New cab IR feature or "Why I hope it didn't take too much room"

[deweime]

Famous last words... we were told the same thing about the Ultra approximately 6 months before it got discontinued...
(slaps on asbestos suit and runs for cover)

Right - I bought the Ultra since everyone was posting that there was plenty of room left for expansion....and 2 months later the II was announced...

 

[FractalAudio]

Right - I bought the Ultra since everyone was posting that there was plenty of room left for expansion....and 2 months later the II was announced...

You might want to get your facts straight before you shoot your mouth off. Here is a post from me on May 10 2011:

Cliff, maybe slightly off topic, but is there enough memory left in the Axe-Fx Ultra to include an integrated 8-band EQ into the Amp block and subsequent Global Amps? Because that is honestly one of the smartest features of the Axe-Fx II I've heard about yet. Seriously, that is a fantastic idea. Personally, I literally do not make a single patch without at least a Filter block at the beginning (to simulate hot pickups), and an Amp block with an EQ block immediately after it.

Nope. That's the whole problem. People wonder why there haven't been many firmware updates recently. The reason is the FLASH is nearly full. I've run out of tricks to find more memory. I'm reserving what little is left for amp models.

 

[barhrecords]

This wiki article is more layman than the wiki on impulse responses:

Convolution reverb - Wikipedia, the free encyclopedia

Also check out the help for the Voxengo deconvolver.

Voxengo Deconvolver Help

IIRC, the process would be, to run a test signal through the system to be captured. Then record the output.

E.g. for a speaker cabinet capture run a test sweep signal through an amplifier -> speaker -> mic -> preamp -> recorder.

Then the original test signal and the output, the recorded impulse response of the system being captured, are deconvolved.

The output of the deconvolver can be loaded into software, like the Axe Fx II. Then any signal, your Axe patch, can be run back through the convolution. This applies the original impulse response onto your signal, aka your guitar patch.

From what I gather, in firmware 3.0, the Axe II will output a test signal, a sweep. Then by hooking up a microphone to one of the Axe II's inputs, the Axe II will record the impulse response of whatever you are capturing, e.g. you stick a mic in front of your guitar cab and run the Axe sweep through that and back into the Axe.

Then the Axe II will deconvolve those two signals to produce the "IR" data that can be loaded into a patch.

This capture process is like a utility. It's not something you do when you are playing a gig. It is a utility to generate data that is loaded into a patch.

Richard

 

[VegaBaby]

This wiki article is more layman than the wiki on impulse responses:

Convolution reverb - Wikipedia, the free encyclopedia

Also check out the help for the Voxengo deconvolver.

Voxengo Deconvolver Help

IIRC, the process would be, to run a test signal through the system to be captured. Then record the output.

E.g. for a speaker cabinet capture run a test sweep signal through an amplifier -> speaker -> mic -> preamp -> recorder.

Then the original test signal and the output, the recorded impulse response of the system being captured, are deconvolved.

The output of the deconvolver can be loaded into software, like the Axe Fx II. Then any signal, your Axe patch, can be run back through the convolution. This applies the original impulse response onto your signal, aka your guitar patch.

From what I gather, in firmware 3.0, the Axe II will output a test signal, a sweep. Then by hooking up a microphone to one of the Axe II's inputs, the Axe II will record the impulse response of whatever you are capturing, e.g. you stick a mic in front of your guitar cab and run the Axe sweep through that and back into the Axe.

Then the Axe II will deconvolve those two signals to produce the "IR" data that can be loaded into a patch.

This capture process is like a utility. It's not something you do when you are playing a gig. It is a utility to generate data that is loaded into a patch.

Richard

correct.

 

[fullsizedog]

This wiki article is more layman than the wiki on impulse responses:

Convolution reverb - Wikipedia, the free encyclopedia

Also check out the help for the Voxengo deconvolver.

Voxengo Deconvolver Help

IIRC, the process would be, to run a test signal through the system to be captured. Then record the output.

