Impedance Curves are my new Go-To for Tone Shaping

[JRod4928]

Of course you need a good IR to get you in the ballpark.

But the amount of shaping you can do with the impedance curve in the Amp Speaker page is astounding. Also Negative Feedback, which basically just throttles back the impedance curve....

I was dialing in a Morgan AC20 style tone and wanted more dynamic low end response, especially on mid frequency notes, like a 12th fret D. I wanted it to pop like Fender Deluxes do, for instance. It was already close, but I wanted a little more low end and adding bass EQ was making it muddy.

So I dove into impedance curves. I was using the 1x12 AC20 curve but ended up in the 1x12 Deluxe Reverb, Brit G12H75, or possibly the 1x12 Alnico Blue (strongest bass response, but gets muddy, oddly similar to how my real Alnico creams were).

The great part is that I play though amp/cab, and send FOH my IR. So since the impedance is in amp block, this affects both my amp/cab and FOH signals at the same time. I dialed in the tone through amp/cab, and it translated very very well to headphones.

Plus obviously the Impedance Curve can be tweaked in the speaker page as well. So if something isn't exactly what you want, fix it there.

I'm sure many already do this. But it was an epiphany for me.

 

[arw]

Welcome to the future!

IR and impedance/reactance is absolutely the key to tone.

 

[JRod4928]

Welcome to the future!

IR and impedance/reactance is absolutely the key to tone.

Exactly. In real world, people reach for the amps bass knob if they want more, but that affects how the amp breaks up. Or they change speakers or amps or add an EQ pedal or something.

In modeling, people buy or test hundreds of IRs and agonize over them for days, while ignoring the impedance which is a huge piece of the puzzle.

With how customizable it is, it's interesting how it isn't discussed more. No market for selling impedance curves like IRs I guess.

 

[State of Epicicity]

I do wish there were even more impedance curves, with a more detailed description of them, just for reference. But I have found you are far better off dialing in your own, regardless. It’s truly an amazing feature, because, for the first time, you fit a curve to your actual guitar playing. What a musically intuitive idea. I definitely feel the amps to be more alive when I tweak the hell out of that setting. What really inspired me was this post:

there's a time element involved too, with the speaker compression parameter high enough and master volume compressing, the speaker time constant parameter can tune how fast or slow the low end resonance flexes and returns. Once you have speaker LF resonance centered in a good sounding spot you can tune speaker time while chugging until it lines up right with master volume compression, so they both flex and return at the same rate. With Recto 2 master at ~1.3 and LF resonance at ~85Hz for me it was like ~700ms of speaker time constant where everything started dancing together. bring bias excursion time up to ~6ms too and see if it doesn't purr like crazy

then this:

if the 'sound' of high volume is the 'sound' of physical material starting to come tf apart in all glorious equipment abuse, the most potent knob for that is Xformer drive and speaker drive. if you like the way it sounds but still want to actually 'play' the sound, with Xformer drive causing a meltdown up past 4, you can move the distortion out of the way and put it right where you want it with the speaker page LF resonance freq, if you move it down towards 70 Hz you can make room for some guitar to come through with it still being floppy in the sub bass. you can tune the top end too with speaker high freq, if you bring it down towards ~900 Hz the guitar will still cut through a floppy output transformer. Speaker drive just makes a mess but it's fun af

 

[sprint]

In modeling, people buy or test hundreds of IRs and agonize over them for days, while ignoring the impedance which is a huge piece of the puzzle.

With how customizable it is, it's interesting how it isn't discussed more. No market for selling impedance curves like IRs I guess.

IC may be an important piece of the puzzle but it's not designed for general tone shaping afaik - an IC is a specific attribute of a specific cab causing amp modelling to react correctly to that specific cab ir or real cab which, in turn, should result in an improvment in "reactivity" and tone. So there really is only one "correct" IC value for a given amp / cab pair. What seems to be happening maybe, is that folks (me for sure) are having trouble determining the correct values for, or hearing, or feeling this reactive handshake, so they abandon finding that specific value and just use the IC for general tone shaping which imo kind of defeats the purpose and maybe even throws a wrench into the way the amp modelling is intended to behave. Nothing wrong with tweaking anything to what sounds good for a specific tone (not trying to rain on anyone's parade), but I tend to think my love of Axfx is coming as much from it's accuracy of modelling correct real tube amp internals as it is from the number of different ways to spin dials by ear. I really wish there was a better method for confirming "correct" IC value - maybe mixermang is onto it in the posts referenced above - dunno.

I feel the same about tube based power amps - been gassing to trade my Matrix GT1000fx for a Synergy 5050 or LxII, or Power Station, but, given all the precision of effort Fractal puts into modelling tube circuts accurately it seems defeating to throw a bunch of real tubes onto the end of the already modelled tube circut chain to make it sound better to my ear for some specific tone - would rather keep pushing the envelope on the tube amp modelling accuracy to overcome any remaining gaps compared to real tube circuts and arrive at models that react like the real thing in all tonal scenarios with tweaking contained to only the authenic page and no nead to delve into trying to tone shape with the advanced parameters which, though it may produce a great specific tone, I'm not sure will produce a range of best authentic tones via authentic page for a given amp/cab.

