Darwin's Cat
Free Guitar Cabinet IR Utility

Free Guitar Cabinet IR Utility

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Prepare a guitar cabinet impulse response right in your browser — no upload to a server, no signup, no paid limits. Inspect, trim, normalize, convert to mono, apply HPF / LPF, change sample rate, export WAV ready for any IR loader.

This is an online Cabinet IR Editor: an editor and converter for guitar impulse responses for Quad Cortex, Line 6 Helix, Strymon Iridium, BOSS IR-200, Walrus ACS1, Hotone Ampero II, ENGL Cabloader and software IR loaders.

The main upside — you don’t just see the IR’s parameters, you hear the result immediately through a DI guitar: dry DI, through the original IR and through the processed IR, each with its own fader.

All processing runs in the browser — your files never leave it.

Quick start

  1. Drop a WAV IR file into the upload zone.

  2. Pick a target device (Quad Cortex / Helix / Iridium / IR-200 / ACS1 / Ampero II / Cabloader) or stay in manual mode.

  3. Turn on silence trim and pick an IR length if you want.

  4. Listen through a DI guitar (your file or one of the built-in samples).

  5. Download the ready WAV — the filename is generated automatically from your settings.

What is a cabinet IR and why you need one

A guitar cabinet impulse response (IR) is a short audio recording (typically 20–500 ms) that captures how the chain of speaker, cabinet, microphone, mic position, room and recording chain reacts to a single impulse. Then any software or hardware IR loader runs a convolution of your dry signal with that IR — and a bare preamp or processor sounds like the guitar is going through a real 4×12 V30 miked with a Shure SM57 two centimetres from the dust cap.

In practice: an IR is a snapshot of a cabinet and a microphone. A good IR pack gives the same flexibility as a real amp through a mixing desk in a studio — dozens of speakers, different microphones, different positions — without renting a room, treating acoustics or making noise.

Modern modelers (Quad Cortex, Helix, Tone Master Pro, Iridium, etc.) already have an IR block in the signal chain. But IRs from third-party libraries rarely fit a project perfectly:

  • one has too much low end, booms and clashes with the bass guitar;

  • another fizzes on top under distortion;

  • a third one is stereo, your hardware wants mono;

  • the fourth is at 96 kHz, the preset wants 48;

  • the fifth is 5 seconds long because it captures the room reverb and eats a slot in your hardware.

This utility solves all of that in a few clicks.

Got a favourite pedal but no cabinet? That’s normal

Typical home situation: your favourite distortion pedal, overdrive or preamp pedal — Tube Screamer, V4 The Sheriff, Friedman BE-OD, JHS Andy Timmons, whatever. You plug straight into the interface, into the DAW — and it sounds harsh, sharp, like a saw. Especially on distortion: the guitar turns into a mosquito whine with a hissing tail, unusable.

Why: without a cabinet you’re hearing a bare pickup processed by the preamp. After the preamp it’s the speaker, the cabinet and the microphone that radically change the character of the signal: the speaker physically rolls off everything above 5–6 kHz (where the «saw» comes from), tames the rumble below 80–100 Hz, and adds the cabinet/mic resonances. Without that the signal usually sits poorly in the mix — even with the best EQ.

Recording a real cabinet at home is a separate task:

  • a live 4×12 plus a microphone doesn’t fit the room;

  • neighbours don’t share the enthusiasm at 11 pm;

  • tracking a cabinet is its own art: mic position, phase, room, acoustics;

  • simple «cabinet sim» plugins don’t always deliver the mic-and-cabinet character a specific mix needs.

An impulse response solves it in a single line: drop an IR loader (software or hardware) after your pedal — and you get the sound of a real, studio-miked cabinet. The harshness goes away, body and character appear. The same IR delivers a stable cabinet layer in headphones, on monitors and in the mix.

Where to download ready IRs

If you don’t have IR packs yet — here are tested sources to start from. Everything below is legally available for free, but check each pack’s licence before commercial use.

Source What’s inside Why grab it

Origin Effects IR Cab Library

Brown Deluxe, Magnatone 213, Fender Twin JBL, Vox AC30, Fender 5E3 Tweed Deluxe

The best free start for combo / open-back character

Shift Line Guitar HD IR Pack 1 Free

Fender Deluxe Reverb, Vox AC30, Fender Bassman 4×10

A baseline Fender / Vox / Bassman sound

Celestion Free IR

Demo samples of official Celestion IRs

To hear the «real» Celestion approach

Line 6 Allure Pack

A general-purpose guitar pack

A starting point for Helix / QC / TMP

Redwirez Free Marshall 1960A Greenback

Marshall 1960A Greenback

Closed-back 4×12 for rock — a contrast against open-back

TONE3000 and ToneHunt

Community IRs + NAM

Rare variants from enthusiasts; quality varies

For most jobs the first two packs are enough. Download, run them through this utility with the preset of your device — and you’ll get a file ready for Quad Cortex, Helix, IR-200 or whatever you’ve got.

