what WIDE does
WIDE makes your stereo image wider without phase cancellation. it uses cascaded allpass filters to create frequency-dependent decorrelation between your left and right channels, following a psychoacoustic curve that matches how human hearing perceives stereo width.
unlike simple stereo wideners, WIDE works on mono sources too. it creates real perceived width from any input by generating subtle, frequency-dependent timing differences between channels. a per-band correlation constraint keeps every frequency mono-safe automatically.
controls
WIDE has 4 knobs, 2 toggle buttons, L/R solo buttons, a correlation meter, 4 draggable EQ nodes, and a mode selector.
knobs
| control | range | default | what it does |
|---|---|---|---|
WIDTH | 0-100% | 75% | how much stereo expansion. in STEREO mode: decorrelation strength. in M/S mode: side gain. in HAAS mode: delay time. |
DEPTH | 0-100% | 50% | character intensity. in STEREO mode: allpass cascade aggressiveness. in M/S mode: mid attenuation. in HAAS mode: feedback amount. |
FOCUS | 20 Hz - 5 kHz | 500 Hz | bass mono crossover. frequencies below FOCUS stay centered. everything above gets the full width treatment. draggable directly on the spectral display (syncs with the knob). default 200 Hz. |
MIX | 0-100% | 100% | wet/dry blend with auto-compensation so the wet signal never sounds louder than the dry. |
toggle buttons
| button | what it does |
|---|---|
MONO | folds output to mono so you hear exactly what mono listeners will hear. when active, also enforces a hard correlation floor to prevent phase cancellation. |
DELTA | hear only what WIDE is adding. the pure difference between processed and dry signal. useful for verifying the effect in isolation. |
L / R | solo the left or right channel. outputs one channel to both speakers so you can verify the widening effect per side. located in the mode bar next to the mode selector. mutually exclusive: activating one deactivates the other. |
correlation meter
the horizontal meter in the mode bar shows real-time stereo correlation (r) between your left and right channels. amber means safe mono compatibility. yellow means caution. red means out of phase.
a peak hold marker tracks the worst-case correlation over the last 2 seconds. if it dips into yellow or red, reduce WIDTH or raise FOCUS.
stereo modes
three modes, three different approaches to stereo expansion. the same 4 knobs adapt their behavior per mode.
STEREO (default)
cascaded allpass decorrelation. creates width from any source, including fully mono input. 40 allpass biquad filters apply frequency-dependent phase shifts following a psychoacoustic curve. the result is natural, transparent width without coloration.
- WIDTH = decorrelation amount (0% = mono, 100% = full decorrelation)
- DEPTH = allpass pole radius / cascade aggressiveness
M/S
mid/side balance. boosts the existing Side channel content and optionally attenuates the Mid channel. only works on material that already has stereo information.
- WIDTH = side gain (0 to +12 dB)
- DEPTH = mid attenuation (0-50% reduction)
HAAS
creates real perceived width from any source, including mono. applies a per-sample smoothed delay to the right channel with linear interpolation. the FOCUS knob high-passes the widening signal so bass stays centered. works on mono input.
- WIDTH = delay time (1-35 ms)
- DEPTH = widening intensity (controls injection amount)
Haas use cases by source
- drums (WIDTH 5-15%, ~2-5 ms): adds width to overheads and room mics without introducing noticeable phase issues. keep FOCUS above 300 Hz to protect the kick.
- guitars (WIDTH 8-20%, ~3-7 ms): creates a natural double-tracking effect. works especially well on rhythm guitars that need to fill the stereo field.
- background vocals (WIDTH 3-8%, ~1-3 ms): subtle spread that pushes backing vocals wider without pulling them apart from the lead. lower delay times keep things tight.
- lead synths (WIDTH 15-30%, ~5-10 ms): pronounced spatial movement for synth leads and pads. higher delay times create an obvious left/right shift.
the trade-off with Haas is comb filtering: the delayed copy creates notches in the frequency spectrum that become audible in mono. shorter delays push the first comb notch higher (less audible). use the L and R solo buttons to verify each channel sounds correct, and toggle MONO to check mono compatibility.
width shaper (EQ)
the 4 colored nodes on the spectral display let you shape where WIDE applies more or less expansion across the frequency spectrum.
how they work
- drag horizontally: move the node's center frequency (20 Hz - 20 kHz)
- drag vertically: adjust width gain (-12 to +12 dB). boost = more width at that frequency. cut = less width.
