#1
What EXACTLY does this do to an amp sim guitar tone?

Is it simply EQ or is it compression also or.....?


I know it's "aimed to emulate the power-amp" of a rig and the designed to replicate the speaker movements, but really, what does this mean for the input signal?

Cheers for any responses
Everything owes its existence solely and completely to sound.

Sound is the factor which holds it together.
#2
You actually have to run it as a VST plug in while recording.
If you are running something like PodFarm or Amplitube, you would actually turn off your cab in the software so you are running just the preamp sound, which sounds nasty, and then record like that. You would then add your cab impulse in as a VST on the track that you are recording that guitar to.

Maybe not the best explanation, I just started using impulses.
#3
I meant more so how it affects that sound, what manipulations it performs, rather than how to place it into a chain haha

thanks tho
Everything owes its existence solely and completely to sound.

Sound is the factor which holds it together.
#4
For me, the sound is so much more natural. It is a more full sound than what I was able to achieve from PodFarm.
#5
Yeah, I know what it does too, but I wanna know HOW it does it. :P

Impulses are audio files, right? How do they change the sound of what I record?

(apologies for writing like a 6 year old, I've been up all night. O___o)
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#6
i dont feel like typing things out again, so here is my response to a similar question:
Quote by jof1029
lets start with impulses. this thread has a nice little bit on how to load them up and use them. you skip the amp model section, and can just load up the impulses. post one has some impulse loaders and some impulses to start with. step 4 in post 2 is where you want to start for loading them. next paragraph is technical mumbo-jumbo, skip it if you dont care.

lets start with what this impulse thing actually is, because it isnt an impulse. it is actually the impulse response of a system. in theory, an impulse is an infinitely short and infintely tall signal. in practice, it is a really short and loud click. so an impulse response is running an impulse through a system and capturing the output. what we have to understand is that the impulse response of a system perfectly characterizes it. and when i say understand, i mean just accept it because it is true (read more into it if you want though!). that means if we run an impulse through a cab and mic (our system here) and record it, we now have access to a model of that system. impulse loaders take that model and run your signal through it. which means it sounds like your guitar was run through that cab and that mic. cool, huh?


that may not be 100% what you were looking for, but it should sort of answer your question.
#7
^^^

Enlightening! really i had no idea what it was, only that it was a simulated 'cab' haha
Cheers mate!
Everything owes its existence solely and completely to sound.

Sound is the factor which holds it together.
#8
Impulses can do a lot more than just simulate cabs, they can be used for reverb of actual real places, want you to sound like you're paying in the Sistine Chapel? Go record an impulse of it.

I have a bunch of impulses from compressors, preamps, reverb units, rooms, echos and such. It's pretty cool to know that the sound you are using was actually recorded in a real place and not done with some computer calculations.
#9
Quote by Pants1985
You actually have to run it as a VST plug in while recording.
If you are running something like PodFarm or Amplitube, you would actually turn off your cab in the software so you are running just the preamp sound, which sounds nasty, and then record like that. You would then add your cab impulse in as a VST on the track that you are recording that guitar to.

Maybe not the best explanation, I just started using impulses.

The bolded part is perhaps why you shouldn't have tried to answer An impulse response is definitely not 'ran as a VST plug-in while recording'. It is a file, usually a .wav, taken of the response given by running an impulse through ________ environment. Anything importnat has already been explained, but to carry on a little - an impulse response can be the response of anything, whether it's the impulse response of a small box, a room, a speaker cab, someone's throat etc.
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#10
So its like an record of how this "impulse" would sound in a certain environment, then the impulse loader trys to manipulate it to sound like that?

hence impulse 'response'?
Everything owes its existence solely and completely to sound.

Sound is the factor which holds it together.
#11
Quote by maggot9779
Impulses can do a lot more than just simulate cabs, they can be used for reverb of actual real places, want you to sound like you're paying in the Sistine Chapel? Go record an impulse of it.

I have a bunch of impulses from compressors, preamps, reverb units, rooms, echos and such. It's pretty cool to know that the sound you are using was actually recorded in a real place and not done with some computer calculations.
This ^^

the question is, how do you actually record one?
#12
Quote by TechnicolorType
This ^^

the question is, how do you actually record one?

Is that you musing or actually wanting to know?

I'm about 85-90% sure it would be done by playing a burst of white noise through that environment and recording the output with a measurement microphone that would have a very flat frequency response, then (the bit I'm unsure of) inverting the polarity of a duplicate of the white noise track to subtract the white noise from the recorded signal and leave an 'impulse response' of how the environment would react across all frequencies to a short burst of ______. Then it is just put into an impulse response loader that will apply the impulse response to whatever you feed into it.

