Film and TV LoRo fold-down: keep stereo stems alive in mono
Your trailer bed and FX stems sound huge in stereo headphones. On a LoRo fold, TV mono path, or hotel-room speaker, bass thins, impacts hollow, and music beds lose weight under dialogue. That is fold-down physics, not a broken limiter.
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PHIXER is free stereo phase-repair (VST3/CLAP/AU · Win/Mac/Linux) from Riverflux Audio. Frequency-aware phase rotation for leftover L/R fights on stereo material. It is not a loudness processor, not an LtRt encoder, and not a substitute for polarity, timing, or a real mono/LoRo check. Use it after hygiene, when residual spectral cancellation remains.
What fold-down failure sounds like
- Trailer boom thins under VO. Wide low-end bed cancels when summed.
- Impact stacks lose punch. Layered hits / printed FX cancel body (same idea as sample stacks).
- Music bed hollows on hotel TV. Side-heavy imaging collapses into a weaker mid.
- Hard L/R FX disappear. Extreme panning or anti-correlated stereo prints fold poorly.
- "Fine in the suite, dead on delivery". Nearfields forgave correlation problems the fold reveals.
LoRo vs "just hit mono"
LoRo (Left only / Right only) fold is a straightforward stereo sum path used in many broadcast and consumer contexts. It is not the same as a full matrixed LtRt / surround downmix, but it still exposes anti-correlation. If L and R fight by band, the fold loses energy. Social and YouTube have a related problem (YouTube / social mono fold checklist). Live matrices show it too (FOH / foldback / stream).
Pre-delivery checklist
1. True mono / LoRo listen
Sum L+R (or your facility LoRo monitor path). Listen under dialogue and alone. Full habit: mono check workflow and null-test + mono-check.
2. Polarity and timing on dual paths
DI+mic prints, dual-mic FX, parallel buses, layered impacts: flip Ø, then nudge delay before you reach for EQ or width.
3. Temper imagers and Mid-Side extremes
If correlation tanks when width engages, that width costs the fold. Compare PHIXER vs stereo imagers and Mid/Side vs phase repair.
4. Check beds under dialogue
Music and FX beds often pass alone then die under VO. Fold with dialogue present.
5. PHIXER on residual stereo fights
After hygiene, if a stereo stem or print still cancels by band on LoRo/mono, try frequency-aware phase rotation, then re-check the fold. Skip pure mono dialogue stems.
6. Re-check the delivery print
Bounce the format you deliver and fold that file. Encoding and stem consolidation can reveal problems the session hid.
Decision table
| You notice… | First try | Why |
|---|---|---|
| Bass / boom gone on LoRo | Ø / timing / less side bass | Wide or dual-path low end |
| Impacts / stacks hollow | Align layers / reduce stack | Near-copy cancellation |
| Widener hurts the fold | Bypass or reduce imager | Side energy, not repair |
| Still band-cancels after hygiene | PHIXER on stereo stem/print | Residual spectral L/R fight |
| Mono dialogue dull alone | Tone / mic / processing | Not an L/R phase job |
Post-specific tips
- Trailers and promos. Assume phone, TV mono, and aggressive fold. Keep boom and hook correlated.
- Broadcast music beds. Stereo beds under VO: fold with dialogue, not only solo.
- Printed FX libraries. Stereo prints you did not mic yourself still cancel. Treat them like stacked samples.
- Stem deliveries. Fold each music/FX stem and the full mix. A good full mix can hide a bad stem.
- Read meters honestly. Correlation & phase meters help, but ears on a real fold win.
When frequency-aware phase repair helps
- You already LoRo/mono-checked, fixed polarity/timing, and tempered width tools, but bands still cancel.
- Printed stereo stems (music, FX, parallel buses) still fight in the delivery fold.
- A final stereo print shows residual L/R cancellation after the checklist.
PHIXER does not replace a broadcast chain, invent missing arrangement energy, or encode surround. It is residual stereo repair for post workflows that already did the fold homework.
When NOT to use PHIXER
- You have not folded yet. Do LoRo/mono first.
- Clear polarity / delay / imager fix. Stop when the fold is solid.
- Mono dialogue stem alone. No L/R to repair.
- Using PHIXER to "pass loudness". Wrong job.
- Confusing LoRo with a full surround downmix problem. Fix stereo correlation first; matrix issues are a separate discipline.
Quick path: LoRo/mono listen → polarity & timing → pull back width → PHIXER only on leftover stereo fights → re-fold the delivery print.