York Audio Kw 412 M25sh Irs May 2026

The York Audio KW 412 M25-SH impulse response (IR) pack is a premium digital collection designed for guitarists using modelers like Fractal, Helix, Kemper, or DAW plugins. It is meticulously captured from fusion guitar legend Scott Henderson’s personal Kerry Wright 4x12 cabinet, which is loaded with UK-made Celestion G12M 25W Greenback speakers. Core Features and Tonal Character

This pack is celebrated for its "mix-ready" quality, offering a sound that is often described as fat and clear at the same time.

Signature Tone: Expect a warm, thick low end, a "vocal" Greenback midrange, and an articulate top end that maintains note definition without being overly harsh or "sizzly".

Resonance: The cabinet has a low resonance frequency of 115 Hz, providing a deep, organic resonance that many users find more immersive than standard Greenback packs.

The "Scott Henderson" Folder: A standout inclusion containing Scott’s personal mic placements. These are labeled from bright (57-9) to dark (57-1), allowing you to match the IR to your guitar’s tone control settings. Microphones and Mixes

The library includes a vast array of individual microphone captures and curated multi-mic blends:

Dynamic Mics: Modern and vintage Shure SM57s (57m/57v), SM58, SM7, and Sennheiser MD421 (m/v).

Ribbon Mics: Royer R-121, Beyerdynamic M160, and the Shure KSM313.

Condenser Mics: High-end options like the Telefunken U47, ADK U67, and AKG C414.

Curated Mixes: Includes over 20 multi-mic mixes, plus custom "Signature Mixes" created for artists like Jim Adkins of Jimmy Eat World. Technical Specifications

The files are delivered in standard .WAV format at multiple sample rates to ensure compatibility with all major hardware and software:

Sample Rates: 96k (Strymon, Boss), 48k (Fractal, Line 6, Neural DSP), and 44.1k (Kemper).

Resolution: 500ms for maximum detail, with natural and minimum phase versions provided.

Stereo Options: Features "Stereo Room" captures and "Stereo Mixes" (STM) designed to provide a natural "amp-in-the-room" feel, especially when using headphones. Best Use Cases

While it shines for classic rock and fusion tones, its versatility makes it a favorite for: York Audiohttps://www.yorkaudio.co KW 412 M25-SH - York Audio

Title: The Ghost in the Wire

Logline: A disgraced audio forensic analyst discovers that a vintage speaker model, the York Audio KW 412 M25SH IRS, isn't just a relic of analog sound—it’s a dormant military-grade psychoacoustic weapon, and someone just turned it on.

The Story

Rain lacquered the cobblestones of York, England’s oldest district. Inside a cluttered workshop that smelled of solder and mildew, Elias Thorne stared at the charred remains of a speaker cabinet. The blackened badge read: York Audio KW 412 M25SH IRS.

“This isn’t a speaker,” he muttered, his voice raspy from years of disuse. “It’s a confession.”

Three days ago, a former MI5 analyst named Mira Sudol had walked into Elias’s shop. She wasn’t looking for a vintage 4x12 guitar cabinet. She was looking for a ghost. For two years, she’d been haunted by a low-frequency hum—a subsonic drone that triggered panic attacks, fragmented memories, and aphasia. Doctors called it tinnitus. She called it the Shiver.

“The hum only appears near old sound systems,” she’d said, sliding a worn service manual across the counter. The cover read: York Audio KW 412 — Modified for IRS (Infra-Red Sonic) Calibration.

Elias had laughed. IRS wasn’t “infra-red.” In old York Audio engineering slang, it stood for Inverse Resonance System—a classified side project from the late ‘80s, when British defense contractors secretly repurposed guitar amps for acoustic harassment. york audio kw 412 m25sh irs

The Build

He’d spent forty-eight hours tracing the circuit. The KW 412 M25SH was a monster: four 12” Celestion M25 speakers, known for their “brown sound.” But inside this unit, the wiring was wrong. Instead of a simple series-parallel, the coils were wound with a bismuth-iron alloy—non-magnetic, reactive to neural fields. The “SH” in the model number didn’t stand for “Super Heavy.” It stood for Schumann Harmonic—a frequency that matches Earth’s own resonance, 7.83 Hz.

When played at specific amplitudes, the IRS circuit didn’t produce sound. It produced standing waves that bypassed the eardrum and resonated directly with the brain’s limbic system. You didn’t hear the York Audio KW 412. You felt it. Fear. Euphoria. Rage. Programmable emotion, delivered via quarter-inch jack.

The Crime

Elias powered up the damaged unit using a lab bench generator. The cones didn’t move. But a pressure change filled the room—a cold, sinking dread. His vision blurred. For three seconds, he saw his dead daughter’s face, then a flash of a London underground station, then nothing.

