, use only after polarity and mic distance timing are honest — skip when you deliberately split click vs body with intentional phase.
What kick in/out phase fights sound like
Two close mics on a kick rarely arrive in perfect phase across the whole spectrum. The beater mic loves attack and upper mid punch; the resonant / port / “out” mic loves low thump. Blend them, and mono summing reveals cancellations headphones hide — same class of problem as snare top/bottom and bass that disappears in mono.
Classic symptoms:
- Sub disappears in mono — fat in headphones; thin or clicky on a phone, club PA, or Instagram mono modes.
- Body hollows when both mics are up — each mic solo sounds fine; the blend cancels the thud band.
- Polarity flip “fixes” then ruins click — one Ø setting restores weight but kills attack (or the reverse). That’s a hint the fight is frequency-dependent, not a single 180° mismatch.
- Overheads make it worse — OH/room spill adds another path that fights the close pair. See overhead & room mic phase.
Why beater + resonant fight (and why that’s normal)
Sound leaves the batter head, travels through the shell and port, and hits each capsule at a different distance and angle. Low frequencies have long wavelengths; a few centimeters of path difference still matter at the thud and sub. Capsules and preamps can also flip absolute polarity relative to each other. None of that means you miked “wrong” — dual-path kick is a feature; phase fights are the tax. Name what disappeared (sub, thud, click, beater) before more saturation, another sample layer, or an imager.
Why mono reveals them
In stereo (or a hard-panned fake “wide” kick), opposing-phase energy can still reach each ear. Sum L+R — phones, laptop mixes, club systems that mono the low end — and those bands cancel. Kick lives where mono is least forgiving. Check: beater solo → resonant solo → blend in stereo → blend in mono. If the blend collapses, fix the pair before the master. Workflow: mono-check before/after.
Honest order of fixes
1. Polarity first (Ø / Invert)
Hard 0° / 180° on one mic vs the other. Free and often enough. Flip the resonant under the beater (or the reverse); listen in mono. Keep what restores weight without wrecking click. If one flip fixes it, stop. More: polarity invert vs phase rotation.
2. Time-align when path length is the culprit
If waveforms show a clear lag at the transient, nudge the later mic (or add a few samples of delay) so attacks line up enough that mono stops cancelling sub. Over-aligning into identical spikes can kill the dual-mic character — align for mono safety, leave musical shell resonance alone. Details: phase repair vs time-align.
3. Frequency-aware phase rotation (PHIXER) when leftovers remain
After polarity and a reasonable align, some kick pairs still fight by band — sub dies in mono while click survives, or thud thins while beater stays sharp. That’s when spectral phase rotation helps: PHIXER rotates phase by frequency so more energy survives mono. It does not invent missing low end, replace a better mic move, or “fix” intentional click/body splits.
Decision table
| You notice… | First try | Why |
|---|---|---|
| Invert one mic and sub/thud returns | Polarity — done | Simple 180° mismatch between capsules/paths |
| One transient clearly late vs the other | Time-align / nudge | Mic distance / path delay |
| Align + polarity help some bands; others still die in mono | PHIXER on the stereo kick group or printed stereo pair | Frequency-dependent residual fight |
| A mic sounds bad even solo | Move mic / swap capsule / EQ the take | Phase tools won’t fix a weak capture |
| Mono is fine; you just want “wider” kick | Confirm mono first, then width carefully | Imagers ≠ phase repair |
| You want intentional phase for click vs body split | Don’t “repair” — own the tradeoff | Intentional phase as tone control |
When frequency-aware phase repair helps on kick in/out
- You’ve polarity-checked both mics, roughly aligned the attack, and a band (often sub or low thud) still collapses in mono.
- You printed a stereo kick stem (L/R beater/resonant, or a processed stereo bounce) and that stereo file itself fights.
- Beater + resonant pass a headphone test but fail mono after basic alignment — same physics as dual-mic bass/guitar.
- Individual mics sound fine solo; only the blend cancels.
PHIXER belongs on residual dual-path / stereo fights — not as the first plugin on every kick channel.
When NOT to use PHIXER on kick in/out
- Single mono kick mic — no dual-path phase to repair. Thin tone is mic placement, tuning, or EQ.
- Clear polarity only — if Ø on the resonant restores mono sub, stop. See polarity vs phase.
- Clear timing offset only — a mic a few samples late is nudge/delay, not rotation. See vs time-align.
- Intentional phase for click/body split — some engineers leave a slight fight so click stays sharp while body stays short. Own that tradeoff; don’t “repair” it into lifeless mono perfection. Honest list: when not to use PHIXER.
- Using a stereo imager to “fix” cancellation — width tools don’t restore cancelled sub. See PHIXER vs imagers.
- Replacing a missing sample layer — if you wanted an 808 under the kick, that’s arrangement, not phase repair. Sample stacks: layered one-shots.
Short practical checklist
- Solo beater. Solo resonant. Listen for tone problems that aren’t phase.
- Blend both. Flip to mono. Note sub / thud / click / beater.
- Try polarity on one mic. Keep the best combo.
- If one attack is late, nudge timing; re-check mono.
- If a band still cancels on the stereo / dual-path blend, try PHIXER — then mono-check again.
- Only after mono is solid (or you consciously accept intentional phase), touch saturation, parallel compression, or width. Imagers last.
- Then check how the fixed kick sits under overheads and the rest of the kit — don’t fix the master first and ignore the drum group.
Order of operations: mic placement → polarity → time-align → frequency-aware phase repair → creative width / parallel. Skipping to an imager or “another kick sample” on a cancelling in/out pair is how hollow mono drum mixes ship to phones and club PAs.
Related reading
- Snare top/bottom mic phase — sibling dual-path drum fight
- Overhead & room mic phase — OH spill vs close mics
- Sample stacks & layered one-shots — when you add kick samples under the miked kick
- DI + mic / dual-mic phase — same dual-path logic on bass/guitar
- Why bass disappears in mono — mono-sum physics on low end
- Phase repair vs time-align — nudge first when attacks are late
- Polarity invert vs phase rotation — 180° first
- When not to use PHIXER · Product · Hub
Get the free fixer
PHIXER — free stereo phase-repair from Riverflux Audio (VST3/CLAP/AU · Win/Mac/Linux). No invented stats: try it on your beater + resonant pair after the checklist above.