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I'm trying to grasp a concept of an impulse responses and getting a little bit confused. Most commercially available ones are meant to represent a cabinet with some microphones, but not the amp. And this is really what makes me confused: in order to make cabinet to make sound, you obviously need an amp.

On the other hand, I'm pretty sure you can find impulse responses intended to represent the whole chain. For example, in this video Ola makes one.

The concept of "snapshot of the whole chain" makes much more sense to me, because as I wrote above, you need an amp to make cabinet to make sound.

So, can anyone please clarify this to me? Also I'm not quite sure how I am intended to use IR - for example, after all the effect pedals and my preamp?

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  • Since it is not possible to prevent the sonic characteristic of the amp (or mic preamp) from being part of a captured IR, the "solution" for getting "only the sound of the cabinet" is to make sure all of the other components have the most neutral sonic characteristics possible. In practice this is feasible for IRs of guitar cabinets because the amount of color added by a guitar speaker cabinet is much greater than the amount of color added by available neutral-sounding amplifiers. The qualities of the amp are rendered inaudible by the qualities of the cabinet.
    – Todd Wilcox
    Commented Dec 13, 2022 at 5:55

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An Impulse Response is anything you want it to be.

It's a convolution 'map' of an output for a given measured input. It can be anything from a simple mono impulse of a telephone or portable radio, an amp alone or amp & speakers with a specific mic in a specific room in stereo, right up to a 10s reverb in a warehouse… in 5.1 surround.

Google 'impulse reponse generator' for many ways to make them yourself. I've never tested any of those results, as I have the one supplied with Altiverb

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  • Did I understand your answer correctly - if it is a map of an input to some system to its output, than in order to create a response of a cabinet you need a generator capable of generating a signal suitable for the cabinet, and a mic(s)? And that is the way to exclude an amp from an equation.
    – Alexey Malev
    Commented Dec 12, 2022 at 10:44
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    It's the 'difference' between the input & output. How you record it depends on the result you need. Recording a guitar amp alone, you'd use direct input & output, no mic at all, of course. To record just a cab you'd need a truly clean power amp input to not affect your signal, & appropriately-placed mic[s] to record the result. To get just the cab without the room it's in, you'd need a very dead room. To get the full volume gamut as well as frequency spectrum you need several IRs which you then interpolate so the result changes with volume too.
    – Tetsujin
    Commented Dec 12, 2022 at 10:55
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    -1, there are lots of things that an impulse response cannot capture. Including most guitar pedals (distortion, tremolo, autoharmonizer, compressor, etc etc)
    – Edward
    Commented Dec 12, 2022 at 18:50
  • @AlexeyMalev I'd suggest asking a separate question about how to capture an IR.
    – user1079505
    Commented Dec 12, 2022 at 23:50
  • @Edward - the very first convolution process I ever heard was in the mid 90s when someone was demoing a prototype of this type of modelling in my office. It was a guitar amp - we had to go out to lunch while it processed, but it did it. I honestly don't know the difference between that and an 'IR' mathematically. [It turned out the guy's idea wasn't patentable, so we 'borrowed it' - the rest is history :\
    – Tetsujin
    Commented Dec 13, 2022 at 19:40
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The impulse response can represent any linear time invariant parts of the signal path. In practice this means frequency response and delay, so it is good representing room response and equalisation, and cabinet and microphone response as long as they are not driven to distortion. On the other hand, it is not suitable at all for representing distortion and modulation effects.

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