Bear in mind that is my theory, having never looked this up and just making (hopefully) educated guesses... I'm probably wrong but I tried!
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Last edited by DisarmGoliath at Mar 23, 2011,
#13
I was actually thinking about trying to make my own impulses the other day then realized I had no idea going about it. I feel like a deep understanding of it would allow some trippy shit to be done if you can figure out how to manipulate impulses oddly lol

Which may not make sense, but just think of a completely ****ed response you could get (I am mainly thinking this in like industrial rock/metal type music).
#14
Quote by DisarmGoliath
Is that you musing or actually wanting to know?

I'm about 85-90% sure it would be done by playing a burst of white noise through that environment and recording the output with a measurement microphone that would have a very flat frequency response, then (the bit I'm unsure of) inverting the polarity of a duplicate of the white noise track to subtract the white noise from the recorded signal and leave an 'impulse response' of how the environment would react across all frequencies to a short burst of ______. Then it is just put into an impulse response loader that will apply the impulse response to whatever you feed into it.

Bear in mind that is my theory, having never looked this up and just making (hopefully) educated guesses... I'm probably wrong but I tried!
oh, I was being serious. I wouldn't mind making an impulse of this Soldano cabinet.

I have no idea how to do what you said though. :]

Could I get a microwave impulse too?
I mean come on. How awesome would it be to use a microwave as your cabinet.
#15
Quote by TechnicolorType
oh, I was being serious. I wouldn't mind making an impulse of this Soldano cabinet.

I have no idea how to do what you said though. :]

Could I get a microwave impulse too?
I mean come on. How awesome would it be to use a microwave as your cabinet.

I know how to make them with Logic, as it has a bundled IR Utility that lets you create your own... works by sending a sweeping signal to _____ and then does some processing (similar to what I described I think, but working it out as a response to one sample rather than over the time of the sweep (as though a single sample of white noise was played). You need a microphone if you want to record anything analogue of course, and as all microphones I know are metallic you shouldn't really put one in a microwave joking aside, if you can find a small enough speaker/way to get a fairly flat frequency sound into a microwave and a mic in there (and make sure the microwave is off) you really could recreate playing through a microwave!
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#16
Quote by DisarmGoliath
I know how to make them with Logic, as it has a bundled IR Utility that lets you create your own... works by sending a sweeping signal to _____ and then does some processing (similar to what I described I think, but working it out as a response to one sample rather than over the time of the sweep (as though a single sample of white noise was played). You need a microphone if you want to record anything analogue of course, and as all microphones I know are metallic you shouldn't really put one in a microwave joking aside, if you can find a small enough speaker/way to get a fairly flat frequency sound into a microwave and a mic in there (and make sure the microwave is off) you really could recreate playing through a microwave!

If i could find a way to get a impulse of my bathroom's shower then I will be set.
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#17
that excites me.

People have joked about plugging guitars up to toilets and stuff and saying it'd sound better than an MG.

It'd be awesome to test that theory.

by the way, what's a mic you'd recommend? I don't know about the frequencies for the ones I never use.
I have like 500 mics I can use so I'm sure I'll have it if it's popular.
Last edited by TechnicolorType at Mar 23, 2011,
#18
To make an impulse, you play a very short (maybe 5ms or less) burst of white noise and record the result. Then save it and load it into a impulse loader. Simples.

Another way is to use a sine sweep instead of a burst, then use some software to make the impulse. I haven't tried that yet though.

edit, damn it, ninja'd.

by the way, what's a mic you'd recommend? I don't know about the frequencies for the ones I never use. I have like 500 mics I can use so I'm sure I'll have it if it's popular.


Use whatever you want, make a whole bunch of impulses from lots of different positions using lots of different mics.
Last edited by maggot9779 at Mar 23, 2011,
#19
but where exactly does the white noise go?

would you run it through a cabinet basically?

and if so, then how? I know a lot of DAWs can generate white noise. How do you get it to go through something else?
#20
Tech, you've got me thinking now damnit and I should be sleeping! If you placed speakers up close to the toilet seat, and used a contact mic (the kind found in drum triggers... they're quite cheap actually), with enough volume I think that's doable!

As for recommended mics... for reverbs of rooms etc. and I guess the most accurate IR, DPA make very good measurement microphones, but otherwise any condenser with a really small diaphragm will give pretty good results (you just want the flattest freq response you can get). As for cabinet IRs, depends on what you want, choose as though normally mic'ing the cab... 57's, e906, i-5 etc.
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#21
Quote by TechnicolorType
but where exactly does the white noise go?

would you run it through a cabinet basically?

and if so, then how? I know a lot of DAWs can generate white noise. How do you get it to go through something else?