If you want to step into paid territory — York Audio (especially DXVB Verb Deluxe for Fender clean and VX30 212 Blue for Vox), OwnHammer Imperial Bundle (a universal set), and Celestion Plus (official Celestion with various microphones).

What the editor does

Note
 The editor prepares an existing WAV-IR — cleans, converts, filters and exports it. It is not an amp modeler or a cabinet generator: the IR itself must come from a commercial pack, a free source or your own recording.

  1. Inspect. Shows sample rate, bit depth, duration, channel count, peak in dBFS, RMS, leading silence, max-peak position. You see right away what kind of IR you got.

  2. Trim leading silence — moves the impulse to the start of the file so there’s no perceived delay.

  3. Truncate length — keeps only the useful start. Shorter IR = less CPU, tighter sound, but you may lose tail resonance.

  4. Mono conversion — for hardware IR loaders that want mono (most of them).

  5. HPF / LPF — gentle tone shaping: remove rumble below 80 Hz or saw above 8 kHz.

  6. Normalize — pushes the peak to the chosen ceiling (e.g. −1 dBFS) so all your IRs sit at the same level.

  7. Sample rate and bit depth conversion — resample to 44.1 / 48 / 88.2 / 96 / 192 kHz, export as 16-bit PCM, 24-bit PCM or 32-bit float.

  8. Device presets — pick Quad Cortex or Iridium, the utility sets the right format automatically.

  9. Preview through a DI guitar. Load your own DI or pick a built-in Darwin’s Cat sample — and listen to the original IR, the processed IR and the dry DI side by side, each with its own fader.

Step by step

  1. Drop a WAV in the top zone. The file is decoded; technical data and a waveform appear.

  2. Pick a target device in the «Target device / format» block — or leave it on «Custom» and tweak the params yourself.

  3. Prepare the IR in the «Prepare IR» block: enable trim, pick a length, normalize the peak, add HPF/LPF if needed.

  4. Listen in the «Preview» block: hit «Through processed IR» — that’s the key channel where you hear the final result.

  5. Download in the «Export» block. The filename is generated from your settings automatically.

Between steps 3 and 4 you can tweak forever — the preview updates itself.

What affects what: parameter matrix

Parameter What it changes Audible in preview? Affects the downloaded file?

Channels (mono / mix / left / right)

Channel count and content

Yes

Yes

Trim silence

Removes silence before the impulse

Yes

Yes

IR length

Truncates the tail to 20/50/100/200/500 ms

Yes

Yes

Normalize

Pushes the peak to the target dBFS

Yes

Yes

HPF / LPF

Cuts low or high end

Yes

Yes

Target sample rate

Resamples the IR

Yes

Yes

Target bit depth

Quantization to 16/24/32 bit

No (preview is always float)

Yes

Device preset

Sets all of the above in one go

Yes

Yes

The most common confusion is bit depth. The browser always works in 32-bit float during preview, so 16-bit and 24-bit sound identical here. The difference only shows up in the downloaded file. Pick 24-bit as the safe default; 16-bit only if your hardware explicitly demands it; 32-bit float if you want maximum headroom for DAW work afterwards.

Parameters one by one

Trim leading silence

An IR can have anything from a fraction of a millisecond to tens of milliseconds of silence before the impulse — recording artifacts. If you keep it, the guitar signal arrives with micro-latency and the cabinet feels «sluggish» and «late».

Trim looks for the first sample above a −60 dB relative threshold from the peak, keeps a small 0.2 ms pre-roll (so the attack isn’t cut off), and shifts everything to the start.

Always turn it on, except when you’re deliberately working with a reverb-tail pre-delay (irrelevant for a cab IR).

IR length (truncate)

Different hardware IR loaders fit different amounts of data:

Device / format Typical IR length

Quad Cortex

1024 samples (~21 ms at 48 kHz)

Helix / HX

2048 samples (~42.7 ms at 48 kHz)

BOSS IR-200

up to 500 ms

Strymon Iridium

up to 500 ms

Walrus ACS1

200 ms

Hotone Ampero II

2048 samples (~46 ms at 44.1 kHz)

ENGL Cabloader

1024 samples (~23 ms at 44.1 kHz)

BOSS IR-2

200 or 500 ms
Note
 Exact limits depend on the firmware version and the official IR manager of your device. Before bulk-converting, double-check your loader’s docs.

