1 · What DeltaWidth is
DeltaWidth is a stereo-width plugin built on the Delta family thesis: see what it does, and measure the cost. It does two things — it generates believable stereo from a narrow or mono source, and it sculpts the width you already have — and it draws the one thing every other widener hides: how much of your signal cancels in mono, band by band.
The design line is deliberate and worth stating up front: DeltaWidth answers “was this recorded wide?” — never “is this in a room?” It models the small differences between two microphones capturing the same direct sound. Room, reflections and reverb are a different tool’s job. Keeping them out is exactly what lets the width stay clean and mono-safe.
The truthful promise is not “mono-safe width at no cost” — that’s the lie every widener tells. Decorrelation always trades mono-compatibility for space. DeltaWidth’s job is to show you that trade and hand you the meter.
2 · Install & activate
DeltaWidth is in development — the fourth Delta product, planned after DeltaMeter, DeltaEQ and DeltaComp reach the market. When it ships it installs the way the rest of the family does: a single installer drops the VST3 · AU · CLAP and a Standalone, and one machine-bound license activates it. This manual is a draft that will track the beta build.
3 · Signal flow: two stages
The signal runs through two stages in series:
INPUT → [ 1 · GENERATE ] → [ 2 · SCULPT ] → OUTPUT
GENERATE creates width where there was little or none. SCULPT shapes the width you have — including whatever GENERATE just added. The Butterfly / WIDTH view sits across both: it shows the source width (a ghost), the live width, and the mono-loss (a danger mask), and it is also the surface you edit on. The OUT control trims final level.
4 · Stage 1 — Generate
GENERATE builds stereo by octave-band quadrature decorrelation. The signal is split into octave bands; in each band a Side signal is derived from a 90°-shifted (Hilbert) Mid, with the sign alternating per octave to build a big, stable image. The key property is what makes it honest:
L = Mid + Side, R = Mid − Side → L + R = 2·Mid
Because Side is derived from Mid, the mono sum cancels Side cleanly back to the original Mid. No comb-filtering, no hollow swoosh — mono loses the space but never the tone. Most delay-based (Haas) wideners break this destructively; this one doesn’t.
Stage 1 is deliberately octave-stepped and stays that way. Coarse bands are precisely why generated width sounds solid; narrow decorrelation bands smear the image instead of building it. Finer resolution belongs to Stage 2 — see §10.
Honest status: GENERATE works and null-tests clean, but has not yet been ear-tested through real program material. Treat it as a capable prototype until that listening pass is done — it is the gating item before this stage is called “finished”.
5 · The width curve
You don’t set width with a single knob — you draw a width-amount curve across the spectrum. The GEN control sets the overall amount; LF and HF tilt it low and high around a PIVOT frequency. The natural, honest shape is: lows pinned toward mono, mids moderate, highs open — width where the ear expects it and mono-safety where it matters. Think of it as an EQ, but for dimension instead of level.
HARM (the Side-harmonic generator) adds a subtle, band-limited saturation that lives only in the Side — new air and sheen that weren’t in the source. It’s honest by construction: Side-only harmonics vanish in mono, so they add no new mono artifacts. Keep it subtle; it’s the easy one to overdo, and it shows in the delta readout.
6 · Stage 2 — Sculpt
SCULPT turns the Butterfly view into an instrument — the DeltaEQ-ghost move, applied to width. Grab a width band on the wings and drag to widen or narrow a frequency region. This stage controls both the width the track arrived with and the width GENERATE created, so you can build broadly and then refine surgically.
7 · The guard & the FLOOR
The danger mask isn’t just a meter — it’s a guard. Widen a band too far and it glows magenta; by default a per-band mono-safe clamp caps the Side gain so correlation can’t fall below your limit. It literally cannot cancel in mono until you allow it. That’s a live correlation limiter, not a printed promise.
One control runs it: FLOOR. It sets how mono-compatible the signal must stay, globally. At its minimum the guard is off — full cancellation allowed (“I want it to cancel here”). There is no row of per-band guard switches, on purpose: mono sums the entire spectrum at once — no phone or club rig folds only above 2 kHz — so a per-band mono-safety toggle answers a question nobody asks. When the guard is actively holding a band, that band shows an amber “holding −X dB here” indicator, so the promise is always visible when it’s working.
