Tom multi-mic phase: why fills go hollow
A rack tom, floor tom, and overheads all hear the same hit at different distances. Solo the fill and it punches. Sum to mono (or collapse the kit bus) and the body thins. That is usually polarity and arrival timing first, residual stereo fights second.
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PHIXER is free stereo phase-repair (VST3/CLAP/AU · Win/Mac/Linux). Frequency-aware phase rotation for leftover L/R fights. It is not a mic time-aligner and not a polarity flip. Use it after Ø and delay hygiene on multi-mic drums.
What actually cancels on tom fills
- Close tom vs overhead. Same strike, different path length. Comb notches move as you ride fills.
- Floor tom vs kick spill. Low energy shared across capsules. Wrong polarity sucks chest out of both.
- Stereo OH pair vs close mono spots. The fill is wide in headphones, hollow on a mono fold or club PA.
- Room mics under the kit bus. Adding “air” without mono-checking the sum.
Related drum guides: snare top/bottom, overhead & room, kick in/out.
Hygiene before any phase rotator
| Step | What to check | Goal |
|---|---|---|
| 1. Polarity (Ø) | Each close tom vs OH; floor vs kick | Max low-mid when both are up |
| 2. Time align | Align closes to the OH (or OH to kick, stay consistent) | Attack lands together |
| 3. Mono-check kit bus | Flip mono while playing the fill | Catch hollow before FX |
| 4. Correlation glance | Kit bus meter during the fill | See if sum is fighting |
| 5. PHIXER last | Only if a stereo print still cancels by band | Residual spectral repair |
Meter deep dive: correlation & phase meters. Workflow: null-test + mono-check.
Practical fill checklist
Solo the fill, not just the tom track
Audition the whole kit bus (closes + OH + rooms). Phase problems show up in the sum.
One reference path
Pick overheads (or kick) as the timing reference and stick to it for the session. Random per-tom aligns create new combs.
Gate after polarity
Tight gates on mis-polarized toms hide the problem until you open the fill. Fix Ø first.
Stereo bus last
If the printed stereo kit still dips in mono after hygiene, try frequency-aware phase rotation on that stereo bus, then mono-check again.
When NOT to reach for PHIXER
- You have not flipped polarity on close vs OH yet.
- Closes are still tens of milliseconds late vs the reference.
- You want PHIXER to “widen” the toms. Wrong job.
- The source is a mono tom sample with no stereo fight.
Quick path: Mono-check the fill → Ø close toms vs OH → align to one reference → re-check mono → PHIXER only on residual stereo cancellation → mono-check again.