How to create an impulse

Speaker Cabinet Impulses
Drakkar
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Re: How to create an impulse

Postby Drakkar » Fri Mar 19, 2010 3:19 pm

ok grazie

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op76
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Re: How to create an impulse

Postby op76 » Sat Mar 20, 2010 7:26 am

Is there any perfectly flat test tones out there, or does convoler make necessary adjustment, no matter what test tone is used. At least izotope ozones spectrum shows, that sine sweep has awful lot more lows than highs. Pink noise is better, and white noise has few dB's more highs actually. Radio white noise has bit more mids, and lows and highs are quite flat.

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Alu
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Re: How to create an impulse

Postby Alu » Sat Mar 20, 2010 10:41 am

It doesn't matter what tone you're using.
The convolver will extract the IR by comparing the test tone and the processed one, so, whatever signal you use (as long as it covers all the audible frequencies), you'll theorically end up with the same result... but there could be some small really differences...

Anyway, I've read that there are good reasons to use a sinesweep instead of anything else.

Also, the sinesweep is totally flat, why would you say it has more lows? Did you take account that the spectrum analysis you're seeing in Ozone is logarithmic and not linear? It's normal to see a bigger wave on the lows than on the highs, it's a matter of scale...
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op76
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Re: How to create an impulse

Postby op76 » Sat Mar 20, 2010 12:42 pm

Thanks for that information. I almost guessed, that Voxengo Deconvolver (now it's right :) ) don't care about different test tone, because differents really are that "minimal"...but yet audible.

But I don't understand what do you mean about logarithmic or linear scale affecting here... Doesn't they just affect "horizontal scale", where are frequencies? So if tone is perfectly flat, it should look flat (+/-0dB line) with logarithmic or linear scale? I don't have any other freq analysis tool, so I can't do a test.

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Alu
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Re: How to create an impulse

Postby Alu » Sat Mar 20, 2010 2:46 pm

I wasn't sure about what you were refferring to, I thought that you meant the size (not the height) of the "bell" you see moving from left to right when you play the sweep and monitor its frequency response...
Being the scale log and depending on the analysis tool you use, you may see a bigger bell on the lower frequencies and a thinner one on the higher...

If you try Voxengo SPAN (the first version, 2.0 is a bit different and I'm not using it) and set the "Block" and "Speed" to max, you should see that the "bell" is always peaking at more or less the same amplitude, so it should be flat...
Even if it's not, anyway, it doesn't make a difference.

Hope it helps.
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ronaldpassion
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Re: How to create an impulse

Postby ronaldpassion » Mon Apr 19, 2010 5:47 am

Hi ALu,

i learn your instruction step by step making convolution using voxengo deconvolver.

- Create Sine Test Tone, 44.1 KHz, Mono, 0.01 sec.
Like your instruction, 12 sec, is it should be 12 sec? any reason?
- With 0.01 sec sine sweep, i open my daw, in here i try with software.
- load the sine, choose and adjust software and render with 44.1 KHz and mono with length 0.01 sec too.
- open voxengo deconvolver, load sine test tone and load the last render one.
- and GENERATE it.

Question: why should i use SILENCE equal to my sine test tone length?
IF dont put silence, it is different.
Or is it because demo version?

I just want to make 512 IR length... for CABINET like Re-Cabinet (only 512 sample)

Please correct and help me

TQ,RP!
~Revolution Your Mind~

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Alu
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Re: How to create an impulse

Postby Alu » Mon Apr 19, 2010 8:11 am

You don't have to put silence long as your test tone, you have to put silence long as you want the resulting IR to be.
Example: you're using a 12s sinesweep and you want a 512 sample IR
- Generate the test tone (12s sinesweep, let's say 44100Hz)
- Record the test tone through the cabinet

Now, you're supposed to have 2 tones of EQUAL length (12s).
If you want a 512 point IR, you need to add 512 samples of silence at the end of the processed tone (the one that was run into the cabinet and recorded).
512 samples at 44100Hz = (1/44100)*512 = 0,01161 seconds.

So you have to add 0,01161 seconds of silence at the end of the processed tone, which means that the total length of the processed tone is supposed to be 12,01161 seconds.

Deconvolve using Deconvolver and you're supposed to have your 512 IR.

Another way (which is better, considering the delay that's going to be added in the recording process) is to add something like 1s of silence, deconvolve and edit the resulting IR (which is now supposed to be 1s long) cutting everything above 0,01161s.

It's obvious that a 512 point IR is less accurate (and so different sounding) than a 1024 or 2048 samples IR.
I always suggest at least 1024, while more than 2048 is often useless...

Hope it helps
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ronaldpassion
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Re: How to create an impulse

Postby ronaldpassion » Wed Apr 21, 2010 2:54 am

Houw yeah alu,

THANKS, you are right.

Because at this time i am not trying to capture the hardware one, i just generate 0.01 second test tone.
Load in DAW. Render the software that i am trying to impulse with 0.01 second length.
Load the render into DAW again (the length become twice of the test tone one) and like you said ADD silent (AFTER) (in here 0.012 second/+- 512 sample). Render again.
Open voxengo deconvolver and generate it. DONE! Like i wish...

A question, for hardware. Is it must be 12 second test tone? any reason of this?

You are right, for enough clear definition from hi to lo freq must be 1024 and max excellent enough coloration at 2048 sample. Bigger than that is useless. But for main curve 512 could be handle too.

In my opinion, if IR longer -> More artifact capture or more defintion and also clear LO freq.
Less IR (<= 512 sample) -> Less artifact capture or less definition and LO freq becoming flat.

TQ,RP!
~Revolution Your Mind~

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Alu
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Re: How to create an impulse

Postby Alu » Wed Apr 21, 2010 7:36 am

ronaldpassion wrote:A question, for hardware. Is it must be 12 second test tone? any reason of this?

