Best Impulse Responses for Guitar — IR Guide for Home Recording
Impulse responses are the hidden component that makes modern direct guitar recording possible. Without them, amp simulation plugins produce a convincing amp preamp sound but lack the final, crucial element: the speaker cabinet and microphone combination that converts the amplified signal into recorded guitar tone. With quality impulse responses, the complete signal chain — amp preamp, power stage, cabinet, microphone, room — is represented in the recording, and the result is frequently indistinguishable from a miked real amp.
Understanding what impulse responses are, where to get the best ones, and how to use them effectively is essential knowledge for any serious home recording guitarist.
What Is an Impulse Response?
An impulse response (IR) is a short audio file that encodes the complete frequency response and decay characteristics of a physical system. For guitar cabinet purposes: a test signal (a sine sweep or impulse) is played through a real speaker cabinet, captured by a microphone in a specific position, and the resulting recording is processed mathematically into a WAV file.
When this WAV file is loaded into a convolution reverb or dedicated IR loader, any signal passing through it is processed by the cabinet's captured frequency characteristics. If the IR was captured from a 1965 Marshall 1960A cabinet loaded with Celestion Greenbacks, a microphone 1 inch off-centre at the speaker cone edge — the IR applies those exact frequency characteristics to your amp sim signal. The output sounds as though it was recorded through that specific cabinet in that specific microphone position.
The practical implication: you can access the exact frequency characteristics of rare vintage cabinets (1960s Vox AC30, 1970s Marshall 1960A, vintage Fender piggyback cabs) from your home studio, without owning, storing or miking the real equipment.
Key IR Specifications
Format: Standard guitar IRs are WAV files — typically 44.1kHz or 48kHz, 24-bit, mono. Stereo IRs exist for stereo guitar rigs but are less common. Most hardware and software accepts standard 44.1kHz 24-bit mono WAV.
Length: Guitar cabinet IRs are typically 200–500ms long. Longer IRs capture more room reflections; shorter IRs are more focused and dry. Most IR loaders truncate longer IRs to their practical useful length.
Phase: Minimum-phase IRs (most common) and linear-phase IRs process differently and have different latency implications. For real-time playing through amp sim chains, minimum-phase IRs are preferable for lower latency.
Celestion IR Store — Official Speaker Manufacturer (£3–6 per IR)
Celestion manufactures the most iconic guitar speakers in history — the Vintage 30, G12M Greenback, G12H, Blue, Gold. Their IR store offers official captures of every current speaker model, recorded in specific cabinets with multiple microphone options.
Buying from Celestion means buying the definitive version of each speaker's sound — captured by the manufacturer who knows the product most intimately. Each IR pack includes multiple microphone positions (SM57 on-axis, SM57 off-axis, Sennheiser MD421, Royer R-121 ribbon, condenser overheads) allowing the user to blend microphone characters as a recording engineer would in a real studio.
Essential starting IR: Celestion G12M Greenback (£3 per IR). The Greenback is the foundational British cabinet speaker — used in original Marshall 4x12s, countless classic rock recordings, and still in production. It has a warm, complex low-mid character and a slightly rolled-off high end that suits rock and blues applications perfectly. The SM57 on-axis Greenback IR is a universally applicable reference point for any rock or blues recording.
Celestion Vintage 30: The most commercially successful Celestion speaker — used in Mesa Boogie, Marshall and countless other cabinets. Bright, scooped, with a pronounced presence peak at 3–5kHz. The standard modern rock and high-gain cabinet sound. Available individually (£3) or as a full pack with multiple microphone positions.
Ownhammer — Professional Multi-Mic Captures (£30–50 per pack)
Ownhammer has produced some of the most respected IR libraries available, with a focus on vintage cabinet accuracy and multiple microphone position variety. Their packs typically include dozens of IRs from a single cabinet — every combination of primary close microphone (SM57, MD421, Royer R-121) with room microphone options and blend positions.
