PHIXER for Bus Sidechain: heavy bus compression / sidechain and stereo phase
Heavy bus compression and sidechain ducking can shift the stereo image and expose phase fights. A kicked pad bus that feels huge in headphones can hollow on phone, Bluetooth, club PA mono, or livestream fold. Sidechain gain reduction is not the same job as stereo phase repair. Polarity, latency, attack timing, and true mono listen come first. Free PHIXER helps after residual L/R fights remain on a stereo bus bed you must keep stereo.
Download PHIXER free YouTube tutorial YouTube intro
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 sidechain compressor, not an envelope follower, not a stereo imager, and not a substitute for bus gain structure or mono audition after ducking. Use it after hygiene, when residual spectral cancellation remains on a stereo bus you must keep stereo.
Why heavy bus compression / sidechain moves the image
- Kick sidechain duck on a stereo bus. Pad, bass, or synth bus pumps in cans; mono fold hollows the middle when L/R already fight. Polarity and timing first; spectral tools last.
- Heavy bus compression next to width tools. Group crush plus a stereo imager can shift Side energy while the compressor links L/R unevenly. Cousin: Stereo imager vs phase.
- Sidechain next to mid/side balance. Mid/side moves and continuous phase rotation are different jobs. Cousin: Mid/side vs stereo phase rotation.
- Polarity still comes before rotation. Flip Ø on one path before chasing continuous phase. Cousin: Polarity invert vs continuous phase rotation.
Fast mono fold check with PHIXER (about 60 seconds)
- Solo the ducked or heavily compressed bus. Sum L+R with a monitor controller or utility. Do not mute one side to "hear the problem."
- A/B stereo vs mono across a sustained soft source and a kick hit. Note what disappears: kick body, bass weight, pad mid, vocal chest.
- Bypass the sidechain key briefly. If mono weight returns, the duck depth / release / stereo link settings may be the scoop, not free stereo. Then check Ø and a few samples of attack timing on L vs R.
- Confirm on a phone speaker, then again after imagers, mid/side moves, or parallel crush join the bus. Re-check after stems combine.
Honest order of fixes (before spectral phase rotation)
1. True mono listen after the duck / crush
Hard L+R sum with both ears open on the bus or stem sum. Habit: mono check workflow.
2. Sidechain depth, release, and stereo link
If mono scoops only when the key is deep and release is long, fix the duck first. Linked stereo compression often behaves better than dual-mono links that fight each other.
3. Polarity before more processing
Flip Ø on one bus path or one side while mono. Keep the flip that returns body. Guide: polarity invert vs continuous phase rotation.
4. Attack timing before spectral tools
Nudge a few samples or ms so transient peaks agree across L and R of the ducked bus. Often enough on phones and club fold.
5. Width / imager before spectral tools
Mute the stereo imager or Side boost briefly. If mono weight returns, fix width first. Cousin: Stereo imager vs phase.
6. Mid/side hygiene before continuous rotation
Protect Mid lows. High-pass Side. Reach for continuous phase only if fold still thins a band. Cousin: Mid/side vs phase rotation.
7. Skip when intentional thin mono is the point
Some Side-heavy ducked beds are meant to stay edge-only in mono. Honesty list: When not to use PHIXER.
8. Only then audition residual L/R spectral fights
If the stereo bus 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. Watch the YouTube tutorial and the YouTube intro.
Bus / sidechain setups and common mono failures
| Setup | Common mono failure | First fix |
|---|---|---|
| Kick key into pad / synth bus | Pad mid scoops on phone fold | Mono listen; check stereo link and Ø |
| Kick key into bass bus | Bass weight dips under the duck | Depth / release; polarity; timing |
| Heavy group bus compressor | Body thins when L/R already fight | True mono; Ø; less width |
| Bus crush + stereo imager | Side boost cancels on fold | Imager vs phase |
| Sidechain + mid/side balance | Side gain mistaken for phase fight | M/S vs rotation |
| Ducked bus into master | Streaming / phone fold thins | Mono check master; less Side |
Related guides
- PHIXER for Multiband / crossover phase shifts and mono check
- Stereo imager vs phase repair
- Polarity invert vs continuous phase rotation
- Mid/side processing vs stereo phase rotation
- PHIXER for Stems / stem-bus phase
- PHIXER for Parallel Bus
- Parallel compression / bus phase
- When not to use PHIXER
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- Product