Not really, but I would not use too short test tones... let's say between 3s and 12s should be fine.
ronaldpassion wrote:In my opinion, if IR longer -> More artifact capture or more defintion and also clear LO freq.
Less IR (<= 512 sample) -> Less artifact capture or less definition and LO freq becoming flat.

Yeah, that's right, expecially for the low frequencies.
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alex_a

Re: How to create an impulse

Postby alex_a » Sun May 23, 2010 8:06 pm

Hi, Alu.

You say you don't like using click because deconvolver doesn't like short signals. But I wonder why with a click we would deconvolve anything at all? You record an impulse response of your system as it is. Did you try to use this processed click as an impulse wav? Of course, there is some non-linearity of the system captured in this file, but I think a good convolver won't see it (I suppose in theory it shouldn't). After all, if you click your amp at the same input level as your sine wave without noticeable distortion, the click won't gather much non-linear thing either.

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Alu
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Re: How to create an impulse

Postby Alu » Sun May 23, 2010 9:53 pm

Theorically, if you use a click (with click I mean a Dirac, which is a spike of amplitude 1 and length 0), you should not even use a deconvolver.
If you capture the the click response, you're sending a Dirac through a system, so the recorded signal is already your IR.
Putting that IR in your impulse response loader is supposed to work the same as the classic method (sending a sinesweep, deconvolving and using the deconvolved IR...)

I didn't try it, but it's supposed to be so...
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Re: How to create an impulse

Postby strangedogs » Sun May 23, 2010 11:52 pm

Geesh... I have trouble setting my VCR - you guys sound like scientists :lol:
"well boys there's 1 more thing you're gonna need to make it in Rock & Roll besides all those Guitars and Amps and Drums and stuff - it's called A SONG..."

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Re: How to create an impulse

Postby Adji » Sat Aug 14, 2010 11:50 pm

I'm not sure I understand it but I'm gonna try giving it a go this week and see if I can sample some of my cabinets. If they turn out well I will post them.

This is an interesting topic.

nezvers16

Re: How to create an impulse

Postby nezvers16 » Fri Oct 01, 2010 10:53 am

I like amp impulses but i want to make impulse of distortion, but you mentioned that in this way it is impossible. How can i make emulation of my Boss metalcore pedal?

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Alu
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Re: How to create an impulse

Postby Alu » Fri Oct 01, 2010 11:27 am

Learn electronics, learn C++, learn DSP and create an emulation...
That's the only way.
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Re: How to create an impulse

Postby punkster » Mon Oct 04, 2010 5:44 am

When you get this I'm gonna send you a few distortion pedals to create "distortion impulses". That would make my recording sessions a lots easier (Reamping at night gives a lots of problem with the police ;) )

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Re: How to create an impulse

Postby sacrifice__ » Sat Oct 30, 2010 8:04 am

I have Mac osx so I can't use Voxengo Deconvolver.. Have you guys something alternatively?

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Re: How to create an impulse

Postby nexis » Thu Nov 25, 2010 3:06 am

Maybe someone can help me with this one. I hear that it is possible to create an Impulse Response from using a small clip of ""guitar only" chunk of audio from a CD and taking this wav clip and using Voxengo Deconvolver. Anybody here know how to accomplish this?

nexis

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Vietnam09
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Re: How to create an impulse

Postby Vietnam09 » Sun Feb 20, 2011 7:12 pm

its so nice we can use deconvolver on windows :mrgreen:

Davka

Re: How to create an impulse

Postby Davka » Mon Mar 28, 2011 11:57 am

punkster wrote:When you get this I'm gonna send you a few distortion pedals to create "distortion impulses". That would make my recording sessions a lots easier (Reamping at night gives a lots of problem with the police ;) )


Have in mind that you have to create an impulse for every possible setting if you want to capture all the sounds in a pedal. I'm not 100% percent on this but I suspect they use mathematical models of ideal components and such when they create models of pedals, thus the term "modeling".

EDIT: Alu already mentioned this it seems :D .

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Grebz
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Re: How to create an impulse

Postby Grebz » Tue Mar 20, 2012 10:34 am

Hi everyone,

For those who still have doubts, here is a short tutorial about how to create an impulse. Screenshots can help.
You will also find a few personal impulses to download presented with audio demos.

Grebz
Last edited by Grebz on Mon Jul 29, 2013 9:09 am, edited 3 times in total.

Maxperience
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Re: How to create an impulse

Postby Maxperience » Sat Dec 15, 2012 10:10 am

Hi,

i´ve read this thread an still have some questions.
The site burningware (or so?) is down, where i could get the pink noise.
can anyone pls upload the noise cause i want to make som impulses of my cab mit the test tone (does 44100 hz, 96000hz ; 24 bit,32 bit make big differences?)
do i have to cut the time exactly to the 2048 samples at the end of the recorded tone?
would be kind, if anyone could answer ;)
thanks
stay tuned
Max

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sjc
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Re: How to create an impulse

Postby sjc » Sat Jan 26, 2013 7:43 pm

http://www.wavtones.com/functiongenerator.php

Try generating and dl the pink noise file. I did a 3 second one then stretched in reaper so it was 12 secs long. I think it was fine because the the impulse I made using this guide sounded pretty damn good.

~scott

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Re: How to create an impulse

Postby frostkald » Mon Feb 18, 2013 6:28 am

Hi!

Does anyone have Randall Cabinet Impulses?

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Re: How to create an impulse

Postby apalmalarrain » Sun Mar 03, 2013 3:51 am

Am I allowed to post here my results to a little change I did to the procedure? Nothing too important, but it worked well anyhow...


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