Bluegrass / acoustic string-band multi-mic phase: closes vs shared OH and room fold
Close mics on banjo, mandolin, fiddle, guitar, and bass feel rich in the booth and on stage wedges. On festival boards, livestreams, or phone speakers, midrange and pick attack often thin or cancel against shared OH and room that carry the same band a few milliseconds later. That is usually polarity and arrival time between instrument closes and OH/room paths, plus a stereo bed that was never folded before send. Fix polarity and small delays first. Frequency-aware phase repair belongs only after residual L/R fights remain on stereo beds before mono fold.
Download PHIXER free PHIXER hub
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 bluegrass compressor, not a widener, and not a substitute for mic placement or mono audition of the festival or stream bus. Polarity and timing first; PHIXER after residual spectral fights.
What bluegrass / string-band phase failure sounds like
- Midrange and pick attack thin on livestream. Closes and shared OH share the same energy a few ms apart.
- Banjo / mandolin huge in booth, hollow on phone. Hard L/R instrument layouts disappear when the platform folds.
- Fiddle and guitar fight shared room. Same content twice with different delay into the matrix.
- Bass body cancels against festival OH. Stereo bed never checked in mono before board send.
- Fine in cans / wedges, broken for remote viewers. Same destinations as live FOH / foldback, OBS livestream, YouTube / social.
Fast mono audition (about 60 seconds)
- Solo the festival / stream / mix bus (not only booth headphones or wedges). Flip a utility to mono.
- A/B instrument closes muted vs open under OH/room. Note what disappears: midrange, pick attack, bass body, fiddle bite.
- Solo pairs: banjo vs OH, mandolin vs room, guitar vs shared OH, stereo bed vs mono fold.
- Check correlation on the delivery bus, then with closes muted vs full.
Order of operations (before spectral phase rotation)
1. Polarity between instrument closes and shared OH / room
Flip closes vs OH, or section instruments vs room, when midrange or bass body returns immediately. Guide: polarity vs phase. Related: acoustic guitar, string section.
2. Small delay align closes to the OH / room image
Instrument closes often arrive earlier than shared OH or room. A few samples of delay on closes (or nudge to the hero OH image) often restores midrange better than any widener.
3. One hero band image to the festival or stream bus
Do not send every close and OH path all hot into the livestream or festival matrix. Pick a hero image (often balanced stereo OH or a focused band bed), keep extras muted or low. Parallel stacks are classic hollow-mid on phone fold. Related: piano stereo.
4. Prefer hero OH/room as the body; quieter color closes
Closes should color pick attack and instrument detail, not replace the hero image for the stream mix. If every close sits at full level under loud OH, mono fold almost always hollows midrange. Pull closes first.
5. Skip wideners and Haas on string beds before fold
Short-delay width and stereo imagers make booth headphones huge and phones hollow. Keep critical midrange and bass centered for festival and stream.
6. Only then audition residual L/R spectral fights
If a stereo band bed must stay stereo and fold still hollows a band after the steps above, gentle frequency-aware phase rotation can help. Prove it with mono A/B, rotator bypassed vs engaged.
Path types and typical failure modes
| Path | Common mono failure | First fix |
|---|---|---|
| Banjo/mandolin closes + OH | Midrange / pick attack cancel on stream | Polarity; delay closes; quieter closes |
| Fiddle + shared room | Bite disappears on phone | Polarity + delay; hero image |
| Guitar + festival OH | Body combs under board | Bleed control; polarity; one hero |
| Bass close + OH | Low end thins on PA fold | Polarity; delay; center lows |
| Stereo band pair hard L/R | Huge in cans, gone on phone | Center critical mids; simplify width |
| FOH / matrix → OBS / YouTube | Fine in booth, hollow for viewers | OBS / YouTube |
Festival / livestream checklist (to send)
1. Label closes vs OH vs room paths
Name banjo, mandolin, fiddle, guitar, bass closes, shared OH, and room so operators know what hits the livestream or festival board. Ambiguous stacks get left open and comb on fold.
2. Mono-check delivery bus alone, then with full band
Solo midrange and pick attack in mono. Then open bass and fiddle in mono. Note fights between close color and hero body.
3. Watch phone and social destinations
Most remote viewers hear mono or near-mono. Guides: YouTube / social, live FOH.
4. Optional null / mono workflow before set
Host-agnostic habit before you go live or print: master bus mono checklist.
When PHIXER belongs on string-band stereo
- The material is already stereo and must stay stereo (stereo OH pair, stereo band bed), not a mono close you fake-widened.
- Polarity, delay align, and hero-path levels are cleaned up, but fold still hollows a band of the spectrum.
- You can A/B mono with the plugin bypassed and hear clearer midrange or attack without wrecking the image.
- You are not using it to "fix" unaligned closes+OH under festival room, or to replace a time-align edit on the matrix.
Decision table
| You notice… | First try | Why |
|---|---|---|
| Midrange thins when OH opens under closes | Polarity; delay closes; quieter closes | Arrival-time fight |
| Banjo + room collapse on stream | Hero image; polarity; delay | Stacked identical content |
| Fine in booth, thin on phone | Mono delivery bus; pull closes | Booth ≠ viewer fold |
| Stereo bed still cancels by band | PHIXER on that stereo bed | Residual spectral L/R fight |
| Mono instrument alone is dull | Tone / EQ / gain / mic choice | Not an L/R repair job |
When NOT to use PHIXER here
- You have not mono-auditioned the festival / stream / mix bus yet.
- The fix is obviously polarity, delay, one hero band image, or quieter closes under OH/room.
- You want PHIXER to make the band louder, wider, or "more bluegrass." Wrong job.
- The path is mono and the print problem is balance or EQ.
- See also when not to use PHIXER.
Quick path: Solo delivery bus in mono → polarity closes vs OH/room → delay-align closes → one hero band image → quieter closes under hero → skip Haas/imagers → mono-check with full band → PHIXER only for leftover stereo cancellation on a string bed → fold again for festival / stream / phone.