- mouse wheel on node: adjust Q (bandwidth). narrow = surgical. wide = broad.
- shift + drag: fine adjustment
- double-click: toggle node on/off
- right-click: choose channel routing and shape (bell or shelf for bands 0 and 3)
shelf mode (bands 0 and 3)
the outermost nodes (band 0 and band 3) can switch from parametric bell to shelving. right-click the node and choose "shelf" under the shape section. band 0 becomes a low shelf (affects width below its frequency). band 3 becomes a high shelf (affects width above). the Q control adjusts the shelf transition steepness.
shelf mode
hover over any node to see inline controls. click the enable dot (left of node) to toggle it on/off. for bands 0 and 3, click the type badge to cycle between BELL, LS, and HS. low shelf on band 0 shapes everything below, high shelf on band 3 shapes everything above. double-click the label text to type exact values (e.g. "2.5k +3.0 dB Q 0.7"). right-click any band for the full menu as a fallback.
node defaults
| node | default frequency | state |
|---|---|---|
| band 0 | 250 Hz | active |
| band 1 | 2500 Hz | active |
| band 2 | 800 Hz | off (double-click to enable) |
| band 3 | 6000 Hz | off (double-click to enable) |
the width shaper is powerful for source-specific tuning. for example: cut width at 200 Hz to keep bass centered, boost at 3 kHz to widen the presence range.
spectral display
the real-time spectral display shows:
- amber curve: your input signal's frequency spectrum
- width overlay: the amount of stereo expansion being applied per frequency
- colored fill: the width shaper (EQ) curve showing your node settings
- FOCUS handle: draggable handle showing the bass mono crossover point. grab it and slide to set where mono-summing begins. syncs with the FOCUS knob.
AUTO loudness matching
the AUTO toggle in the mode bar enables K-weighted loudness compensation (ITU-R BS.1770). it automatically adjusts the output level to match the input, so your A/B comparison is fair. you hear the width, not the volume difference.
display interactions
- scroll wheel: zoom frequency range (centers on cursor)
- double-click: reset zoom to full 20 Hz - 20 kHz range
- drag FOCUS handle: set the bass mono crossover frequency
presets
WIDE ships with 26 factory presets organized by stereo mode.
STEREO mode (14 presets)
| preset | use case |
|---|---|
| Subtle | gentle expansion. safe for any mix bus |
| Natural | balanced width. good starting point |
| Wide | noticeable expansion without excess |
| Ultra Wide | maximum perceived width. use on sparse mixes |
| Mono-Safe | wide but guaranteed compatible. club music safe |
| Vocal Spread | widen vocal presence region. EQ: +4 dB at 3 kHz |
| Guitar Width | widen guitars without losing center punch |
| Synth Pad | lush wide pad expansion with shimmer |
| Drum Bus | tight low end, wide cymbals |
| Mix Bus | gentle stereo polish for mastering. mono-safe |
| Air | high-frequency shimmer and openness |
| Warm Width | low-mid richness for pads and keys |
| Bass Tight | tight mono bass, wide top end. mono-safe |
| Full Spectrum | all 4 EQ bands active. sculpted width across the range |
M/S mode (6 presets)
| preset | use case |
|---|---|
| Side Boost | simple stereo widening via side gain |
| Mid Scoop | reduce center, emphasize sides |
| M/S Natural | balanced M/S expansion |
| Mastering Glue | gentle M/S for mastering. mono-safe |
| Side Hi-Fi | boost side presence and air |
| Mid Focus | keep center vocals clear, reduce side mids |
HAAS mode (6 presets)
| preset | use case |
|---|---|
| Quick Wide | short delay for subtle widening |
| Spacious | medium delay for spatial enhancement |
| Deep | long delay for pronounced widening |
| Diffuse | maximum Haas with feedback for diffusion |
| Haas Vocal | very short delay for vocal widening |
| Haas Shimmer | short delay with high-frequency emphasis |
browsing
- click the preset name or
▾chevron in the header to open the preset dropdown - use
< >arrows to browse sequentially - A/B button: compare two different settings instantly
how it works
WIDE uses a 5-stage pipeline. the core idea: create frequency-dependent phase differences between left and right channels that your brain interprets as spatial width, while guaranteeing those differences never cause mono cancellation.
input conditioning
the stereo signal is encoded into Mid (L+R) and Side (R-L) channels. the mid channel carries the center image. the side channel carries the stereo difference.