Send the noise through to your main output, then interface's output(s) into amp head(s) effects return (post-preamp in other words) and run the amp as normal, and mic it up... the s' in brackets are for if you want it in stereo with multiple cabs.

As for the white noise, I believe it's filtered out how I suggested earlier to leave just the response of the source for that burst/sample.

Quote by kcorkcar
If i could find a way to get a impulse of my bathroom's shower then I will be set.

There are a few companies making waterproof mics (infact I'm sure Sennheiser do one)... DO IT!!
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Last edited by DisarmGoliath at Mar 23, 2011,
#23
ITT: I learnt that I go slightly off-the-wall when I'm sleep-deprived (like now, meh) and think of some ridiculous ways to make strange stuff possible; I make a lot more spelling/grammar mistakes/confuse myself mid-sentence; managed to get Tech excited... ahaha with talk of miking up microwaves; and double-post and edit my posts mega fast!


Also, as I'm slightly more awake and not typing on my phone screen: all you need to do to make an impulse response is to find an impulse (the white noise burst or a sweeping sine wave), run it through whatever you want the response of, and then feed it back into an impulse reader of some kind.

In Logic, assuming I was to bypass using IR Utility at first, I would open up the signal generator, and set up a sine sweep (let's say lasting 10 secs) between 20Hz-20kHz, and then take the main output of my interface (Apogee Duet) and either use just one of the L-R jacks and pan the sig. gen. that way 100%, or use the headphone out with the volume up (and the main output of the Duet muted) and run a cable from that line level signal into _____ and then if the equipment was analogue outboard gear, I'd take the output of it and put it into one of (or both if stereo) the DI/line level inputs of the Duet.

Then when I was ready, I'd hit record in Logic and capture the return feed of the impulse. Then if I used a short burst, I could invert the polarity of the track with the signal generator (in Logic Pro 8, done easiest by opening up the Gain plug-in and inverting the L-R polarity) and as long as the 'impulse response' was time-alligned properly, the original sine sweep and the sine sweep in the response would cancel out (as they would be of opposing phase*) leaving just the impulse response of the gear. If I'd used a sine sweep I would need to feed the response into some form of IR deconvolver (which I imagine would be best used as the signal generator too, which is how IR Utility works) and that would convert the response for me.

If I wanted to get the IR of a speaker cab, it's exactly the same process except you need a mic with a flat frequency response (as I've said earlier, DPA make some well-recommended measurement mics, but if budget is an issue - small diaphragm condensers generally have the flattest frequency response over the audible freq. spectrum), and you would take the output from your interface and go into your amp head's effects return ('FX In' on some amps, basically it's just the return stage of an effects loop, and means you can bypass the colourisation of the preamp entirely) and then set up the mic how you like to record as normal. Remember that your speaker cab isn't powered so plugging in the output of your interface to the speaker in of your cab will achieve nothing as your interface is unlikely to be able to drive the speaker cab and will probably be damaged considerably (although don't quote me on that ).


*For those unsure about phase, and probably most of what I just wrote - if something is perfectly out of phase with something else (called 180 degrees out of phase) it will result in a nullification of that signal... assuming the source matches, i.e a sine wave that is of equal amplitude but one is shifted along so that where one goes up, the other goes down at the same time/speed. In essence, this means that if you have a signal to start with, send it through a modifier and then invert the original source, you are able to cancel out the source signal in the modified signal to be left with just the modification (something handy to use audio engineers for many reasons).

On a similar principle, balanced microphone cables work on the basis that the signal should be exactly the same travelling through the positive and negative wires, just inverted, so any interference from the outside environment to the wires should (theoretically) be imbalanced due to the way the wire is wrapped, and this means removing interference from a balanced line is easier (the main reason why XLR has been the standard mic cable for a long time, as opposed to using a mono jack to jack).


Edit: Apologies for the wall-of-text... I'm rambling in my old age lack of sleep
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#24
as a note, you dont always want a microphone with a flat response. the microphone is part of the system, so if you stick a sm57 on your cab, you are also capturing the sm57's response. you end up not just modeling the cab, but the cab miced up. for things like capturing a room for reverb i imagine a flat response mic is best, but i wouldnt really pick that for making a cab impulse.
#25
btw a cabsim is just an EQ with like unlimited bands? (and the IR file "controls" the gain of the bands)
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#26
Quote by Daneeka
btw a cabsim is just an EQ with like unlimited bands? (and the IR file "controls" the gain of the bands)

In simple terms - near enough, except it's to do with time domain as well as just EQ changes, like how the cab resonates after a signal passes through.
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