Creating impulses.....

[Glenn Fricker]

Hey guys,

So I started playing around with this impulse thing.... pretty cool. My question is, how do I record my cabinet & make my own? (might be willing to share sometime in the future)
Any help would be appreciated.

-0z-

 

[~BURNY~]

Download Voxengo Deconvolver
Install
Create a sweep file with deconvolver (12sec, mono 96khz 24 bit is a good compromise)
Mic your amp
Press rec
Run the sweep through the power section of the amp
Press stop
Deconvolve with deconvolver
Voilà

 

[theunforgiven246]

Ok guys, it seems pretty simple... it took me a few minutes to understand it, and I've tested the method "impulsing" an amplitube 2 cab... it works!

So just download Voxengo Deconvolver:
http://www.voxengo.com/product/deconvolver/

The demo version works perfectly for what we have to do, so you don't need to have a registered version (but the demo will allow you to create 3 impulses per session, so, after 3 impulses, you have to restart the program Smile )

Open Voxengo Deconvolver.

We need a "TEST TONE", basically a sine sweep containing al the frequencies we can hear... just click on "Test Tone Gen", use the default settings (24bit, 44100Hz, mono, 3 sec., DON'T CHECK "apply fade in-out for reverse" ) and click on "generate".

Create an impulse response from a real gear

Ok, now we need to route that wave file inside the Cab/Mic we want to capture... so you have to route the file inside the power amp of your head (fx-return or power-amp in) and record the cab output with the mic...
Just connect your soundcard output to the poweramp and record the mic signal (you could need 2 pc or a soundcard that allowa you to play and record at the same time... you could do that with a DAW). Beware the clipping of the Test Tone!!! It doesn't have to clip!!! Lower the volume!!!

Create an impulse response from a software sim

It's more or less the same thing, just easier!
We need to open our DAW and create a mono track, then load the Test Tone on it.
Now we have to open the VST from which we want to take the impulse response in the track insert, for example GR.
Now we have to close or bypass all the components we don't need (stomps, amps...) and activate only the cab+mic section.
Play the Tone Test now to see if it clips inside our VST. If so, lower the volume or use the "learn" function!
What we hear when we click "play" is just the Tone Test processed by the VST, and this is what we need, so export the file into a .wav file!

For both, then...

Export the recorded tone on a 24bit Wave Mono file.
IMPORTANT: when you export, remember to add a bit of silence on the end of the clip!!!

The recorded tone will be the "file to process" in Voxengo (obviously the Test Tone File is the Test Tone we have generated a while ago).

Set "Out Bit Depth" to 24 and select just "Normalize to -0.3dbFS"

Click process and you'll have a wave file in the same directory of the processed tone.
This is your impulse!

(probably you'll have to tweak the volumes to get the impulse right... so, patience!)

Hope it helps!

For any question, just ask, I'll try to help you!
Voilà

that should be enough detail to do it properly

Edit: Here's the link to the page

 

[kass]

im tempted to make an impulse of my whole set up! preamp and everything

to see how shitty it would sound

someone do it

im lazy

 

[DFGeneer]

An alternative (and perhaps more natural) way would be (provided that your amp has parallel fx-loop):

1. Plug your guitar and start your amp
2. Take signal directly after the preamp (fx-loop out) and record it as Track1
3. Take signal from the miced cab and record it as Track2
4. Play a bit while recording the two tracks
5. Add some silence at the end of Track2 (100 ms is perfect, this sets the length of the impulse file)
6. In Voxengo Deconvolver use Track1 as Test Tone File and Track2 as File to Process (Other recommended options are Out bit depth: 24 and check on Normalize to -0.3 dBFS)
7. You may want to fade out the tail of the impulse file in a wave editor in case it catches a lot of noise.

You may now want to apply the thus created impulse on Track1 to see how close it gets to the real thing recorded in Track2. Pretty damn close!

 

[deLuther]

For Voxengo Deconvolver is better not use Reversed technique and MP transform for better result (at least in case of test tone generated bu Deconvolver itself) - result is much closer to original. I also use 96k test tone and store resulting impulse in 32bit file - it seems better suited because of mathematics used. IMHO.
As I understand impulses are not well suited for preamps because of nonlinear nature of preamps - by definition convolution suited for linear systems only. So I have weird results when tried to get impulse response from my preamp.