E.g. for a speaker cabinet capture run a test sweep signal through an amplifier -> speaker -> mic -> preamp -> recorder.

Then the original test signal and the output, the recorded impulse response of the system being captured, are deconvolved.

The output of the deconvolver can be loaded into software, like the Axe Fx II. Then any signal, your Axe patch, can be run back through the convolution. This applies the original impulse response onto your signal, aka your guitar patch.

From what I gather, in firmware 3.0, the Axe II will output a test signal, a sweep. Then by hooking up a microphone to one of the Axe II's inputs, the Axe II will record the impulse response of whatever you are capturing, e.g. you stick a mic in front of your guitar cab and run the Axe sweep through that and back into the Axe.

Then the Axe II will deconvolve those two signals to produce the "IR" data that can be loaded into a patch.

This capture process is like a utility. It's not something you do when you are playing a gig. It is a utility to generate data that is loaded into a patch.

Richard

Does the quality of mike matter? Obviously not a $15 mike but say a 57 as compared to a Blue Studio Condenser Microphone?

 

[VegaBaby]

Correct me please if Im wrong, an IR is the Cab portion of the cab block. Once you insert a newly captured IR into your axe you still can change the mike type and placement ect...

Questions:

If you capture an IR with a mike 3' from a cabinet will you have this airy/spacial sound right from the start even if on your cab block you have the mike spacing and room size set to 0% ?

Does it matter what quality of mike you use to capture an IR?

Does the brand/type/quality of mike you use to capture the IR effect the results?

If you capture an IR with lets say a 57 and then use a UB7 COND in the block it will change the sound as if you captured it with a UB7.

Am I really going to be able to make "in my basement, 57 mike" any IRs that are better (or even as good as) any of the IRs already in the axe or available from RW or OH?

I think Im still lost just not as deep in the woods as I used to be, but than again my compass could be off, lol!


EDITED:
if an IR is indeed the "CAB" portion of the cab block
when you select cabinets in the AF you can choose between 1x,2x,4x ect... speaker configurations. how do you capture multiple speakers with an IR, obvious answer is position the mike further away from the cab, but wouldn't this give to much spacial tone to the IR ? Any time I recoded (with my limited experience) in a studio I just miked close to one speaker how do you get the sound or how does if differ between a 1x12, 2x12 4x12 ect....

Im lost again

ok... if you made your IR with a distance between mic and cab, that's how your IR is gonna sound. the length of the IR determines though how much of the "air" you hear. doesn't matter where the Axe's roomsize is set as these are additional early reflections added to the IR, or to the output of the cab block if you want.

anything you use in your signal chain will have impact on the IR. if yoy use a shitty cab and a rubbish mic...that's what you'll get since it's 1:1.

if you capture with a 57 and choose ANY mic (even a 57) afterwards, this is put on top, in addition to your already captured mic. that's the reason for the "none" mic option. think of the mic parameter as yet another EQ. however, if you use a completely transparent (reference mic, usually very expensive) to capture your IR, you can use the mic option to further shape the IR in the block.

if your IRs would be better...? I don't know...but if you love how your mic'ed cab with your 57 in your basement sounds...you could capture that and use it in the Axe without the need to mic or use your cab any longer.

right...hope that answered it.

 

[barhrecords]

Does the quality of mike matter? Obviously not a $15 mike but say a 57 as compared to a Blue Studio Condenser Microphone?

In the case of guitar speaker impulse response capture, the microphone and other parts of the signal chain, seems to me are picked to give some desired color to the sound.

Check out the redwirez or ownhammer sites. They have IR's for all types of microphones and different micing positions etc.

Richard

 

[VegaBaby]

Does the quality of mike matter? Obviously not a $15 mike but say a 57 as compared to a Blue Studio Condenser Microphone?

EVERYTHING matters. but the question is what YOU prefer. could be that this 4 dollar yardsale mic is just the trashy sound you've been looking for.

