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Axe-Fx III Firmware Version 11.00 Public Beta

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Intheband

Inspired
So basically your saying we have to take note of the cab on every preset, reload the amp, then reset the the cab if it changes to what it was before, then save the preset, for all 500 presets?
 

Intheband

Inspired
Who said that? You don't HAVE to do anything and you presets will sound exactly as they were before.
The way I read your note, no presets are changed until you reload the amp. When you do that, there is a chance that the cab has changed, so If you want the preset to have the same IR, you need to keep the original. ( which will now have the new parameters , correct?)
don’t worry, just me trying to picture how this is working. I’ll get it eventually😆
 

FractalAudio

Administrator
Fractal Audio Systems
Moderator
The way I read your note, no presets are changed until you reload the amp. When you do that, there is a chance that the cab has changed, so If you want the preset to have the same IR, you need to keep the original. ( which will now have the new parameters , correct?)
don’t worry, just me trying to picture how this is working. I’ll get it eventually😆
Selecting an amp does NOT change the cabinet IR. It changes the speaker impedance model. Two very different things.
 

2112

Fractal Fanatic
I played so much guitar with this FW that my finger tips are absolutely shredded, which hasn't happened in a long time! The tweaks to the Recto's mentioned in the release notes are real nice too.

I'm working on a idea to use the outputs of the Axe-Fx directly along with a special cable to allow field measurements by users.
This combined with the existing TM/IR facilities would be absolutely next level!
 

Joe Bfstplk

Power User
In retrospect perhaps I should've updated the amp blocks to use the new impedance curves. It sounds better and the average user probably wouldn't care about the change in the sound of his preset.
Maybe a "convert all speaker impedance curves" setting hidden somewhere in the global settings that hides after one use? I imagine the number of people who have touched this impedance curve is fairly small, so the old defaults are likely still set at factory settings....
 

200man

Experienced
Maybe a "convert all speaker impedance curves" setting hidden somewhere in the global settings that hides after one use? I imagine the number of people who have touched this impedance curve is fairly small, so the old defaults are likely still set at factory settings....
the bigger problem for me is experimenting with cabs...there are plenty in the axe and as i preview the different cabs, if i could get the default response behavior loaded in the amp block automatically...i could rifle thru authentic sounds much easier!
 

vin156

Member
Used the AC20 with AC20 IR and AC20 curve this morning with the band. Holy smokes it sounds amazing with my old telecaster!
I thought the AC20DLX Speaker Cabinet sounded kind of muddy & took away from the beautiful sparkle. Set the LF Res Q (1.787), LF resonance (5.83) & HF resonance (7.5) back to factory patch default & it sounds amazing. Even after those changes, it shows a different speaker graph in the speaker page of Axe edit compared to the factory patch default.
 

DreDawgie

Member
No.

A tube power amp is a transconductance amplifier, voltage in - current out. A speaker is a voltage transducer, voltage in - sound out. Since the power amp is driving current the voltage at the speaker is the current times the impedance of the speaker (Ohms law V = I*R). The voltage therefore is dependent upon the impedance.

A solid-state power amp is a voltage amplifier, voltage in - voltage out. Since the power amp is driving voltage the voltage at the speaker is NOT dependent on the impedance of the speaker.

When an IR is captured (correctly) it is done using a solid-state power amplifier so the effects of impedance do not influence the measurement. Some people try to use tube power amps to capture IRs. This is incorrect methodology.

The Axe-Fx power amp simulation is a transconductance simulation. It uses a simulated speaker impedance to derive the output voltage that then drives the simulated cabinet (IR).

Firmware 11.xx has 47 (and counting) speaker impedance curves that you can select that allow for different power amp transconductance responses. Moreover the impedance simulation is now a high-order network that simulates the perturbations in impedance due to cabinet resonance.

If you are using a conventional guitar cab and solid-state power amp ideally you would want to know the impedance curve of the cabinet. This requires special test equipment although I'm working on a idea to use the outputs of the Axe-Fx directly along with a special cable to allow field measurements by users. At this time the impedance curve matching is a Matlab program though and requires some hand-tuning.
Thanks for the explanation, I was similarly lost as the poster. I'm still slightly confused. Isn't the cabinet literally just a physical filter of sorts... the sound is based on the impedance of the speaker as well as the physical construction of the cabinet, right? So when you say cabinet resonance, that's the effect of the physical part of the cabinet, like the way the wood resonates or absorbs sound at certain frequencies? How does that affect the impedance? So for the most realism, this is all assuming we use the correct IR for any of this to matter? In a perfect world, shouldn't there be a dedicated speaker impedance curve for every IR that comes with the Axe FX?
 

rickboot

Power User
In a perfect world, shouldn't there be a dedicated speaker impedance curve for every IR that comes with the Axe FX?
Ive been thinking the same thing. Why not embed metadata into an enhanced speaker IR that includes impedance, resonance, mic, amp info. Then let the Axe-FX configure the amp.
 