What different lengths sound like:

  • 20 ms — very tight, no tail; «mic in the combo» feel, good for metal and aggressive rhythm work.

  • 50–100 ms — the sweet spot for most styles; cabinet body without smearing.

  • 200 ms — adds a room tail, good for blues, ambient, cleans.

  • 500 ms — almost a room sound with natural reverb.

A 2 ms fade-out is applied at the cut to avoid a click on the hard edge.

Normalize

IRs from different packs are recorded at different levels. If you switch between them, cabinets jump in volume. Normalize aligns them all to the same peak (−0.1 / −1 / −3 dBFS).

The default −1 dBFS is a safe compromise: the signal after the cabinet doesn’t clip, but doesn’t lose loudness either.

HPF / LPF

Not «technical cleanup» but tone shaping. Use deliberately:

  • HPF 60–100 Hz — removes rumble, stage noise and stand vibrations. Especially useful when the IR competes with the bass in the mix.

  • LPF 6–12 kHz — tames mic fizz under distortion. A real guitar speaker rolls off above 5–6 kHz anyway, so an LPF often makes things sound more realistic, not less.

With filters off the sound doesn’t change. If you turn them on — normalization is recommended, because a filter can lower the peak and the IR ends up quieter overall.

Channels (mono / stereo)

A real cabinet captured by a single mic is mono. Most guitar IR packs are mono. Most hardware IR loaders expect mono.

If the file is stereo, that may be a microphone pair, room/ambient channels, a finished stereo mix or an artificially widened variant. Options:

  • Mix L+R/2 — the most honest path for a two-mic capture.

  • Left only / Right only — when L and R are different, you pick.

  • Keep original — for devices that support stereo IRs (Iridium, IR-200, Captor X+).

Target sample rate and bit depth

Sample rate. Most hardware expects 44.1 or 48 kHz. If your IR is at 96 or 192 kHz, your loader will either resample it on its own (with unpredictable quality) or refuse to load. Better to resample upfront in the utility.

The browser’s OfflineAudioContext resampling generally provides quality that’s good enough for IR prep, but the exact implementation depends on the browser.

Bit depth. 24-bit PCM is the standard for all IR loaders. 16-bit only if the hardware explicitly requires it (some older units). 32-bit float for further DAW work.

Device presets

If you have a hardware IR loader you don’t need to set parameters by hand — pick it in the «Target device» dropdown and the utility will set:

  • sample rate;

  • bit depth;

  • the right mono / stereo mode;

  • IR length in samples or milliseconds.

Below that a hint appears with a source — a link to the official device docs so you can verify the values are still current.

Devices supported in the current version: Neural DSP Quad Cortex, Strymon Iridium, Line 6 Helix / HX, BOSS IR-200, Walrus Audio ACS1, Hotone Ampero II, ENGL Cabloader. For anything else, use manual mode.

Preview through a DI guitar

Numbers on screen are an abstraction. The real check is hearing how the IR sits on your guitar. So the utility has three playback channels:

  1. Dry DI — guitar without a cabinet. Your reference point.

  2. Through original IR — what’s in the file unprocessed.

  3. Through processed IR — the final result with your settings.

Each channel has its own fader, because convolution with an IR makes the signal noticeably louder than the dry DI — that’s normal, not a bug (see the math of convolution).

If you don’t have a DI handy — pick one of the built-in samples below the drop zone. They’re real dry guitar takes from Cat’s Hard Day, Deep Space is My Home, Fifth Dimension and Eleven Light Years. Each is recorded through a different preamp / pedal (Tube Screamer + V4 The Sheriff, V4 The Kraken, V4 The Copper) — handy for hearing how the same IR sits on different gain stages.

The sample loops, so you can tweak settings and hear the result instantly. When you change anything in «Prepare IR», the processed channel re-renders automatically.

Export

The filename is generated from your settings automatically, for example:

v30-greenback_helix_2048sa_mono_48k_24bit_norm-1.wav

You can read off: source v30-greenback, preset helix, length 2048 samples, mono, 48 kHz, 24-bit PCM, normalized to −1 dBFS. You can edit the name by hand before downloading.

The file is saved to your computer through a normal browser download — nothing goes anywhere.

Why is it free

Darwin’s Cat is an art project, and this utility is part of our exchange with the scene: you can prepare an IR in 30 seconds without paying for software or plugins. No signups, no telemetry, no ads. Just a tool that works.

If you want to support — listen to our music or share the page with a guitarist who’ll find it useful.