 

[barhrecords]

And if you are trying to capture the IR of just the speaker or cab with no influence from the room... and you want to get far enough away from the speaker with the mic position to avoid the close miked sound... NOW you are into some tricky stuff

These far-field IR's are difficult if not darn near impossible for mear mortals

On the other hand, It will be fun for me to use the new Axe feature to capture my own cabs, and see what results I can get.

Richard

 

[fullsizedog]

ok... if you made your IR with a distance between mic and cab, that's how your IR is gonna sound. the length of the IR determines though how much of the "air" you hear. doesn't matter where the Axe's roomsize is set as these are additional early reflections added to the IR, or to the output of the cab block if you want.

anything you use in your signal chain will have impact on the IR. if yoy use a shitty cab and a rubbish mic...that's what you'll get since it's 1:1.

if you capture with a 57 and choose ANY mic (even a 57) afterwards, this is put on top, in addition to your already captured mic. that's the reason for the "none" mic option. think of the mic parameter as yet another EQ. however, if you use a completely transparent (reference mic, usually very expensive) to capture your IR, you can use the mic option to further shape the IR in the block.

if your IRs would be better...? I don't know...but if you love how your mic'ed cab with your 57 in your basement sounds...you could capture that and use it in the Axe without the need to mic or use your cab any longer.

right...hope that answered it.

Thanks

Im almost done & sorry for the ignorance

One unanswered question, I understand how I would capture a 1x12 speaker with an up close mike but what is the method for capturing or "getting the sound" of a a 2x12 or 4x12 without moving the mike back and getting the sound of the room/reverb interfering in the capture?

ALSO

if you capture with a 57 and choose ANY mic (even a 57) afterwards, this is put on top, in addition to your already captured mic. that's the reason for the "none" mic option. think of the mic parameter as yet another EQ. however, if you use a completely transparent (reference mic, usually very expensive) to capture your IR, you can use the mic option to further shape the IR in the block.

so in the Axe Fx's stock cab blocks if you set the mike to none the Cab IR actually still has a mike emulation it is what ever mike was used to capture that particular IR in the 1st place?
I assume generally a very expensive very flat response type of mike?

 

[thunder100]

Cliff wouldn't implement this if it was gonna compromise other things. The 4x4 USB CPU issue (and plan to address it) is a perfect example.

This feature will be useless for some but indispensable for others. I have always wanted IRs of my own cabs so I can send the same cab sound direct to FOH, and have the option to use the same cab sound in studio.

+ 2

I have a Thiele EVM 12 Cab which is oak,rather then pinewood-so more sharp sounding -->now I can move it into the axe.

Roland

Downside is just I need to buy a good mic-->Suggestions?

 

[Patzag]

One of the most important aspects of an IR is the time factor.

If you consider that the IR is the recording of the "echo" of the impulse, you'll be closer to understanding the concept. Shoot a gun in a large room and record it, remove the original impulse (the gun shot) and you get the reflections of the room after the gun shot. The recording of THAT is the impulse response.

Obviously, in a cabinet, the "echo" is going to be very short and the speaker will only translate what it is able to in terms of frequency response, phase, etc.

If you were to shoot an IR of a "perfect" system, with a speaker that reproduces sound perfectly, there would be no residual sound after the original impulse and the IR would be empty.

But a speaker is imperfect, mauls the frequency response, changes the phase of various frequencies, and the cabinet has a size which changes the way the speaker reacts. And all this, over time. Even if the time is short. Like 2048 samples! Which is indeed VERY short at 48 KHz. A longer IR would be more "accurate" but would serve little purpose in the modeling of a cabinet or guitar body. I'd like to have at least 24000 samples for a large instrument like a Contrabass, but for the vast majority of cabinet applications, 2048 samples is plenty.

In a complex cabinet, with more than one speaker, each of the drivers changes the characteristic of the others not only by the change on volume that occurs in the cabinet, but by other factors such as the - to stay away from technical terms - the bounciness of the air inside the cabinet, the maelstrom of reflections inside a cabinet with 2 or 4 speakers blaring at the same time, etc.