FractalAudio

Administrator
Fractal Audio Systems
Moderator
Ive been thinking the same thing. Why not embed metadata into an enhanced speaker IR that includes impedance, resonance, mic, amp info. Then let the Axe-FX configure the amp.
Ideally an IR would contain two IRs: one conventional IR and one that represents the impedance. But the average IR producer has no idea how to capture the second one.
 

Joe Bfstplk

Power User
the bigger problem for me is experimenting with cabs...there are plenty in the axe and as i preview the different cabs, if i could get the default response behavior loaded in the amp block automatically...i could rifle thru authentic sounds much easier!
The problems with that are fourfold, at least:

1. Not all of the cabs each have a curve in the list.

2. Additionally, any 3rd party cabs can't be predicted by FAS, so their impedance curves are not going to be available in the Axe.

3. The cab block would have to trace backwards from its input to detect which amp block it is downstream from in order to even know which amp block's impedance curve to switch, as the impedance curve is stored in and used by the amp block, to determine how the amp responds to its load.

4. The cab block can hold multiple IRs in parallel. The curves for the combination are not likely to be in the list. See #1 and do some statistics/probability math to find how many different combination curves would need to be available, given the huge number of even just factory cabs that could be loaded in each slot. That's a LOT of curves. Calculating a curve and applying it might be possible if all the cabs had curves, but, as mentioned in #1, they don't.

I think the best we can hope for is to choose an impedance curve for a similar cab and use that.
 

Joe Bfstplk

Power User
Ideally an IR would contain two IRs: one conventional IR and one that represents the impedance. But the average IR producer has no idea how to capture the second one.
This ^^^^

The IR player plugin I have in Logic has the ability to route serially as well as parallelly, and comes with a handful of 'typical' impedance curve IR files. It definitely helps with the feel/sound. How to capture it separately from the speaker's frequency is the tough bit. A series resistor in the speaker line and measuring response at the connection between the resistor and the speaker should allow for measuring the curve, but will likely not be highly accurate.
 

200man

Experienced
The problems with that are fourfold, at least:

1. Not all of the cabs each have a curve in the list.

2. Additionally, any 3rd party cabs can't be predicted by FAS, so their impedance curves are not going to be available in the Axe.

3. The cab block would have to trace backwards from its input to detect which amp block it is downstream from in order to even know which amp block's impedance curve to switch, as the impedance curve is stored in and used by the amp block, to determine how the amp responds to its load.

4. The cab block can hold multiple IRs in parallel. The curves for the combination are not likely to be in the list. See #1 and do some statistics/probability math to find how many different combination curves would need to be available, given the huge number of even just factory cabs that could be loaded in each slot. That's a LOT of curves. Calculating a curve and applying it might be possible if all the cabs had curves, but, as mentioned in #1, they don't.

I think the best we can hope for is to choose an impedance curve for a similar cab and use that.
Yes I understand that...but if an IR does have the associated response data for a power amp, then the preview function in axe-edit could let you:
1-select the corresponding amp block in the preset
2-transfer the info so you wouldn’t need to flip the screens each time you hit another cab type
 

shatteredsquare

Power User
The cab block loads an IR, that's just frequency filtering, its not connected to the amp block.

The new speaker selection in the amp is related to the power amp, how different cab/speaker configurations make a power amp respond, it's dynamic, with a little bit of frequency response influence.

The ideal combination is using an IR of the same type as the speaker selection, then you have power amp resonances matching up with the IR frequency response as it was shot...but you can use the same IR you were using before, and still change the speaker type to a 1x12 or a vox 2x12 if you want, and all that will happen is you will hear the power amp start putting out a little different low end resonance, get more focused...it's just a power amp preset to simulate having different cabinet types plugged into the amp. Your favorite IRs will still sound like your favorite IRs no matter what speaker preset you use, it's just now if you use the speaker preset for the same cab type as the IR, the resonances will match up like real world and sound a m a a a a a a z i n g
 
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