Speaker Impedance Curve: Why is this in the Amp Block instead of the Cab block?

RDeraz said:
If you really want to get crazy, why not just select resistive load and create your own IC. It's fully adjustable to whatever your heart desires.:)
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bin there done that with my real cab - easy peasy except for what numbers to enter after a blurry result "rattle test" - I could go out and buy the measurement equipment to maaaybe (if I manage to do it right) get the right values. Would be a lot better if real cab makers (Mesa in my case) would publish the full data which, yes, will vary somewhat from cab to cab of same model, but I think i'd at least have a better chance at getting it right if the cab maker measures for it and provides it (the big speaker makers publish it but I'm not sure what good that is with the speakers loaded into a specific cab). For IRs a "data publishing" standard at least, is more essential since I don't have the physical cab in front of me to futz with. As stated above, these things start small / I've noticed just over the past year a lot more references to Cab IC curves in guitar related gear vids/articles etc - maybe due to Fractal's progress - dunno - but hopefully prompting Cab sellers (real and IR) to start trying to measure + publish such data so that we can at least type the numbers in - if we can get that far then the data automation can follow suit.
 
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Just thinking out loud here… but if the speaker Impedance Curve were moved to the Cab Block, what would those who don’t use the Cab Block (traditional guitar cabinet) do?
 
Dave Merrill said:
On some ideal world, each cab's impedance curve would be embedded in the IR itself, so it could be detected by any modeler. However, that ship has more or less sailed.
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not sure why that would be a conclusion - ie progress in standards/methods of data interchange between organizations has totally reshaped commerce (e-commerce) in recent decades.
 
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It totally makes sense for me having SICs in the amp block, both from a usability and authenticity point of view.

You are all giving too much importance to IRs imho, they're not replicas of a real cab and don't contain any info about intrinsic properties of a real cab either.
An IR basically is just the frequency response of a particular cab with X mic placed at Y relative position, but theoritecally you could obtain the same exact frequency response with various combinations of totally different cabs and mics, or "sinthetically" by using a very complex EQ.
Certainly something not easy to do but possible in theory.

So once you see IRs this way you'll realize that the only real property of a cab which can be simulated realistically by the axe fx (or modelers in general) is the SIC, at least at this time, all other properties (unmic'd frequency response, dispersion pattern, authentic breakup and thermal compression, etc.) will probably remain outside the control of modelers for a long time, and some of them maybe forever
 
ruso said:
Just thinking out loud here… but if the speaker Impedance Curve were moved to the Cab Block, what would those who don’t use the Cab Block (traditional guitar cabinet) do?
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I run the "totally flat" Cab IR with my SS Amp + Real Cab - totally transparent but adding the ability to low/hi cut my real cab (+ IC if it was there), and allows switching over from FR to real cab without having to turn off cab modelling or footswitching off the cab block (just switch cab block channel).
 
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Feflicker said:
Yep. This was already mentiomed but for some reason people keep debating 😅
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like I mention above - the real current challenge is not so much "where the values are captured" - it's "what the exact values are" - worth some interesting discussion I think - as far as debate about "where" : I don't care where they put the setting - we have the ability to set it - which is cools stuff!
 
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ruso said:
Just thinking out loud here… but if the speaker Impedance Curve were moved to the Cab Block, what would those who don’t use the Cab Block (traditional guitar cabinet) do?
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This wouldn’t affect those people at all since they don’t have a cab block and thus aren’t making IR selections to affect the IC in the amp block. There are various ways that could be handled, including having them continue to work just as they do now. As “what about”s go, that a pretty minor one.

That said, this is a big change and I wouldn’t expect to see it in a firmware update. It would be a future AxeFX.
 
Fractal would need to implement the inclusion of SIC data into the cab files. They already use a proprietary format for their cabs, so it would seem doable. The problem comes when importing 3rd party IRs or capturing your own IRs. How would you obtain and add the new SIC data? Measuring the impedance curve of the cab is a different process that requires dedicated hardware and software. Cab IR's on the other hand can be captured right on the Axe FX using any power amp and mic/preamp setup.