ERB spectral analysis
40 perceptually-spaced frequency bands (ERB scale) analyze the signal. each band gets an independent width coefficient shaped by a psychoacoustic curve derived from listening tests. the curve peaks at 600 Hz, where human hearing is most sensitive to stereo width.
allpass cascade
40 biquad allpass filters process the side channel. each filter is tuned to one ERB band using golden-ratio spacing (no two poles form a harmonic ratio, preventing metallic artifacts). the allpass filters change the timing of different frequencies without changing their volume, creating decorrelation that the brain perceives as width.
correlation constraint
per-band inter-channel correlation (ICC) is measured in real time. if any frequency band becomes too decorrelated (approaching anti-phase), the width for that band is automatically reduced. this guarantees mono safety by construction, not by hope.
output + auto-compensation
the processed signal is decoded back to L/R stereo. RMS-matched gain compensation ensures the wider signal never sounds louder than the original. you hear the width, not the volume.
the psychoacoustic width curve
WIDE doesn't decorrelate all frequencies equally. research by Fagerstrom et al. (DAFx 2025) showed that human hearing perceives stereo width differently across the spectrum. WIDE uses a Gaussian emphasis curve peaked at 600 Hz with a floor of 0.4 at the extremes:
- 50-100 Hz: minimal decorrelation. bass stays centered.
- 300-1100 Hz: maximum decorrelation. this is where your ears are most sensitive to spatial width.
- 1-5 kHz: declining decorrelation. presence range gets moderate width.
- 10+ kHz: back to minimal. air band gets subtle treatment.
the FOCUS knob sets the low-frequency cutoff for this curve, keeping bass mono while the curve handles the rest.
technical specifications
| spec | value |
|---|---|
| formats | VST3, AU (AUv3), standalone |
| platform | macOS (Apple Silicon native) |
| sample rates | 44.1 - 192 kHz (automatic adaptation) |
| main signal latency | 0 samples (allpass cascade is real-time) |
| reported latency | ~6 ms (from analysis FFT only) |
| CPU target | < 1.5% at 44.1 kHz, 512-sample buffer (macOS with hardware-accelerated FFT) |
| ERB bands | 40 (20 Hz - Nyquist) |
| allpass sections | 40 biquads, Direct Form II Transposed |
| pole spacing | ERB-warped golden ratio |
| stereo modes | STEREO (decorrelation), M/S (balance), HAAS (delay) |
| width shaper bands | 4 parametric bells |
| mode switching | 10 ms smooth crossfade |
| factory presets | 26 |
| metering | real-time signed correlation (r) with peak hold |
| phase modification | allpass only (magnitude preserved) |
| DRM | none. no iLok. no account. no activation. |
installation
- download the installer from kernaudio.io
- run the installer. it copies VST3 and AU to your system plugin folders
- open your DAW, scan for new plugins
- find "KERN WIDE" under manufacturer: "KERN Audio"
plugin locations
- VST3:
~/Library/Audio/Plug-Ins/VST3/KERN WIDE.vst3 - AU:
~/Library/Audio/Plug-Ins/Components/KERN WIDE.component
no activation required. no account needed. just install and use.
