Homemade impulse from my own MESA/Boogie gear!

[jsd1982]

Greetings fellow guitar-tone enthusiasts!

For the impatient, HERE IS THE IMPULSE FILE.

In a response to Brandon's recent post on impulses... I was intrigued and read further into the subject on creating your own impulses.

What I've done here is followed the exact step-by-step instructions from that post and created my very first successful and extremely (IMO) accurate impulse from my own gear!

The gear I used to generate this impulse:

MESA/Boogie SimulClass 2:90 power amp:

• MODERN mode enabled
• Both A & B volumes and presence knobs at about 1/2

MESA Traditional 4x12" speaker cabinet with Celestion Vintage 30s (slanted top):

• Run in stereo from the 4 ohm output pair on the 2:90
• Miked with 2 Shure SM57s, in-phase with each other
• One mike pointed at the lower-left speaker
• One mike pointed at the upper-right speaker
• Both mikes point towards the left at the cone
• Both mikes are center-aligned with the dustcap
• Both mikes are about 2-1/2" away from the dustcap (can't get much closer than this due to the grille)

Step-by-step process:

1. Hooked up a stereo output pair of 1/4" jacks on my audio interface to the inputs on the 2:90 power amp connected to the 4x12" cab
2. Generated the test tone sweep WAV at 48kHz 24-bits for a length of 3 seconds
3. Attenuated the direct output of the tone sweep to -24dB so as to be just loud enough to where the signal does not distort
4. Simultaneously played back the tone sweep and recorded the miked sound
5. Exported this simple recorded clip to a WAV file at 48kHz, 24-bits (same settings as tone sweep WAV)
6. Opened Voxengo Deconvolver and processed the recorded clip WAV with the settings "MP Transform" and "Normalize to -0.3dbFS" enabled.

To test my impulse's accuracy against the real miked signal from the gear...

I hooked up the direct stereo output (NOT the record output) of my TriAxis guitar preamp to a stereo input pair on my audio interface and recorded a test clip.
I sent the raw preamp signal clip out to the power amp and speaker cabinet and recorded the miked signals.
I then used Alien Connections ReValver MkII's speaker convolution plugin with the impulse and ran it on the raw preamp signal clip and exported that to another clip.

Test results:
Raw preamp signal (very fizzy/buzzy, but this to be expected because it's the speakers that clean up all the fizz/buzz)
Miked sample direct from the gear (normalized to -3dB)
Impulsed sample clip (normalized to -3dB)

I think these are absolutely stunning results! The accuracy of the impulsed signal compared with the real gear's miked signal is pretty bang-on. Granted, the impulsed version takes off a bit of the edge and harshness that the miked signal delivers. Honestly, I rather prefer the impulsed to the miked signal!

NOTE: The delay effect is buried in the preamp signal because it was in my TriAxis effects loop. I did not post-process these clips at all except to normalize their amplitudes for a decent listening volume.

Surprisingly, the max amplitudes directly recorded / processed from the gear / impulse (respectively), were only off by about 2dB, but I attribute that to my own fault. I created the impulse with a test tone sent out at -24dB while my raw preamp signal was coming in at about -22dB (max).

[djemass]

Awesome !!

Congrats, this A/B test is pretty convincing. I chatted today with Marco Sfogli (James LaBrie's guitarist) and he was quite impressed by your demonstration.

[jsd1982]

Awesome !!

Congrats, this A/B test is pretty convincing. I chatted today with Marco Sfogli (James LaBrie's guitarist) and he was quite impressed by your demonstration.

Wow! That's pretty cool! How do you know Marco?

[djemass]

Wow! That's pretty cool! How do you know Marco?

Hi,

In fact I sent your link on his forum.

link is here:
Guitar cab impulse - Marco Sfogli Forum

For your info, this is how he mics his gear for Andromeda song:

Quote
Hi Djemass,
Andromeda on the record is the Studio Preamp + 2:90 (and a Mesa 4x12 standard cab). If I recall the lead track was two mics, an SM57 slightly off axis and a Sennheiser E906 on axis (blended together), that's pretty much a staple technique I use when it comes to recording. Yes I use an harmonizer for the live gigs, specifically an Eventide Eclipse (which I use mainly for reverbs and some delays too). There are no plans for a transcription book, would be great but dunno who would be interested in doing it!
Marco
Unquote

Cheers

Djemass

[brandondrury]

GREAT POST!

First of all the impulse sounds BAD ASS! There is no appreciable difference between the two in regard to lead tone. With that said, I would have preferred a rythm track. This is what seperates the gear in regard to tone, harmonic content, etc. I find that great lead tone is more dependent on the player. Eddie Van Halen playing lead even sounds awesome through a Rockman (so does Tom Schultz, he just sounds like shit when he plays rythm).

Let me make sure I understand what you did here. Do you mean that you recorded the direct out of your Triaxis (in fizzy mode with no emulation) and processed it with your impulse (which simulates your power amp, speaker, and micing rig)?

If so, what would happen it you had taken an impulse of the Tri-Axis, Simulclass 2:90, speaker, and micing rig? Would that provide usable results? I'm just curious. I guess it would require a reamping device to get original impulse signal into the amp, and the tone controls would be fixed. I guess it would also depend on if the impulse "reacts" the same way as a guitar does specifically in regard to how hard the strings are strummed.

I'm very new to this direct guitar crap but I'm starting to see how the technology is ready for the prime time.

Brandon

[djemass]

GREAT POST!

First of all the impulse sounds BAD ASS! There is no appreciable difference between the two in regard to lead tone. With that said, I would have preferred a rythm track. This is what seperates the gear in regard to tone, harmonic content, etc. I find that great lead tone is more dependent on the player. Eddie Van Halen playing lead even sounds awesome through a Rockman (so does Tom Schultz, he just sounds like shit when he plays rythm).