When he came to, the oscilloscope showed a spike: 7.834 Hz, modulated with a voiceprint.

“Mira wasn’t a victim,” he whispered. “She was the target.”

He pulled the service manual again. Page 47, handwritten notes: “Project Silencio. York Audio KW 412 M25SH IRS units deployed 1989-1991. Each amp paired to a single operator’s EEG signature. The amp doesn’t play music. It plays the operator’s suppressed trauma, amplified 400x, into the skull of a subject.”

Mira hadn’t been haunted. She’d been used. Someone had her old EEG profile. Someone had another York Audio KW 412 M25SH IRS—still intact, still hidden—and was broadcasting her nightmares into her brain to control her.

The Hunt

Elias traced the speaker’s serial number to a decommissioned BBC relay station outside York. He arrived at midnight, carrying only a modified Walkman and a pair of ferrofluid-damped headphones.

The station was silent except for a low, throbbing pulse—the Shiver. In the basement, a pristine York Audio KW 412 M25SH IRS sat on a shipping pallet, wired to a 1970s Revox tape machine. The tape was old, spooling endlessly. On it was a loop: Mira Sudol’s own childhood scream, recorded during a suppressed memory extraction in 1989, when she was a child subject of Project Silencio.

The amp was playing her own terror back to her, warping her present.

Elias didn’t smash the speaker. He couldn’t. Instead, he plugged his Walkman into the IRS input and played a single sound: silence. But it was a digital silence—a 24-bit null signal that forced the IRS circuit to resonate with itself.

The York Audio KW 412 M25SH IRS began to glow at the cone edges. A harmonic feedback loop built. The concrete floor cracked. Elias’s nose bled. Then, with a sound like a scream swallowed by a black hole, the speaker collapsed into its own magnetic field.

Silence.

The Aftermath

Mira woke up the next morning without the Shiver. She sent Elias a single text: “I remember everything now. Thank you.”

Elias looked at the blackened badge on his workbench. He knew there were more units out there. And somewhere, someone was still listening to the ghosts they had trapped in copper wire.

He soldered a new resistor into a broken Fender amp, hung a sign on his door—“No IRS repairs. No questions.”—and waited for the next ghost to find him.

End

Overview

The York Audio KW 412 M25SH IRS is a 4-way, bi-amped loudspeaker system that boasts an impressive combination of power, precision, and versatility. This system is designed to deliver exceptional sound quality, making it suitable for a wide range of applications, including live concerts, festivals, theatrical productions, and installations.

Design and Construction

The KW 412 M25SH IRS features a rugged, tour-grade enclosure constructed from 3/4-inch plywood, with a durable, textured finish. The speaker system is comprised of four custom-designed drivers:

• Two 15-inch woofers (M25SH) for low-frequency response
• One 10-inch mid-range driver for smooth, detailed midrange reproduction
• One high-frequency driver (1-inch exit, 1.5-inch voice coil) for crisp, accurate treble

The drivers are carefully mounted in a proprietary, computer-optimized waveguide system, which helps to control dispersion and minimize unwanted resonances.

Acoustic Performance

The York Audio KW 412 M25SH IRS is designed to deliver exceptional acoustic performance, with a frequency response of 38 Hz to 18 kHz (-3 dB). The system's bi-amped configuration, featuring two dedicated amplifiers for the low- and high-frequency sections, ensures optimal power distribution and minimizes the risk of amplifier overload.

The M25SH woofers provide deep, articulate bass, while the mid-range driver offers clear, detailed reproduction of the critical midrange frequencies. The high-frequency driver delivers crisp, accurate treble, with a smooth, even dispersion pattern.

Key Features

Some notable features of the York Audio KW 412 M25SH IRS include:

• Bi-amped design: Two dedicated amplifiers for optimized power distribution and reduced amplifier overload risk
• 4-way system: Four custom-designed drivers for comprehensive frequency coverage
• Computer-optimized waveguide: Carefully designed to control dispersion and minimize unwanted resonances
• Rugged, tour-grade enclosure: Durable construction for reliable performance in demanding environments
• Multiple rigging options: Versatile rigging system for easy installation and aiming

Technical Specifications

Here are some key technical specifications for the York Audio KW 412 M25SH IRS:

• Frequency Response: 38 Hz to 18 kHz (-3 dB)
• Maximum SPL: 126 dB (peak)
• Drivers:
  • 2 x 15-inch woofers (M25SH)
  • 1 x 10-inch mid-range driver
  • 1 x high-frequency driver (1-inch exit, 1.5-inch voice coil)
• Amplifiers: 2 x 500W (bi-amped)
• Crossover: 4-way, computer-optimized
• Enclosure: 3/4-inch plywood, textured finish
• Dimensions: 14.5 x 14.5 x 24.5 inches (HxWxD)
• Weight: 85 pounds

Conclusion

The York Audio KW 412 M25SH IRS is an exceptional loudspeaker system, designed to deliver high-quality sound and reliable performance in a wide range of applications. With its bi-amped design, 4-way configuration, and computer-optimized waveguide, this system offers an unbeatable combination of power, precision, and versatility. Whether you're a live sound engineer, installer, or audio enthusiast, the KW 412 M25SH IRS is definitely worth considering.

