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14 IR CAPTURE
This section details the use of a built-in tool that allows you to capture you own Impulse Responses using the
Axe-Fx III and some additional equipment.
Whether part of a combo or housed in its own cabinet, the speaker is a major part of the sound of any guitar or
bass amp. When you hear great tone on a recording or at a live show, this means someone somewhere has done a
great job of selecting and placing mics (even if the player is already using a Fractal Audio product!).
The Axe-Fx III uses Impulse Responses (“IRs”) to faithfully reproduce the sound of a mic’d speaker, with over
2,048 Factory Cabs provided, and 2,048 more memory slots for User Cabs. Our store offers many
, but you can also create your own IRs using the IR Capture utility in the Axe-Fx III. The
process is easy and requires only some common pro-audio gear.
Learn more about Impulse Responses in the Cab Block section of
“The Fractal Audio Blocks Guide”
DECIDE ON A CAPTURE METHOD
There are two different methods of IR capture. Both methods require microphone(s) and preamp(s), and both
methods produce excellent results.
Method 1 requires a flat, neutral, full-range power amp. This will typically be a solid-state amp designed for pro-
audio applications (e.g. not a guitar-oriented amp, which would add tonal coloration).
Method 2 adds a speaker-level DI box — such as the Fractal Audio X-Load LB-2 — to “factor out” the power amp,
so you can use any amp—even a regular guitar amp.
MONITOR YOUR AXE-FX III
When creating IRs, you’ll probably want to test-drive the results right away. Connect your guitar to your Axe-Fx III
and set up whatever you’d normally use for direct, full-range monitoring (headphones, studio monitors, powered
FRFR speakers, etc.). The capture process uses OUTPUT 2 LEFT, so please ensure that Output 2 | Copy Output 1
is set to “OFF” on the Audio page of the I/O menu under SETUP.
MIC THE SPEAKER
Before you can mic a speaker, you’ll need to play through it. You can plug right in to the actual guitar amp
itself as you normally would, or you can use an Axe-Fx preset (with the Cab block bypassed or circumvented)
into a neutral power amp, into the speaker. One advantage of the latter method is that once you capture
the IR, you can use the same exact amp for testing, which should produce remarkably accurate results.
Once you’ve got a good guitar tone coming through the speaker, it is time to set up the mic(s).
Recording studios have control rooms isolated from the “live room”, making it easy to hear what
the microphone is picking up without interference from a loud amp. Having an assistant or
robot to adjust the mic is convenient. If this option isn’t available to you, try using headphones
to let you focus on the mic’d tone. It might be loud, so take care not to damage your hearing.
1
You can also record the amp and listen back to make sure you are satisfied with the tone.
1
https://www.osha.gov/SLTC/noisehearingconservation/
14 IR CAPTURE
