What is an impulse response in guitar terms?
An impulse response (or IR) is a sonic measurement of the sound of a speaker, room or microphone in relation to a sound source. In guitar terms, this is usually your amp.
After your guitar itself and the dialled-in tone of your amp, there’s a lot more that can affect your sound. The speaker type, the space you’re in, the microphone you’re using, the microphone’s preamp or position – the list goes on.
The idea of an impulse response is to capture all of that information in one go, so you can instantly recall that setting. This means that wherever you are, you can retain your preferred tone, right down to the detail of your favourite mic placement and room sound. On stage, in the studio, jamming with friends – sorted.
Impulse responses – the scientific bit
It’s worth mentioning at this point that the term ‘impulse response’ is not exclusively used to refer to guitar amps and music production. The scientific explanation is, broadly-speaking, the measurement of an output reacting to a brief input signal (the impulse).
This could be an electronic current, an economic calculation, or a sound – that’s what we’re working with.
How do you use an impulse response?
Impulse responses are usually saved as generic .wav files. Many companies, producers and artists release their own impulse responses that allow you to accurately replicate their sounds. Alternatively, you can create your own – more on this later.
Once you’ve got your chosen IR file, you can load it into compatible hardware or software to reproduce your desired tone. Because impulse responses are becoming more and more commonly used, many manufacturers offer easy built-in ways to utilise them.
Many modern Cab Sim Pedals such as the TC Electronic Impulse and Two Notes Torpedo C.A.B. M+ feature IR loading, making using IRs easier than ever. You can simply carry all of your favourite presets on your pedalboard.