The York Audio KW 412 M25-SH Cab Pack is a collection of impulse responses (IRs) based on a custom-built Kerry Wright 4x12 cabinet owned by fusion guitar legend Scott Henderson. It is loaded with UK-made Celestion G12M 25-watt Greenback speakers and is designed to provide an authentic digital recreation of this specific, rare cabinet. Key Features and Content

Signature Folders: Includes a "Scott Henderson" folder containing the guitarist's personal mic placements. It also features three custom mixes created for Jim Adkins of Jimmy Eat World.

Stereo Room Captures: This pack introduced new Stereo Room captures (Small and Large Room options) and Stereo Mixes, utilizing real room ambience to create an "amp in the room" feel for headphone or stereo monitoring.

Massive Mic Selection: Over 18 different microphones were used, including classic dynamics like the Shure SM57 (modern and vintage), ribbons like the Royer R-121, and condensers like the Telefunken U47 and AKG C414.

Format & Compatibility: IRs are provided in .WAV format (24-bit 96k, 48k, and 44.1k) and are 500ms long for high resolution. They are compatible with hardware like Fractal Audio, Line 6 Helix, Strymon, and Kemper, as well as various DAW plugins. Tonal Profile Low End: Warm, thick, and resonant without being "whoopy".

Midrange: Features the classic, vocal character of Greenback speakers with a woody "thump" on pick attack.

High End: Highly detailed and articulate, offering string-to-string clarity without excessive harshness or sizzle. KW 412 M25-SH - York Audio

The Quest for the Perfect Greenback: A Look into the York Audio KW 412 M25-SH

For guitarists chasing the ultimate fusion or rock tone, the name Scott Henderson The York Audio KW 412 M25-SH impulse response

is synonymous with legendary "ear-tuned" precision. But unless you're lucky enough to own a custom Kerry Wright

4x12 cabinet, that specific magic has been hard to bottle—until now. The York Audio KW 412 M25-SH Cab Pack

is a meticulous digital recreation of Henderson’s personal cabinet, and it might just be the most detailed IR pack York Audio has ever released. What Makes This Cabinet Special?

This isn't just any 4x12. It is a custom Kerry Wright cabinet loaded with UK-made Celestion G12M 25w Greenback speakers The Signature Sound

: Unlike standard Greenbacks, this cabinet is celebrated for its "woody" midrange, thick low end, and a top end that remains articulate without becoming "fizzy" or harsh. Scott Henderson's Personal Touch

: The pack includes a dedicated "SH" folder featuring Henderson’s own microphone placements, which he meticulously compared against his physical cabinet. Next-Level Fidelity

: To capture this specific unit, Justin York upgraded his studio with mastering-grade conversion and new preamps to ensure the digital version was indistinguishable from the real thing. Key Features of the Pack 18 Microphones : A massive selection including classics like the (modern and vintage), Royer R-121 Beyerdynamic M160 , and high-end condensers like the Telefunken U47 Stereo Room Captures

: One of the most exciting additions is the inclusion of real stereo room ambience (captured with an AEA R88). This provides an "amp in the room" feel that is particularly effective for headphone users. Artist Signature Mixes

: In addition to standard mixes, the pack features three custom mixes created for Jim Adkins of Jimmy Eat World , who now uses these IRs for his live touring rig. Tonal Performance and Versatility

While it excels at the "edge of breakup" fusion tones Henderson is known for, users have found it surprisingly versatile: Classic Rock

: Pairs perfectly with JCM 800 or Plexi models for that iconic British snarl. Modern Gain

: Offers more note clarity and string definition than typical Greenback packs, making it "meaty and punchy" enough for modern styles. Bass Performance

: Some users have even reported "stunning" success using these IRs for bass, noting the full low-mids sit perfectly in a mix. Quick Tech Specs : .WAV (24-bit 96k, 48k, and 44.1k). Resolution : 500ms for maximum detail. Compatibility

: Tested with Fractal Audio, Line 6 Helix, Kemper, Strymon Iridium, and all major DAW plugins. Impedance Curve

: For Fractal users, a "4x12 Basketweave" curve with a low frequency set to is recommended for the most accurate response.