The one legitimate per-band exception — deliberately letting a single band cancel (say, super-wide air on a headphone-first track) — is handled as a gesture on the selected band, not a permanent control. When allowed, that band turns magenta: “cancellation permitted here”.
8 · Mono-below & bass
MONO< sets a frequency below which everything folds to mono — a shaded region on the view, on by default. Bass mono is sacred here: the low end is exactly what every mono system (club subs, phones, Bluetooth) sums first, so DeltaWidth keeps it centered unless you deliberately raise or defeat the region. You widen the lows on purpose, never by accident.
9 · The Butterfly view & the delta
The Butterfly (WIDTH) view is the family signature applied to width. It draws three things at once, per band:
- Source width — a ghost of the width the signal arrived with.
- Live width — what it is now, after GENERATE and SCULPT.
- Mono-loss — the danger mask: what the mono sum would lose.
The readouts report it in dB — width in, width out, mono-loss, and guard reduction — so you see exactly how much width you added and what it costs. Hit MONO and the wings collapse: the plot paints in red precisely what is lost per band. It’s an honest A/B, not a guess.
Colour law (family-wide): magenta means danger — the mono-risk alarm, and nothing else on this plot. Source and generated width read in separate, calmer hues so at a glance you always know what’s the track’s, what’s yours, and what’s about to cancel.
10 · Resolution: ZERO & FINE
How fine the bands get is a single, honest product switch — the same trade as zero-latency versus linear-phase in DeltaEQ:
- ZERO — 8 octave bands, IIR filterbank, no latency. For tracking, live use and broad strokes.
- FINE — an FFT path, ⅓-octave or finer, at the cost of some latency. For mixing and mastering, when you need to be surgical. (Planned — not in the first build.)
FINE only affects Stage 2 (SCULPT). Stage 1 stays octave-stepped always — finer generation sounds blurry and phasey, and DeltaWidth would rather say so than offer a knob that implies finer is always better. One caveat rides FINE: at ⅓-octave in the bass the bands are narrow enough that correlation estimates get noisy, so the guard uses a longer window down there and responds more slowly. It’s stated, not hidden.
11 · Phase ↔ Capture (planned)
A planned second flavour of GENERATE folds in convolution as a single blend control, PHASE ↔ CAPTURE:
- PHASE — the Hilbert rotation above: surgical, instant, mono-bulletproof.
- CAPTURE — a modeled stereo mic-pair: a short, synthetic, flat-magnitude decorrelation applied to the Side path only, so the mono sum still equals 2·Mid exactly. More natural, believably “miked wide”, at the cost of some latency.
Both ends are width, not room — no reverb tail at either extreme. Because the IR is synthetic and flat-magnitude, mono stays pristine; because it colours the Side, the delta readout will show that colour. Like HARM, it’s powerful and easy to overdo. This flavour is designed and parked, not yet built.
12 · On the wall
DeltaWidth is a wall citizen from day one. Like every Delta plugin it reports to DeltaWall over the shared-memory registry, so its width and mono-risk appear as a tile alongside your spectra, EQ ghosts and compressors. The tile is essentially the interactive Butterfly view — and a MASK→FIX cousin can flag two tracks that are both super-wide and fighting in mono, then narrow the offender in one click.
13 · The honest caveat
Say it plainly, because it’s the whole point: there is no free width. Every decorrelation technique trades mono-compatibility for space. A clean mono collapse still means the width is gone in mono — graceful, not free. DeltaWidth’s value isn’t that it escapes this law; it’s that it draws the cost, keeps you above your own safety floor, and never lets the meter lie about what you traded.
14 · Settings & troubleshooting
Standard family settings apply: a 30/60 FPS refresh, an Eco / low-power mode (also engaged automatically under load by the performance governor), and the styling sliders that drive the view’s look. All UI and view state persists across sessions.
“It sounds wide but disappears in mono”: that’s the guard set low (or off) letting bands cancel. Raise the FLOOR until the amber “holding” indicators appear, or watch the mono-loss layer and back off the width where it’s deepest.
“The bass got weird when I widened”: check MONO< — if you’ve lowered or defeated it, the low end is being decorrelated. For most material, leave the lows mono.
“HARM sounds harsh”: it’s a Side-only saturator — a little goes a long way. Pull it back and confirm in the delta readout that you’re adding sheen, not fizz.