I suppose they could maybe add a feature that lets you embed one of the available factory SI curves into a given cab for future use. Even better if they add user SIC slots as an option as well.
 
mr_fender said:
Fractal would need to implement the inclusion of SIC data into the cab files. They already use a proprietary format for their cabs, so it would seem doable. The problem comes when importing 3rd party IRs or capturing your own IRs. How would you obtain and add the new SIC data? Measuring the impedance curve of the cab is a different process that requires dedicated hardware and software. Cab IR's on the other hand can be captured right on the Axe FX using any power amp and mic/preamp setup.

I suppose they could maybe add a feature that lets you embed one of the available factory SI curves into a given cab for future use. Even better if they add user SIC slots as an option as well.
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Make them “Fractal-Approved/Verified SIC IR’s”. What a great next step in the evolution of this ecosystem.
 
mr_fender said:
Measuring the impedance curve of the cab is a different process that requires dedicated hardware and software. Cab IR's on the other hand can be captured right on the Axe FX using any power amp and mic/preamp setup.

I suppose they could maybe add a feature that lets you embed one of the available factory SI curves into a given cab for future use. Even better if they add user SIC slots as an option as well.
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I don't think the IC needs to be somehow sonically embedded in an IR - just the simple numerical curve values in the IR's header / footer (whatever) that the amp block can read - just a way for IR makers to transfer the IC values in some automated way - the actual IRs stay the same as they always did. As you say: it's the measurement that's missing as it's not something most end users will/can do - the functionality is already there, + 60 samples. The simple IC values data has to be able to flow into Fractalland from outside - Fractal doesn't know about (or care about) the bajillion IC curves that go along with the bajillion IRs out there.
 
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My take on why the Impedance Curve [IC] is in the Amp block -- that is where the IC/Output Transformer calculations need to be done.

The IC is specific to a specific Speaker, a specific Cabinet Design, and a specific Output Transformer. If any 1 of those 3 factors change -- then so does the IC.

It might make sense to provide a very accurate IC for a certain artist's signature sound -- where all three factors are known. But, as soon as extra cabs are used, the impedance curve changes -- not to mention different cabinet designs, wiring, speakers or OT's. Still, signature Impedance Curves for coveted legendary Amp/Speaker combinations might make sense -- for some projects.

For me, the virtual/digital freedom of separating the Impedance Curves from the amp/speaker/cab/IR is a fantastically great, advantage. It opens up a door to a multitude of great subtle differences in sounds that can't easily be created, or managed, in the physical/analog world -- if at all.
And yet, they are very normal, very earthly sounds. It is more like someone broke the welds on the power amp's Drive and Tone Controls.

The IC is a very useful way to shape and perfect a sound.
 
sprint said:
I don't think the IC needs to be somehow sonically embedded in an IR - just the simple curve values in the IR's header / footer (whatever) that the amp block can read - just a way for IR makers to transfer the IC values in some automated way - the actual IRs stay the same as they always did. As you say: it's the measurement that's missing as it's not something most end users will/can do - the functionality is already there, + 60 samples. The data has to be able to flow into Fractalland from outside - Fractal doesn't know about (or care about) the bajillion IC curves that go along with the bajillion IRs out there.
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One thing that helps simplify this: there are far fewer IC’s than IR’s. In many cases, an entire IR package that is sold by an IR vendor, with many IRs, will share a single IC.
 
GlennO said:
One thing that helps simplify this: there are far fewer IC’s than IR’s. In many cases, an entire IR package that is sold by an IR vendor, with many IRs, will share a single IC.
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indeed! I mean, even if I had to type in the 10 or so IC info values manually into my presets, if I had some source of information that would show me the IC curve for any commercially distributed/manufactured IR or real cab I own - I think it would be a significant improvement in terms of ability to replicate through modelling, what a specific target amp / cab design is doing - Axefx already does it all - we're just short of detail specs for the modelled target designs.