All this gets recorded and is used to process the sound of your guitar plus amp.

In an acoustic body, what Fishman did is subtractive processing, using the piezo of each instrument as the source and recording the acoustic version of the instrument. Their IRs are designed to be used with the SAME instrument and then model the piezo sound back to an acoustic tone. Using a different source should not produce the same results.
It is possible to source the IR using an impulse or sweep as opposed to the piezo. This should result in a theoretically more generic approach to the reproduction of the sound of the body of the guitar.

I hope this is clear and helps clarify how this works.

 

[Patzag]

+ 2

I have a Thiele EVM 12 Cab which is oak,rather then pinewood-so more sharp sounding -->now I can move it into the axe.

Roland

Downside is just I need to buy a good mic-->Suggestions?

Rent an earthwork reference mic for the job. "Flat" response. Then the user can use the mic IRs in the Cab block to shape the tone as they want. These miss are too expensive to buy for a single job. So for the rare occasion, rental is more efficient.

If you can't find an Earthwork for rent, then try any other calibrated measurement microphone. My 0.02

 

[fullsizedog]

Thanks a lot Patzag its all commin together for me now!

After looking it up. something like an Earthwork Measurement mike is probably what Fractal, RW and OH use to capture their responses correct?

 

[barhrecords]

Thanks a lot Patzag its all commin together for me now!

After looking it up. something like an Earthwork Measurement mike is probably what Fractal, RW and OH use to capture their responses correct?

RW and OH use lots of different mics, as seen on their websites.

Also, if your intent is to capture a space, aka a room, then yeah the room reflections are what you are after.

But if your intent is to capture a speaker, you may not want any reflections from the room boundaries. In this case, it takes some expertise to eliminate the influence of the space where the IR is captured.

Richard

 

[Patzag]

Thanks a lot Patzag its all commin together for me now!

After looking it up. something like an Earthwork Measurement mike is probably what Fractal, RW and OH use to capture their responses correct?

I would imagine that Fractal's IRs are captured flat with an Earthworks or similar mic and that the cab block includes the various mics IRs, whereas RW and OH make multiple captures of the cabs with the mics they list on their products. Theoretically, adding a mic IR to the Cab IR should produce something very close to capturing the Cab with said mic. But results do vary, as they must, as the mic response will vary, even ever so slightly, when faced with an ever so slightly different environment.

I find the Fractal IRs quite usable, although my current favorite is an RW I downloaded for free from their website. I'm definitely planning on getting the rest after having tried that one and being so happy with it.

 

[VegaBaby]

so in the Axe Fx's stock cab blocks if you set the mike to none the Cab IR actually still has a mike emulation it is what ever mike was used to capture that particular IR in the 1st place?
I assume generally a very expensive very flat response type of mike?

yes. but it's not an emulation of the mic you hear, but the mic that was used during the IR process. if it's a total flat response mic, you won't really hear that mic since it's got no real character of its own. if it was a 57 or so, you'll hear that.

 

[viabcroce]

I've found this post by Mr. Mitchell about IR should someone want to have a deeper insight X)

 

[yek]

yes. but it's not an emulation of the mic you hear, but the mic that was used during the IR process. if it's a total flat response mic, you won't really hear that mic since it's got no real character of its own. if it was a 57 or so, you'll hear that.

+1

But to prevent "amp-in-the room-tone" discussions: it's still a close-mic'd signal.

 

[fullsizedog]

yes. but it's not an emulation of the mic you hear, but the mic that was used during the IR process. if it's a total flat response mic, you won't really hear that mic since it's got no real character of its own. if it was a 57 or so, you'll hear that.

Just curious how do you make an emulation/IR of a mike then? or how does Fractal do it? In the AF you add a mike response to your cab block so seems to me its not an IR of a REAL mike placed in front of that cab when the IR was captured, correct or is it???