A couple of very basic questions regarding IRs.....

P

Paultergeist

Inspired
Greetings,

I have a feeling that these questions are SO basic that most folks already know the answers intuitively....alas, I myself do not. Much is discussed on this forum regarding "IRs" (which I believe is short-hand for "Impulse Response.") I have tried the "Search" feature, but I want to make sure I am defining this line of inquiry correctly.

1. So.....is an IR just another way of referring to a speaker simulation? In other words, if I specify -- say -- 2 x 12 Celestian Greenback as a cab in a Pre-set, is THAT speaker simulation (in the AX8) then an "IR?"

2. Conversely, is an IR something *extra* which can be added in addition to factory speaker simulations?

3. Are IRs limited to speaker simulations, or are they speaker + cabinet, or speaker + cabinet + microphone.....(or with room parameters, etc)?

4. Would IRs extend to amp and effect simulations, or are those then solely referred to as "Pre-sets?"

There just seems to be A LOT of discussion regarding IRs on this forum, and I while I am still very early in the learning stages of using the AX8, I don't want to hinder my forward progress by being oblivious to the idea that I was not utilizing IRs......or utilizing them very effectively.

Thanks for any clarification.
 
Paultergeist said:
I have a feeling that these questions are SO basic that most folks already know the answers intuitively....alas, I myself do not. Much is discussed on this forum regarding "IRs" (which I believe is short-hand for "Impulse Response.") I have tried the "Search" feature, but I want to make sure I am defining this line of inquiry correctly.
Click to expand...
Correct. IR == Impulse Response
Paultergeist said:
1. So.....is an IR just another way of referring to a speaker simulation? In other words, if I specify -- say -- 2 x 12 Celestian Greenback as a cab in a Pre-set, is THAT speaker simulation (in the AX8) then an "IR?"
Click to expand...
It is a speaker "capture" mechanism. A specific wave form is played through a mic'd speaker and an Impulse Response is captured.
Paultergeist said:
2. Conversely, is an IR something *extra* which can be added in addition to factory speaker simulations?
Click to expand...
Yes... That is what "cab packs" contain.
Paultergeist said:
3. Are IRs limited to speaker simulations, or are they speaker + cabinet, or speaker + cabinet + microphone.....(or with room parameters, etc)?
Click to expand...
IRs are captured of speakers in a cabinet. So, they include the cab and speaker. In the past, the preference was to use "reference" mics so that mic "coloring" was not included and could be added later via mic simulations. Most IRs these days include the mic(s) "baked in"... You're paying for the IR creator's "ear" in mic technique.
Paultergeist said:
4. Would IRs extend to amp and effect simulations, or are those then solely referred to as "Pre-sets?"
Click to expand...
An IR is ultimately just a form of EQ, so not really.
 
1) An IR is one way of producing a speaker emulation by capturing its response to an impulse of energy (Impulse Response).

2) The factory speaker emulations are IRs. And yes, you can also load your own IRs.

3) An IR captures the response of the speaker/cab combination. They can also capture room response, but there are practical limits to how much room response they can reproduce without eating up a lot of CPU.

4) IRs could potentially be used for some effects (e.g., reverb) if the gear is designed to do it that way (Fractal stuff isn’t). IRs can’t be used for amp emulation, because they can’t represent nonlinear response.
 
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Technically IRs are not just EQs to emulate cabs. Depending on the length of the impulse response captured it will also reflect how a system responds to an impulse over time which allows to also model the room reverb characteristics. That's why there are IRs for reverb simulation available on the net.
 
Thank you everyone, that helps a lot.

It is surprising to me just how deep these waters can get.....after reading the (kindly provided) Wiki page, it sounds to me like someone could spend years studying / creating IRs alone. Thanks again.
 
Y
ChristThePhone said:
Technically IRs are not just EQs to emulate cabs. Depending on the length of the impulse response captured it will also reflect how a system responds to an impulse over time which allows to also model the room reverb characteristics. That's why there are IRs for reverb simulation available on the net.
Click to expand...

Yeah, this....although for the most part if you are just trying to understand what it does, you can consider it an eq.

It's also one of the biggest components of your sound, so I'd spend a few minutes checking through the IRs....Leon Todd @2112 does a fantastic video where he describes his approach to selecting them....you can set a looper to play a loop while you scroll thru cabs and narrow it down to the ones you like

If you have a real life cabinet you normally use and are familiar with it's sound, I'd also look at similar IRs, to help you get up and running quickly

Also, subscribe to Leon's channel, he's one of THE best resources on YouTube!
 
At someone else's suggestion in a post, probably on FB, I used the looper to even out levels on different amp models. Great tip, that. Saves you looking like Quasimodo and feeling like a truck hit you after hours of scrunching your shoulders up to keyboard and mouse *around* your guitar. :)

I have some IRs from RedWire that I got to add in place of some of the stock IRs in Scuffham's S-Gear, which includes a nice Weber Blue Dog in a T/S cab which I like a lot. Will try my hand at uploading them into the AxeFX III this weekend.

Will also try Leon's no-looky method and see what of the factory IRs tickle my fancy. Already found a nice 4x12 Beatle 160D that I like.
 
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