This variety is specifically useful for players who want to use IR mixing (blending two or more IRs from the same cabinet at different positions) to create a more complex, three-dimensional cabinet character — approximating how professional engineers blend multiple microphones when tracking a real amp.
Ownhammer's vintage Marshall 4x12 packs (capturing late-1960s and early-1970s original cabinets) are particularly well-regarded — these cabinets are rare and expensive to own; their precise frequency characteristics are available in Ownhammer packs for £30–50.
Best for: Professional home recording, players who want extensive microphone position variety, those doing serious studio work.
York Audio — Best Modern Alternative (£25–40 per pack)
York Audio's IR library has grown significantly in reputation over recent years — particularly for high-gain and modern applications. Their captures have a slightly different voicing character from Ownhammer — some players prefer one; others prefer the other. Both are excellent at the professional level.
York Audio's free IR samples (small packs available as introductory downloads from their website) allow players to evaluate their house sound before purchasing full packs. Their free samples are genuinely usable in professional contexts — not crippled demonstrations.
Best for: High-gain and modern applications, those who want to try before buying.
Two Notes — Hardware-Integrated IR System
Two Notes manufactures hardware load boxes (Torpedo Studio, Torpedo Live) and guitar processors (Captor X, Reload) that include built-in IR loading capability. Their Wall of Sound software platform and associated IR library are optimised for Two Notes hardware but also function as standalone DAW plugins.
For players using Two Notes hardware for direct recording, their Celestion-licensed IR library (built into the Two Notes ecosystem) provides official captures within a convenient, integrated workflow.
Using IRs in DAW Amp Sim Chains
Loading impulse responses in a DAW-based amp sim chain involves an IR loader plugin between the amp sim and the output:
Amp sim plugin (Neural DSP Archetype, Bias Amp 2, Amplitube) — handles preamp and power amp simulation. Most amp sim plugins have a built-in IR loader as part of the signal chain.
Standalone IR loader (LiquidSonics Convology XT, Pulse by Ignite Amps — free, Two Notes Wall of Sound) — for use with amp sims that separate the cabinet stage.
Load the IR WAV file into the IR loader slot. The loader processes the signal in real time with zero additional noticeable latency (minimum-phase IRs).
Mix multiple IRs (most advanced loaders support blending two IRs) for more complex cabinet character.
FAQ
Q: What is a guitar impulse response? A: A short audio file that captures the frequency response of a specific speaker cabinet and microphone combination. Recorded by playing a test signal through the real system and mathematically processing the result. Loaded into a convolution reverb or dedicated IR loader, it applies the exact frequency characteristics of that cabinet and microphone to any guitar signal passing through it — making a direct recording sound as though it was miked through that specific cabinet.
Q: Do I need paid IRs, or are free ones good enough? A: Free IRs — from Celestion's introductory samples, Ownhammer and York Audio free packs, and various forum sources — are adequate for home recording and demos. Paid IR packs from Ownhammer and York Audio offer more precisely captured vintage cabinets with greater microphone variety, and are worth the investment for professional recording work where the exact character of specific vintage equipment matters. For most home recording applications, free IRs are a legitimate starting point.
Q: What format are impulse responses? A: WAV files — typically 44.1kHz or 48kHz sample rate, 24-bit depth, mono. This is the standard format accepted by virtually all hardware units (Axe-FX III, Fractal FM9, Line 6 Helix, Two Notes Torpedo series) and DAW IR loader plugins (LiquidSonics Convology XT, Neural DSP integrated loaders, Pulse by Ignite Amps). Ensure the sample rate matches your DAW's project sample rate to avoid conversion artefacts.
Q: What is the best Celestion IR to start with? A: The Celestion G12M Greenback (£3 per individual IR) is the recommended starting point — the Greenback is the most historically significant British guitar speaker, used in original Marshall 4x12 cabinets on countless classic rock and blues recordings. Its warm, complex character is broadly applicable across rock, blues and country. The SM57 on-axis position from the Greenback pack is the correct initial choice — it approximates how most classic guitar recordings were made.