quick start recipes
first time? start here
- load preset: Natural
- play your audio. watch the spectral display respond
- adjust WIDTH: this is the main control. higher = wider stereo field
- watch the correlation meter in the mode bar. amber = mono safe. red = phase issues
- try FOCUS: raise it to keep more low end centered, lower it for full-range widening
- use the L and R solo buttons to hear each channel separately and verify the widening effect
- toggle A/B to compare with the original
"my vocal sounds narrow"
- load preset: Vocal Spread
- STEREO mode is ideal for mono or near-mono vocals
- adjust WIDTH to taste (start at 50-60%)
- FOCUS at 800 Hz keeps the bass centered
- toggle MONO to verify mono compatibility
"my synth pad needs more space"
- load preset: Synth Pad
- WIDTH 80%, FOCUS low at 500 Hz for lush low-mid width
- the preset boosts shimmer at 8 kHz via the width shaper
- use MIX to dial back if it's too much
"my drum bus needs wider overheads"
- load preset: Drum Bus
- FOCUS at 800 Hz keeps kick and snare centered
- width shaper boosts 8 kHz for open overhead sound
- MIX at 75% for natural blending
"i want to widen the existing stereo field"
- switch to M/S mode
- load preset: Side Boost or M/S Natural
- this amplifies existing side content without adding decorrelation
- note: M/S won't affect mono input since there's no side signal to boost
"i need a quick obvious widening effect"
- switch to HAAS mode
- load preset: Spacious or Quick Wide
- HAAS uses time delay for immediate, obvious spatial shift
- check MONO button: Haas effects can have comb filtering in mono
"mastering: gentle stereo polish"
- load preset: Mix Bus or Mastering Glue
- both are mono-safe with conservative settings
- Mix Bus uses STEREO decorrelation (MIX 60%). Mastering Glue uses M/S balance (MIX 50%)
- use A/B button to compare with bypass
tips
- watch the correlation meter. it shows mono compatibility in real time. amber = safe, yellow = caution, red = danger. no need to toggle MONO constantly.
- L/R solo verifies the effect. click L or R in the mode bar to hear each channel separately. useful for checking that widening is balanced and each side sounds correct.
- MONO is your safety net. toggle it on periodically to check mono compatibility. if something collapses, reduce WIDTH or raise FOCUS.
- STEREO mode works on everything. even fully mono input gets real perceived width via decorrelation.
- FOCUS keeps bass centered. leave it at 500 Hz for most material. raise it to keep more low-mid content centered, or lower it for lush pad-style widening.
- use the width shaper for surgical control. cut width at frequencies where bass lives. boost width at presence frequencies.
- DELTA reveals the contribution. toggle it to hear exactly what WIDE is adding. useful for dialing in subtle settings.
- M/S mode only works on stereo material. if your source is mono, use STEREO mode instead.
- HAAS creates comb filtering. it's an audible effect at extreme settings. check MONO to hear if it's acceptable for your use case.
- mode switching is click-free. 10 ms crossfade means you can switch modes during playback without pops.
- less is more on mix bus. 25-40% WIDTH with high FOCUS and 50-60% MIX is often all you need for mastering.
troubleshooting
| problem | solution |
|---|---|
| "i can't hear any difference" | increase WIDTH. make sure you're not in MONO mode. check that MIX is above 0%. on mono input, use STEREO mode (M/S won't work). |
| "the mono fold sounds thin" | reduce WIDTH or raise FOCUS. the correlation constraint prevents total cancellation, but very aggressive settings can still thin the mono fold. |
| "bass is getting blurry" | raise FOCUS to keep more low frequencies centered. use the width shaper to cut width at bass frequencies. |
| "it sounds phasey / swirly" | reduce DEPTH. high DEPTH values make the allpass cascade more aggressive. try DEPTH at 30-40%. |
| "HAAS mode has a flanging sound" | that's comb filtering from the delay. reduce WIDTH (shorter delay) or switch to STEREO mode for artifact-free widening. |
| "correlation meter shows yellow or red" | reduce WIDTH or raise FOCUS. if using HAAS mode, switch to STEREO for better mono compatibility. toggle MONO to hear the fold. |
| "CPU is too high" | WIDE targets <1.5% at 44.1 kHz on macOS (hardware-accelerated FFT). Windows CPU may be higher. at higher sample rates, CPU is proportional. |
| "plugin doesn't appear in DAW" | rescan plugins in your DAW. check that VST3/AU files exist in ~/Library/Audio/Plug-Ins/. |
keyboard / mouse reference
| action | control |
|---|---|
| adjust knob | click + drag vertically |
| fine adjust knob | shift + drag |