Let me make sure I understand what you did here. Do you mean that you recorded the direct out of your Triaxis (in fizzy mode with no emulation) and processed it with your impulse (which simulates your power amp, speaker, and micing rig)?

If so, what would happen it you had taken an impulse of the Tri-Axis, Simulclass 2:90, speaker, and micing rig? Would that provide usable results? I'm just curious. I guess it would require a reamping device to get original impulse signal into the amp, and the tone controls would be fixed. I guess it would also depend on if the impulse "reacts" the same way as a guitar does specifically in regard to how hard the strings are strummed.

I'm very new to this direct guitar crap but I'm starting to see how the technology is ready for the prime time.

Brandon

Making an impulse of a preamp doesn't give good results because an impulse works like a kind of linear snapshot of a signal. Preamp signal is so much non-linear: according to picking attack, harmonics may vary a lot.

Cheers

Djemass

[brandondrury]

That's what I figured. Damn! That would take a major technology boost to be able to react to dynamics of the playing. I was really hoping to replace some amps with plugins.

Brandon

[roxolder]

GREAT POST! Great IMPULSE!

But which preamp settings (all cnobs and switches) used for recording impulsed demo?
Need same spectral response from my MESA/Boogie preamp.

[jsd1982]

GREAT POST! Great IMPULSE!

But which preamp settings (all cnobs and switches) used for recording impulsed demo?
Need same spectral response from my MESA/Boogie preamp.

Why do you need to know my TriAxis settings?

Just plug the direct output (not record output) of your preamp into your soundcard line-in (preferably you have line-level inputs and a decent DAC) and run the impulse on that in realtime.

It should work with whatever preamp. You could even try it with the dry guitar signal if you wanted.

I'll be trying to make some new impulses soon since I've changed my recording setup a bit.

[roxolder]

Why do you need to know my TriAxis settings?

Just want get same sound. Because is best starting point. But most natural sound can be only with preamp settings which used by you for demo recording. (Sorry for my bad english, i`m from Kamchatka). So please get this settings, if it not so hard.

[adorian]

That is quite interesting, so in essence you created an amp/speaker sim!

[xBTWATWDx]

That is amazing. Something like this is exactly what I have been looking for! How does it work? Can it be used as a VST plugin for cubase?

are the distortion and the delay part of the impulse?

[JHERCULEES1]

This is the best impulse cab I have heard so far and the one I have been using with my mesa studio pre.
I actually stumbled on it , then read what gear you use and Im using almost the same setup , I have a triaxis and a studio pre and use them both ,
through this cab sim , it sounds great ,great job!


Justin

[xturbox]

I just start getting into this. But in short, the impulse technique is a convolution. It means when you take an original signal and shape it with a response function/impulse that was obtained from deconvolving the test signal. It can replace the cabinets+mics in guitar modeling plugin to finish processing the poweramp (Line6 GearBox, Revalver, etc) signal. Basically the scheme is as following DI--> guitar amp plugin --> impulse for cabinet modeling. Or at the third step one can use convolution reverb after the cabinet model in Gearbox or Revalver. I guess that if you have a good head you can directly output it into DAW and then make use of a good impulse as a cabinet to avoid problems with mics. Also, if someone has a good gear one can easy create a response function/impulse using the procedure described above. Impulses worth to mention are by GuitarHack, Alu, and the guy from Recabinet. More info Impulse FAQ

[adorian]

I can hear a few fellow engineers losing their jobs as you guys speak

[alex_a]

-24dB

Hi. Could you record the impulse close to 0 dB for better resolution in your preamps and especially A/D converters? (There's no problem lowering output in your convolution plugin.) It would definitely make a quality difference.

[willj]

I have all the same gear too plus doubles. Identical. It sounds to me like you used the outputs of the triaxis and not the recording outs on the triaxis.

The recording outs cut all that high fizz hence the name.

Not trying to dismiss yr hard work and i do appreciate the effort but i would be a little let down if my rig sounded like this. It falls short of what i have grown to expect from my guitar sound.

Dont get me wrong, there have been time when ive been dissappointed in my own sound as well.

[alex_a]

Hi. Could you record the impulse close to 0 dB for better resolution in your preamps and especially A/D converters? (There's no problem lowering output in your convolution plugin.) It would definitely make a quality difference.

OK, sorry, I talked shit. The impulse is full scale, I just didn't bother to look before posting. Good impulse, thanks.

[alex_a]

Generated the test tone sweep WAV at 48kHz 24-bits for a length of 3 seconds

Hi, jsd1982.

Your impulse is really cool and I played with it a lot, comparing to both of your samples. There is something in the topmost frequencies that make impulsed sound somehow flatter (you say you like it, no prob I'm just thinking of how to get to the original as close as possible). You can see it even in mp3's bitrate. You probably encoded clips with the same VBR quality, but impulsed came out 125kbit/s vs. 193kbit/s miced.

I got a couple of ideas to try. It would be great if you are interested, cause I don't have the gear you are impulsing in the first place

1) How about just record a real impulse through the cab, not a sine sweep? At a decent sample rate like 48k and higher one full output sample in a row of zero samples would be a pretty good approximation of an ideal impulse. (For example, I don't hear any noticeable difference when I play through such an impulse in Pristine Space.) The recording gear has pretty good transient response by itself, so it probably won't induce noticeable problems in the chain. But this way we are throwing out the whole deconvolution algorithm out of the equation, so the difference will probably be and might be good.

2) Anyway, I suppose it would be better to use 96k sample rate. We can always downsample the resulting impulse file anyway.
If using a sweep, longer time sweep would probably be much cooler, giving more resolution for your deconvolver.

What do you think about all this? Would you like to try it and share?