Frequently Asked Questions

What is a guitar cabinet IR and why do I need one?
An impulse response (IR) is a short recording (usually 20–500 ms) that captures how a speaker, cabinet, microphone, mic position, room, and recording chain react to a single impulse. An IR loader convolves your dry signal with this IR — and a bare preamp suddenly sounds like it went through a real cabinet miked in a studio. Without a cabinet, a direct preamp signal sounds harsh and saw-like; an IR fixes that.
Does this work with Quad Cortex, Helix, IR-200, Iridium?
Yes. The utility exports standard WAV that any hardware or software IR loader can read. Pick your device preset (Quad Cortex, Helix, Iridium, IR-200, ACS1, Ampero II, Cabloader) and the format adjusts automatically: sample rate, bit depth, mono/stereo, length in samples or milliseconds. Exact limits depend on firmware and the official IR manager — double-check your device's docs.
Are files uploaded to a server?
No. All processing runs in the browser via Web Audio API. Open DevTools → Network — after the page loads, no files are sent anywhere. Only the built-in demo samples from Darwin's Cat are fetched from the server, but that's static content; your own audio never leaves the browser.
1024 vs 2048 samples — which truncation should I pick?
Depends on the device. Quad Cortex and ENGL Cabloader are limited to 1024 samples — there's no choice. Helix-family at 2048 gives a bit more 'body', at slightly more CPU. For metal and tight rhythms 1024 is enough; for blues, clean tones, jazz — 2048 sounds better. On Iridium / IR-200 / ACS1, length is in milliseconds — 100–200 ms is a universal default.
Why is the IR-processed signal noticeably louder than the dry DI?
Expected, not a bug. ConvolverNode with normalize=true divides output by the IR's RMS, but an IR is a short impulse with low RMS, while a guitar DI is a long note with relatively high RMS. The convolved output ends up 6–12 dB louder than the dry. Every hardware and software IR loader has an output trim for this reason. In this utility each preview row has its own gain — set Dry, Original IR and Processed IR to comfortable levels.
How do 16/24/32-bit settings sound different?
In preview — they don't. The browser always renders in 32-bit float, so 16-bit and 24-bit sound identical here. The difference only shows up in the downloaded file. 24-bit PCM is the safe default for most IR loaders. 16-bit only if hardware explicitly requires it. 32-bit float if you want maximum headroom for further DAW processing.
Do I need separate IRs for clean and high-gain?
Mathematically a single IR works the same with any input — that's its linear nature. In practice, for high-gain people often pick denser, darker IRs (or apply LPF), and for clean tones — more open IRs with more room/air. Many IR packs already include separate mic-mix variants for clean and high-gain — that's a different IR pick, not a different cabinet.
Will this remove fizz from my tone?
Only partly. LPF at 6–8 kHz tames the top end and the signal becomes less 'saw-like'. But real fizz usually comes from an overdriven preamp, not from the IR. Cures: lower the preamp gain, soft-limit before the IR, or put a Tube Screamer / overdrive in front to tighten the low end and shape the attack.
Can I undo the processing on an IR?
No. Trim, mono conversion, filters, resampling are destructive operations. Keep originals separately and work on copies. To compare 'before' and 'after' in the browser, hit Play on 'Through original IR' and compare with 'Through processed IR'.
Why HPF and LPF if I already have a finished IR?
Tone shaping, not technical cleanup. HPF 60–100 Hz removes rumble, stage noise and stand vibration — especially useful when the IR competes with a bass guitar in the mix. LPF 6–12 kHz tames mic fizz on distortion. A real guitar speaker rolls off above 5–6 kHz anyway, so LPF often makes the signal feel more realistic, not less. Both filters are off by default.
What does this utility NOT do?
It's not an amp modeler or cabinet generator. It does not model nonlinear speaker behavior at high SPL, power amp saturation, or room reverb as a separate effect. It prepares an existing WAV-IR: cleans, converts, filters, normalizes and exports it in the right format. The IR itself has to come from somewhere else — a commercial pack, free sources from the section above, or your own recording.
What samples are used in the preview?
Dry guitar tracks from real Darwin's Cat songs: 'Cat's Hard Day' (Tube Screamer + V4 The Sheriff), 'Deep Space is My Home' (V4 The Kraken), 'Fifth Dimension' (V4 The Kraken) and 'Eleven Light Years' (V4 The Copper). Each is recorded through a different preamp / pedal — useful for hearing how the same IR sits on different gain stages.
Does this work offline?
Yes. After the first page load, all processing runs locally in the browser via Web Audio API. You can disable Wi-Fi and keep working. Only the built-in demo samples are fetched on first click — your own files never go anywhere.
Does it work on mobile?
It generally does — Chrome / Safari on iOS and Android support Web Audio API and AudioWorklet. But the interface is built for desktop first: sliders and tables are less convenient on a phone. For real IR work, open the page on a laptop.