| reset knob to default | double-click knob |
| move EQ node frequency | drag horizontally |
| adjust EQ node gain | drag vertically |
| adjust EQ node Q | mouse wheel on node |
| fine adjust EQ node | shift + drag |
| toggle EQ node on/off | double-click node |
| zoom frequency range | scroll wheel on display |
| reset zoom | double-click on display |
| browse presets | click preset name or < > arrows |
| toggle A/B comparison | click A/B button |
| toggle MONO check | click MONO button |
| toggle delta mode | click DELTA button |
| solo left channel | click L button in mode bar |
| solo right channel | click R button in mode bar |
| switch stereo mode | click mode selector (STEREO / M/S / HAAS) |
version history
v1.3.3 (april 10, 2026)
- new: frequency-dependent spectrum smoothing — bass sits calmer, treble tracks transients more responsively (grounded in ERB critical-band integration time)
- new: peak hold ghost line — trails above the main curve when the signal stops, decays at 3 dB/sec, rendered as a solid Catmull-Rom trace in the industry-standard style (SPAN / Pro-Q)
- new: transient flash overlay — curve briefly brightens on kick, snare, or any percussive hit; baseline-subtracted so sustained music doesn't trigger it
v1.3.2 (april 7, 2026)
- refreshed visual identity: cabinet grotesk typeface, warm-tinted neutrals, redesigned arc knobs, background grain texture, spectral glow
- editable EQ values: double-click any node label to type exact frequency, gain, and Q
- improved inline controls: hover zones expanded, controls no longer disappear when moving toward them
- animated toggle button glow on MONO and DELTA buttons
- styled popup menus (preset browser, EQ routing, display options)
- smoother CPU meter display
- added stereo bus layout validation for broader DAW compatibility
v1.3.1 (april 2026)
- HAAS mode rewrite: creates real perceived width from mono sources via per-sample smoothed delay
- draggable FOCUS handle on spectral display (synced with FOCUS knob)
- FOCUS high-pass filter on decorrelation signal keeps bass centered
- DEPTH now audibly controls widening intensity across all modes
- AUTO loudness matching: K-weighted compensation (ITU-R BS.1770) for fair A/B comparison
- redesigned EQ interaction: hover for inline enable dot and type badge (BELL/LS/HS), double-click to toggle
- stereo injection capped to prevent L/R panning artifacts
- width at 0% now fully bypasses processing for clean A/B
- 104 automated tests
v1.2.1 (march 2026)
- fixed: GUI size persistence across sessions
- added: double-click outer EQ nodes for bell/shelf toggle
- added: shelf mode in Bass Tight, Full Spectrum, Mastering Glue presets
- fixed: delta, bypass, and stereo mode persist across preset changes
v1.2.0 (march 2026)
- L/R solo buttons: hear left or right channel separately to verify widening effect
- bypass button with 10 ms crossfade ramp (shared across all KERN plugins)
- resizable GUI: drag corner to scale 75%-150%, scale persists across sessions
- expanded Haas mode documentation with per-source use cases
- 99 automated tests (394,228 assertions)
v1.1.1 (march 2026)
- shelving EQ option: width shaper bands 0 and 3 can switch from parametric bell to low/high shelf via right-click menu
- spectral display +12 dB grid line and label
- 95 automated tests (392,166 assertions)
v1.1.0 (march 2026)
- mono-below-crossover: LR4 (24 dB/oct) at FOCUS frequency collapses bass to mono
- width shaping biquad filters: EQ nodes now actively shape the width signal per frequency
- real-time signed correlation meter in mode bar (r = -1 to +1, peak hold)
- HAAS feedback safety: shape filters outside feedback loop to prevent self-oscillation
- 91 automated tests (392,166 assertions)
v1.0.0 (march 2026)
- initial release
- 5-stage psychoacoustic stereo expansion pipeline
- 40 allpass biquad cascade with ERB-warped golden-ratio pole spacing
- 3 stereo modes: STEREO (decorrelation), M/S (balance), HAAS (delay)
- Fagerstrom perceptual width curve (peak at 600 Hz, Gaussian emphasis)
- per-band ICC correlation constraint for automatic mono safety
- 4-band parametric width shaper (EQ)
- RMS auto-compensation
- FOCUS bass mono crossover (20 Hz - 5 kHz)
- MONO fold check with hard correlation floor
- DELTA difference monitoring
- Direct Form II Transposed biquad implementation
- click-free 10 ms mode crossfades
- spectral transient detector (first-frame priming)
- 26 factory presets
- 79 automated tests (392,129 assertions)
design & development: Jonas Rosbech. perceptual width curve inspired by Fagerstrom et al. (DAFx 2025). ERB formula: Glasberg & Moore (1990). allpass cascade design based on published research by Schroeder (1962) and Gardner (1995).