Mix Tools

STEREOBLOOM

A three-band stereo imager that widens, narrows and deepens without changing the mono fold-down.

£55 £69Launch price

STEREOBLOOM is not in the collection installer yet. Version 1.0.2 was built before it, and the next version will include it. Its free 10-day trial starts from inside the plug-in, as every one does, never from a download.

Formats: VST3 · AU
Operating system: macOS · Universal
Version: v1.0.0

What it does

Wider, deeper, and the same in mono.

Widening usually costs something in mono, and studio monitors hide it: a phone, a club system or a single speaker is where it shows. STEREOBLOOM does every spatial process to the side signal alone, which is the one place left plus right cannot see. With MONO LOCK on, the fold-down is the input's to floating-point precision, and the MONO SUM readout shows it live.

The side is split into three bands that always add back to exactly the input, and each band takes its own share of width, depth and spread. A correlation guard predicts what each band is about to do and holds back only the widening that would turn it anti-phase, so it catches the bad moment without narrowing everything else.

MONO SPREAD makes stereo out of a mono source with an all-pass decorrelator, so a mono vocal opens out and still folds back to itself. CENTRE LOCK keeps it off the lead vocal, kick and snare in a stereo mix, and TRANSIENT LOCK keeps it off the attacks, so drums keep their punch while their decays spread.

Key features

Mono that does not change

Every process is a change to the side signal, so with MONO LOCK on the fold-down is the input's, delayed by the reported latency. Measured below −250 dB in double precision and below −120 dBFS on the float path a host hears, under randomised settings at every sample rate and quality mode, and between −152 and −164 dB on real material through every factory preset.

Three bands that add back exactly

Only the side is split, and the split is complementary: LOW, MID and HIGH always sum to exactly the input, with no bump at any combination of band widths. The mid is never filtered, so no crossover's phase can reach the mono sum.

A guard that removes only the problem

The correlation guard predicts each band's output from the gains about to be applied and scales back only the widening that would push that band anti-phase. It falls in about 30 ms and recovers over about 800 ms, so it catches a burst without pumping, and it never narrows a source below itself.

Mono into stereo

MONO SPREAD adds an all-pass-decorrelated copy of what both channels share, with opposite signs left and right, so left plus right is still exactly the source. TIGHT halves the swirl a pitched source with vibrato gets; DIFFUSE spreads pads, ambience and whole mixes more evenly.

Attacks stay where they were

TRANSIENT LOCK closes the decorrelator's input in 0.3 ms at an onset and reopens it over 30–60 ms. At 100 % an attack's spread falls by 12.1 dB in REALTIME and 17.5 dB in HIGH, which sees it coming 1.5 ms early, while the spread in the decay stays within 1.5 dB.

Depth without a tail

DEPTH places a source further back with a short early field: sparse, diffused reflections 2.9–33 ms after the direct sound, darker the deeper. There is no feedback, so it is over by about 40 ms. With MONO LOCK on only its lateral part is added, and the fold-down still does not move.

The interface

STEREOBLOOM on its MASTER Open & Natural preset with the LOW band selected, the band's region and its controls tinted coral, low stability at 15 % and the bass anchor marked on the display. — STEREOBLOOM · 1 of 2

STEREOBLOOM spreading a mono source on its MONO Extra Wide preset: the input sits on the MONO line, the output curve rises to the WIDE line above the bass anchor, and MONO SUM still reads EXACT. — STEREOBLOOM · 2 of 2

How it works

The signal path, as the plugin’s own documentation states it.

input ──► mono → dual mono · non-finite → 0
      ──► phase repair (off / safe / strong)
      ──► M = ½(L+R)            S = ½(L−R)
            │                     ├─► split LOW · MID · HIGH (sums to S exactly)
            │                     ├─► width per band ◄── guard · bass anchor
            ├─► mono spread ─────►├─► + spread (centre lock · transient lock)
            ├─► depth field ─────►└─► + depth (side part)
            │
            └─► untouched with MONO LOCK on
      ──► L = M + S′    R = M − S′
      ──► auto gain · output · bypass (delay-compensated)

Audio

Audio demos for STEREOBLOOM are not published yet.

We would rather show you nothing than show you a demo that was not recorded through this plugin.

