Making own impulses

A

Andrew07

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Nov 5, 2006
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I know this has been covered, so I apologize but I plan on doing this so I can share it with all of you! so peace :) . Im going into a studio this weekend with a Marshall 4x12 with greenbacks, a mesa 1x12 with a black widow and a vox ac30 with blue alnicos. Also a Rosetta 800 going into a 002, Royer 121, SM57, Chandler TG2 and a Great River MP2NV.

Ive seen an altiverb document explaining how to make impulses but I can't seem to find it (Im using Altiverb 6.1x now).

What kind and how many impulses should I try to get? Center, edge, how many '' back, etc? What about finding the sweet spot on the amp? Do the whole: turn amp on, touch end of guitar jack so the amp is buzzing, find the most equal spot by ear?

www.cherryhillrecording.com/zip/VoxAC30.zip
 
Generate a sweep tone. Record the tone through your poweramp and cabinet of choice. Deconvolve the resulting file.

Voxengo Deconvolver may be of interest to you if your using a PC. It's also capable of generating the tone you will need.
 
You can as well play a bit your guitar (few seconds) recording two tracks simultaneously: one direct out of the amps preamp (fx loop send) and second the miced cab.
Then add 100 ms silence at the end of the miced track and deconvolve them using voxengo deconvolver.

This technique is similar to the one with the sweep tone, it's just that instead of a sweep tone you use the tone of your preamp. Of course using high-gain distortion is better since the "test" tone has richer frequency content.
 
My suggestion:

1. Dead center. Between Center and Dustcap. Edge of Dustcap/cone. An inch from Dustcap. Mid cone. On and Off Axis. All positions have a "Sweet spot" where they sound better, so spend a minute getting that. Could be against the grill, or a couple of inches away.

OR: Find the sweet spot and just do them. ;)
 
I have an intel macbookpro tiger running cubase 4 and pro tools 7.3

Not sure what deconvolving is. Since the sine test only takes a second I'll try to get a bunch and you all can tell me which are crap
 
There is one aproach that can avoid deconvolution, but it lacks some high frequencies.
You can send pulse signal (one sample at maximum followed by silence) and record response (This is according to fundamental definition of impulse in many books on DSP).
That response will be your impulse.
And another one shortcoming of this technique - I can`t get good sound with mic placed further (to some extent) from grile.
But for close micing it is not bad.
 
Altiverb has a sine sweep generator that I'll use, and maybe I can just post up those files on my FTP and someone with a PC could deconvolve them?

I really like GuitarHack's impulses- does anyone know how he got his? Listening to the impulses you just hear this little pop-is this the result after deconvolving, or is he using a "sample tick" to get his impulse response rather than a sine sweep?
 
GuitarHack`s impulses made with Voxengo Deconvolver (if I am remember right).
So post your responses for deconvolution.
Maybe better to use test tone generated by deconvolver... but it can use any test tone (this also must be posted).
And better to use 24bit files for record. If it is possible try different rates - i.e. 44.1 and 96k.
 
the altiverb sweep generator has a ton of options: 10 second or 30 second sweep? 3, 7, or 16 seconds of silence?

i put up the 10 and 30 second sweeps with 7 seconds of silence on soundclick so you guys could tell me if its ok or not

soundclick.com/andrew0786
 
So we're about to start...and I realized Im still not quite sure what to do :p

What powers the cabinet? Is the amp head? Won't its settings effect the sine wave? I have a 1/4'' output coming off of a Digidesign 002 which is sending the sine sweep
 
Andrew07 said:
So we're about to start...and I realized Im still not quite sure what to do :p

What powers the cabinet? Is the amp head? Won't its settings effect the sine wave? I have a 1/4'' output coming off of a Digidesign 002 which is sending the sine sweep
Click to expand...

I believe you send the the signal to your amp's effect's loop return. So you're basically using your amps power amp only and not the preamp. So you're actually getting an impulse of a power amp, cabinet, speaker, microphone, and position all at once.

If I'm mistaken, someone please correct me.
 
Nope, that's it exactly (except that you also get the character of the mic preamp included in the impulse as well)
 
I've never heard that cab, so I don't know if it sounds ok.
I find it fizzy, but considering that's a 1x12 it could be possible...
Is a closed back or open?
Did you take the impulse using multiple mics at the same time? If so, beware the phasing issues
 
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