Riverflux Audio · Practical · Mid/side + mono fold
Mid/side processing vs stereo phase rotation for mono compatibility
Same mono fold. Two different jobs. Mid/side (M/S) changes how much Mid versus Side you keep. Continuous stereo phase rotation repairs leftover L/R band fights that still cancel when you sum. Do not swap the tools.
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PHIXER is free stereo phase-repair (VST3/CLAP/AU · Win/Mac/Linux) from Riverflux Audio. Continuous, frequency-aware phase rotation for leftover stereo beds. It is not an M/S encoder, not a width imager, not a 180° polarity button, and not a sample-align delay. Use M/S for width balance. Use polarity and timing first. Reach for PHIXER only if a stereo path still hollows a band on true mono fold.
Quick map
| Tool | What it changes | Mono fold risk |
|---|---|---|
| M/S encode / decode | How much shared Mid vs difference Side you keep or EQ | Boost Side (or cut Mid) and mono can thin body, kick, or vocal center |
| Stereo width / imager | Often Side gain or Haas-style tricks under the hood | Same mono risk when Side dominates |
| Polarity (Ø) | Whole-waveform 180° flip on one path | First fix when L and R fight everywhere |
| Timing / sample align | Delay so attacks agree | Fixes mic distance and layered one-shot offsets |
| Continuous phase rotation (PHIXER) | Spectral L/R phase relationship without collapsing to Mid-only | Last resort when Ø + timing fixed only part of the spectrum |
When M/S helps mono compatibility
- Protect Mid lows. Keep kick / bass / lead vocal mostly Mid. High-pass Side so mono still carries weight.
- Undo a width binge. If a prior M/S or imager made Side too loud, pull Side down or restore Mid before you touch phase tools.
- EQ Side air, not Mid body. Brighten Side; leave Mid foundation alone when phone / club fold matters.
- Check after every M/S move. True mono listen. Correlation near 0 after a Side boost is a hint, not a verdict. Ears on fold win.
When stereo phase rotation helps
- Stereo bed still cancels a band after Mid is protected and Side is sane.
- Polarity flip helped some ranges but not others (classic continuous L/R fight).
- Timing nudge already lined attacks and mono still hollows midrange or low-mids on fold.
- You must keep the stereo image. Collapsing to Mid-only would fix mono but kill the arrangement.
PHIXER role (honest)
- True mono fold. Sum L+R (or invert-null). Do not mute one side and call it mono.
- Name the hole. Bass body, kick punch, vocal center, or a whole stereo pad.
- M/S hygiene first. If Side is oversized, fix width / Mid-Side balance before phase toys.
- Polarity then timing. Flip Ø. Nudge samples or ms. Re-null. Full flow: Null test + polarity checklist.
- Read correlation as a hint. Quick card: +1 / 0 / -1 in 60 seconds.
- PHIXER only if the path must stay stereo and a band still cancels on phone / club / LoRo fold.
- Prove it. Mono A/B. If the null did not improve, undo. See When not to use PHIXER.
Do not confuse the jobs
- M/S is a balance / EQ domain (Mid vs Side).
- Imagers often sell width; they do not repair spectral L/R fights.
- Time-align slides delay. Different job from continuous rotation.
- PHIXER rotates leftover stereo phase. Free. Not a replacement for M/S discipline.
Related guides
- Stereo imager vs phase repair
- Polarity invert vs continuous phase rotation
- Correlation meter quick-read (+1 / 0 / -1)
- Null test + polarity checklist
- When not to use PHIXER
- Mid/Side vs phase repair (earlier cluster page)
- PHIXER for Bus Sidechain / heavy bus compression and sidechain stereo phase
- Hub · Product
- Haas delay width tricks vs true phase issues