Measured

StereoBloomTests and StereoBloomPluginTests · Apple M4 · 48 kHz

Mono fold-down change, MONO LOCK on: below −250 dB (double) · below −120 dBFS (float)
Neutral settings: bit-exact against the latency-delayed input
Attack spread at TRANSIENT LOCK 100 %: −12.1 dB REALTIME · −17.5 dB HIGH
Peak rise, 150 % width on hard-panned full scale: +0.68 dB
Output at block sizes 1 to 2048: bit-identical
CPU, one instance, every process on: 0.64–0.81 % of one core
Test checks across both suites, licensing included: 2,714
auval: AU VALIDATION SUCCEEDED
pluginval: SUCCESS at strictness level 10

Figures are produced by this plugin’s own test suite and benchmark, on the hardware and sample rate named above. They are not estimates.

Controls

IMAGE

WIDTH: 0–200 %. Scales the stereo already there; 100 % is the input exactly, 0 % is mono. A centred source cannot move.
DEPTH: 0–100 %. A short stereo early field that places the sound further back. No tail.
MONO SPREAD: 0–100 %. Width made from what both channels share, so a mono source becomes stereo and still folds back to itself.
CENTRE LOCK: Keeps spread and depth away from coherent centre content in an otherwise stereo mix.
TRANSIENT LOCK: Keeps attacks out of spread and depth, so decays still spread.
SPREAD CHARACTER: TIGHT for vocals and anything pitched; DIFFUSE for pads, ambience and mixes.

BANDS

WIDTH · DEPTH · SPREAD: Per band, as a share of the global control: a band gets global × trim. LINK moves all three together.
LOW / MID · MID / HIGH: The crossovers, 40–1500 Hz and 800 Hz–12 kHz. Drag them on the display as well.
ANCHOR · FREQ: Below the anchor, 40–400 Hz, no width is added and nothing synthetic is created.
STABILITY: Folds the existing low side toward mono below the anchor, for a steadier low end.

PROTECTION

CORRELATION GUARD: OFF, GENTLE or STRONG: the floor each band's output correlation is held above.
PHASE REPAIR: Aligns a small, stable offset between the channels, such as a late microphone. Refuses mixes and spaced pairs.
MONO LOCK: On, nothing reaches the mid. Off, depth also adds its frontal reflections for a stronger distance cue.

OUTPUT

OUTPUT: ±12 dB.
AUTO GAIN: Matches the output's loudness to the input's, so a wider setting can be judged without being louder. For comparison, not for printing.
QUALITY: REALTIME, HIGH or MASTERING: 0, 1.7 or 21 ms of latency, fixed per mode.
MONO · SIDE · DELTA: Monitoring: the fold-down, the side alone, or only what STEREOBLOOM adds. Never saved with the session.

Technical details

Formats: VST3 · AU
Operating system: macOS 10.13 or later
Architecture: Universal: Apple Silicon and Intel
Plugin code: Sblm
Version: 1.0.0
Sample rates: 44.1–192 kHz
Latency: 0 (REALTIME), 1.7 ms (HIGH, the default) or 21 ms (MASTERING). Fixed per mode, reported exactly, and bypass is delayed to match.
CPU: 0.37–0.81 % of one Apple M4 core at 48 kHz, neutral to every process on
Factory presets: 14

Gentle Width, Open & Natural and Low-End Safe for masters; Wider for the mix bus; Expensive Width and Background Spread for vocals; Cinematic, Wide Double, Natural Space, Concert Width and Wide Overheads for instruments; Natural Stereo and Extra Wide for mono sources; Narrow Low End as a utility. Every one leaves OUTPUT at 0 dB, so its loudness change is honest.

Worth knowing

Widening makes a mix louder: it adds side energy while the centre stays where it was. AUTO GAIN matches the loudness so the comparison is fair, and is not meant to be printed.
Peaks can rise: up to +2.3 dB on the factory presets' test material. The presets leave OUTPUT at 0 dB rather than hiding that.
PHASE REPAIR and MONO LOCK off change the mono sum on purpose, and the MONO SUM readout says so whenever they do.
STEREOBLOOM is not part of S.A RACK. It is sold on its own and in the bundles.