Edit: The speaker section tends to excite me a lot more than the advanced tab because I can hear/feel dramatic differences when selecting different IC curves (as compared to hardly any or none when changing tube typle) so it leads me to think the speaker tab is a very significant piece. Also, with my SS Amp + Real Cabs - they came alive when I started using the "correct" (or at least what I think are correct) ICs.
 
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k - noodling with this topic during my nightly run/walk. Here's an idea expanding on Singlecutguy's thought above re: Fractal Approved/Verified IRs:

Cliff assigns a couple of his crackerjack engineers to shoot some IRs for a new Fractal Cab Pack: "FAS PROLINK1". But in addition, they will also measure with precision, the ICs of the Cabs used for the captures. Those ICs are added to the list of ICs selectable on the amp block's speaker page and named identifiably in relation to the IRs in PROLINK1 that match those ICs perfectly (as GlennO mentions above - not necessarily 1:1).

Theoretically - should those PROLINK1 IRs, when used with corresponding PROLINK1 IC selection, not sound more accurate to the amp/cab modelled?, if not better than with an approximated IC that would normally be used up to now with any IR? If yes, users benefit with more optimal amp/cab modelling via PROLINK1 purchase (maybe that means they'll also sound more pleasing more often - dunno), and, Fractal benefits from Axefx having special selectable ICs providing a more precisely modelled amp/cab experience when matched to specific corresponding cab pack IRs (not to mention no additional Axefx fw dev + the big $ from Cab Pack sales!).

Eh! Eh! Eh!
 
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From an electrical signal flow point of view the speaker impedance curve lives in the amp block. From a user point of view it lives in the cab block, because the speaker impedance curve changes depending on the cab selected. Today the "cab" means the IR, which of course also includes the mic, mic position, etc.

My vote goes towards the user point of view, putting it in the cab block along with some functionality to tie it in with the IRs. A single selection of an IR would cause the appropriate speaker impedance curve to be selected. That would be ideal for me.
 
The IC is in the amp at the right place, and is offered for the vast majority of speakers. IMO
The IC represents the electrical component of a loudspeaker.
The IR is the acoustic component of a loudspeaker.

It is nonsense to bind an IC to an IR only because the same loudspeaker is imaged in another room with 3 instead of 2 microphones. IMO

IR exists many times over even though the IC does not change.

That for support in the CAB block the info is to be seen which for an IC in the amp active is Ok. IMO

An automatic selection IR>IC makes little sense in my opinion.
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I am not at all sure if and how 2 different IC in combination would affect the frequencies, the frequency range?
 
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mr_fender said:
Fractal would need to implement the inclusion of SIC data into the cab files. They already use a proprietary format for their cabs, so it would seem doable. The problem comes when importing 3rd party IRs or capturing your own IRs. How would you obtain and add the new SIC data? Measuring the impedance curve of the cab is a different process that requires dedicated hardware and software. Cab IR's on the other hand can be captured right on the Axe FX using any power amp and mic/preamp setup.

I suppose they could maybe add a feature that lets you embed one of the available factory SI curves into a given cab for future use. Even better if they add user SIC slots as an option as well.
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I see doing this better more as a next gen feature.

IMO the current top tier for cab simulation is plugins like ML Sound Lab MIKKO that let you move multiple microphones around a virtual speaker. The way it works is that it blends together a large matrix of IRs as you move the mic around. You can blend different mics, different cabs etc without dealing with stupid file browsers. Quad Cortex has a simplified version of this (one mic per speaker, two speakers or mics in a cab block) and it greatly simplifies getting your preferred sound out of a specific cab and takes out the trial and error.

If Fractal implements something similar for its stock cabs in the next gen Axe-Fx, having the amp model impedance curve follow the cab block speaker selection becomes a more feasible feature as each cab is no longer "this big list of different mics/positions" but "this cab/speakers". Of course this becomes trickier when dealing with non-cab sim situations so having the impedance curve selection in the amp block is still the right place, but for cab sims at least it could be automated to select the appropriate curve.
 
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