 

[theunforgiven246]

An alternative (and perhaps more natural) way would be (provided that your amp has parallel fx-loop):

1. Plug your guitar and start your amp
2. Take signal directly after the preamp (fx-loop out) and record it as Track1
3. Take signal from the miced cab and record it as Track2
4. Play a bit while recording the two tracks
5. Add some silence at the end of Track2 (100 ms is perfect, this sets the length of the impulse file)
6. In Voxengo Deconvolver use Track1 as Test Tone File and Track2 as File to Process (Other recommended options are Out bit depth: 24 and check on Normalize to -0.3 dBFS)
7. You may want to fade out the tail of the impulse file in a wave editor in case it catches a lot of noise.

You may now want to apply the thus created impulse on Track1 to see how close it gets to the real thing recorded in Track2. Pretty damn close!

Couldn't you do this with an acoustic-electric guitar to get an impulse to make better acoustic impulses?
i.e.:
1. Plug in your guitar and mic the acoustic
2. Take the signal out from the acoustics preamp and record it as Track1
3. Take signal from the miced acoustic and record it as Track2
4. Play a bit while recording the two tracks
5-7 just as DFGeneer said?

or would that just not work/thats how they do it?

 

[DFGeneer]

^well, that may work to some extent...

The impulse "stores" the transient character of the medium that is between the two signals. So, playing an acoustic guitar through a pickup and impulse response would sound as it's been miced. But playing a solid body guitar through that same impulse would sound a bit different, since the dry signals of an acoustic and solid body guitars sound different.

On the top of that with acoustic guitar as a source it would take a bit longer to capture nice impulse response, since the "test tone" is not very rich harmonically, not even close compared to the preamp signal of a high-gain guitar amp. And the test tone signal needs to be as broad as possible frequency-wise in order to capture the response of the medium in a broader frequency range.

However, still quite doable and interesting thing to try for whoever owns an acoustic-electric.

 

[theunforgiven246]

^well, that may work to some extent...

The impulse "stores" the transient character of the medium that is between the two signals. So, playing an acoustic guitar through a pickup and impulse response would sound as it's been miced. But playing a solid body guitar through that same impulse would sound a bit different, since the dry signals of an acoustic and solid body guitars sound different.

On the top of that with acoustic guitar as a source it would take a bit longer to capture nice impulse response, since the "test tone" is not very rich harmonically, not even close compared to the preamp signal of a high-gain guitar amp. And the test tone signal needs to be as broad as possible frequency-wise in order to capture the response of the medium in a broader frequency range.

However, still quite doable and interesting thing to try for whoever owns an acoustic-electric.

Cool. Well so if someone made an impulse like this, and I recorded a track with an electric with piezo's then applied the impulse, it's sound like a mic's acoustic if done properly?

 

[deLuther]

I suppose that impulses can not store transient character, because convolution process is basicaly linear filter.

 

[deLuther]

There is one aproach that can make impulse without the use of deconvolver - just run pulse signal (one sample with value 1 or maximum) trough your amp, record this signal (length can be short) and you already have impulse. This aproach even can outperform deconvolver because there is no FFT at all. Very natural sound.

 

[DFGeneer]

^Not sure if voxengo deconvolver uses the simplified convolution method based on FFT.. All I can say it that it gives extremely good results.
And yes, the impulse response contains the transient character, that's why the impulses have certain length, otherwise they would be 0 ms long.

 

[deLuther]

DFGeneer: even EQ filters will not have zero length if convolution is used. Deconvolver manual says that it is using FFT (but exact), not including reversed method. Reversed method give the most bad result (in my case). Impulses is like reverberation by definition. Maybe we just have different meaning of "transient".

 

[DFGeneer]

Maybe we just have different meaning of "transient".

Yep, that's the source of the misunderstanding. Anyway.. I agree then

 

[Loren Littlejohn]

What do you do on mac?

 

[GuitarHack]

^^^

Generate Test-tone:
24-bit
96000
Mono
12 Seconds

Deconvolve with MP Transform ticked.

That's should be all you need.

Not sure what all that other shite is about.

.....(might be willing to share sometime in the future)....
-0z-

Feel free to change that to "Will share the results with you guys when they are done"

 

[Loren Littlejohn]

Deconvolve with MP Transform ticked.

Link? I just googled this and found alot of chemical shit...

 

[GuitarHack]

^Sorry, my reply wasn't directed at your question about how to do it on a mac. It was a general reply about using deconvolver on PC.

The ^^^ were directed at the posts above yours. They were making my head spin.

 

[Loren Littlejohn]

Oh okay .

 

[DFGeneer]

GuitarGodgt, on a mac you can try the approach that doesn't require convolution
It's the one described by deLuther in his post #11 on this thread.
However, be careful running too loud impulse through your power-amp section.