Whether you're a Scott Henderson devotee or just a "Greenback hunter" looking for a cab that sounds fat yet clear, the KW 412 M25-SH is a high-water mark for impulse response technology. Are you planning to use these IRs for studio recording live modeling rig KW 412 M25-SH - York Audio

I searched for “york audio kw 412 m25sh irs” , but this specific string does not appear to match any known commercial product, vintage audio component, or industry designation.

It seems likely this is a typo or a string of numbers/letters from multiple sources (e.g., a York Audio speaker cabinet model, an M25SH driver code, and “IRS” possibly referring to Infinity’s IRS reference speakers or a parts inventory system).

Below is a helpful essay-style breakdown of how to interpret and resolve this, plus guidance on finding what you actually need.

Subwoofer integration

• Use low-pass on sub (around 80–100 Hz) and high-pass on KW-412 at same frequency.
• Adjust crossover slope and phase to minimize cancellation (invert phase on sub if needed during alignment).
• Use measurement mic and RTA or real-time analyzer for best results.

Best uses

• Desktop PC audio and gaming
• Small-bedroom music listening
• TV sound enhancement in small rooms
• Entry-level hi-fi setups paired with an inexpensive amp or DAC

The "Classic" Mixes (SM57 + R121)

• Tone: This is the sound of Appetite for Destruction and Back in Black. The Royer ribbon tames the harshness of the SM57, giving you a smooth top-end that rolls off like analog tape.
• Best for: Plexi models, Fuzz pedals, and single-coil Strats. It takes the "ice pick" out of a Telecaster bridge pickup.

Key Findings

1. Cabinet & Speaker Authenticity

• Cabinet: Late 70s Marshall basketweave (non-metal grille). This cab type is less beamy and more diffused than modern straight cabs.
• Speakers: The M25SH refers to Celestion G12M-25 "Heritage" or vintage spec (25 watts, 75Hz cone). These have a looser low end, a pronounced upper-mid growl (1.5–3kHz), and a smoother 4-5kHz presence peak compared to modern Vintage 30s or T-75s.

2. Microphone Mixes (Key Assets)

• SM57 (Cone edge/Cap edge): The "classic rock" sound. Focused, punchy, with the signature greenback mid-hump. No ice-pick harshness.
• Royer R-121 (Ribbon): Darker, fuller, and thicker. Excellent for layering under the 57 to add weight and smooth sibilance.
• YA "Mixed" presets: York Audio’s proprietary blends (e.g., "M25-SM57-R121") are the standout feature. They deliver a pre-EQ’d, mix-ready tone that requires minimal post-processing.

3. Performance in Context

• Cleans & Edge-of-Breakup: Excellent. The M25s compress naturally; chords sound woody and chimey, not sterile.
• Crunch & Classic Rock (Plexi, JCM800): The ideal use case. The IR retains the amp’s dynamics while adding a thick, "knock" on palm mutes.
• High Gain (5150, Rectifier, Revv): Surprisingly good. The M25’s lack of extreme low-end boom prevents flubbiness. The upper-mid growl cuts through a dense mix without fizz. Note: Not for modern "scooped metal" (use York’s V30 packs for that).

4. Technical Specs (Solid Data)

• Sample Rate: 44.1kHz, 48kHz, 88.2kHz, 96kHz (WAV).
• Bit Depth: 24-bit.
• Length: 500ms (standard), 200ms (low latency options included).
• Minimum Phase: Yes, time-aligned for zero phase cancellation when blending.
• File Count: ~150+ IRs per pack (organized by mic, position, and mix).

2.2 The Celestion G12M-25 (Greenback)

The "M25SH" designation refers to the specific driver load: the Celestion G12M-25, colloquially known as the "Greenback."

• Character: These speakers are famed for a frequency dip in the upper-mids (around 4kHz) and a prominent boost in the lower-mids (100Hz–200Hz).
• Tonality: They provide a "creamy," gritty texture with a warm low-end.
• Relevance: When paired with the tight construction of a Kerry Wright cab, the result is a hybrid tone: the Greenback midrange warmth is preserved, but the often "flubby" low-end associated with vintage Greenbacks is tightened by the cabinet construction.

Typical specs (reasonable defaults)

• Frequency response: ~60 Hz–20 kHz (with subwoofer: down to 40 Hz)
• Impedance: 4–8 ohms (passive) or internal amp for powered speakers
• Sensitivity: ~85–90 dB SPL
• Dimensions: compact desktop-friendly footprint

Key features to expect

• Compact bookshelf/satellite form factor
• 3–5" woofer drivers with silk or coated paper cones
• Tweeter: 0.75–1" dome for detailed highs
• Power: 20–60W RMS per channel (powered models) or passive variants for use with an amp
• Inputs: 3.5mm aux, RCA, possibly optical or Bluetooth on newer versions
• Bass augmentation: small active subwoofer or passive radiator (M25SH IRS)
• Simple tone/volume controls; wall/desk placement options