 

[JRod4928]

IC may be an important piece of the puzzle but it's not designed for general tone shaping afaik - an IC is a specific attribute of a specific cab causing amp modelling to react correctly to that specific cab ir or real cab which, in turn, should result in an improvment in "reactivity" and tone. So there really is only one "correct" IC value for a given amp / cab pair. What seems to be happening maybe, is that folks (me for sure) are having trouble determining the correct values for, or hearing, or feeling this reactive handshake, so they abandon finding that specific value and just use the IC for general tone shaping which imo kind of defeats the purpose and maybe even throws a wrench into the way the amp modelling is intended to behave. Nothing wrong with tweaking anything to what sounds good for a specific tone (not trying to rain on anyone's parade), but I tend to think my love of Axfx is coming as much from it's accuracy of modelling correct real tube amp internals as it is from the number of different ways to spin dials by ear. I really wish there was a better method for confirming "correct" IC value - maybe mixermang is onto it in the posts referenced above - dunno.

I feel the same about tube based power amps - been gassing to trade my Matrix GT1000fx for a Synergy 5050 or LxII, or Power Station, but, given all the precision of effort Fractal puts into modelling tube circuts accurately it seems defeating to throw a bunch of real tubes onto the end of the already modelled tube circut chain to make it sound better to my ear for some specific tone - would rather keep pushing the envelope on the tube amp modelling accuracy to overcome any remaining gaps compared to real tube circuts and arrive at models that react like the real thing in all tonal scenarios with tweaking contained to only the authenic page and no nead to delve into trying to tone shape with the advanced parameters which, though it may produce a great specific tone, I'm not sure will produce a range of best authentic tones via authentic page for a given amp/cab.

My whole point is that an IC should be considered as a tool much like IRs or Drive blocks etc. In reality, changing an IC is the same as changing a real speaker or cab. But most people treat ICs as an advanced parameter that shall not be touched.

As far as I'm concerned, tweaking parameters of a chosen IC is just changing to some idealized version of that cab that we prefer. Or perhaps it is changing closer to some other speaker that we are trying to emulate, but isn't an option in the current AXE. I don't think this takes away from authenticity. People change speakers in real cabs all the time, and achieve a new sound that they like possibly because of the IC of that specific speaker, but they just don't realize it.

As for Tone shaping and response. I partially agree. Guitar Tone is more than just EQ. It is response and feel.... I until yesterday I was GASing for a Power Station also - because I wanted that tube Pop sound that I referred to in OP. I found it by selecting a new IC... and turning up the volume. In my eyes all I did was virtually connected the Morgan AC20 to a different cab, still authentic... and even if it wasn't, I don't care because I like it.

 

[JRod4928]

I do wish there were even more impedance curves, with a more detailed description of them, just for reference. But I have found you are far better off dialing in your own, regardless. It’s truly an amazing feature, because, for the first time, you fit a curve to your actual guitar playing. What a musically intuitive idea. I definitely feel the amps to be more alive when I tweak the hell out of that setting. What really inspired me was this post:



then this:

The posts you quoted reveal that I have a lot to learn lol.

But you're right, this is about feel and you can dial this to your playing. I'm not yet to the point where I'm finding the resonant frequency of my cab and tuning an IC to it. But maybe if I have time someday. I think @2112 did this in a video, unless I'm misremembering.

 

[sprint]

My whole point is that an IC should be considered as a tool much like IRs or Drive blocks etc. In reality, changing an IC is the same as changing a real speaker or cab. But most people treat ICs as an advanced parameter that shall not be touched.

As far as I'm concerned, tweaking parameters of a chosen IC is just changing to some idealized version of that cab that we prefer. Or perhaps it is changing closer to some other speaker that we are trying to emulate, but isn't an option in the current AXE. I don't think this takes away from authenticity. People change speakers in real cabs all the time, and achieve a new sound that they like possibly because of the IC of that specific speaker, but they just don't realize it.

As for Tone shaping and response. I partially agree. Guitar Tone is more than just EQ. It is response and feel.... I until yesterday I was GASing for a Power Station also - because I wanted that tube Pop sound that I referred to in OP. I found it by selecting a new IC... and turning up the volume. In my eyes all I did was virtually connected the Morgan AC20 to a different cab, still authentic... and even if it wasn't, I don't care because I like it.

I do appreciate, and get your point, and would say if tweaking ICs (or any advanced parms) gets you a tone u like, then have at'r - it can't hurt and can lead to interesting discoveries of all sorts. I'm just saying that afaik irl there is only one correct IC value set to any given amp/cab pair and that single value set should offer some magic within the modelling as it does irl - and afaik Axfx Amp modelling is set up to react to IC in a specific and authentic as possible way (at least until next fw when it improves lol), so, if one chooses an IC in a tone shaping context that sounds good by ear, but is far away from the one correct value for that amp/cab pair, then what does that mean for the amp modelling's ability to do it's thing authentically, correctly, and well? - (one of the main things that initially attracts many to Axefx).

I also wonder sometimes, when I see comments about arriving at great tones by tweaking more "internal amp circut" modelled values, if that also means:

• the resulting tone is great at varying gain or input levels.
• the modelled amp circut maintains it's expected character and still operates desireably under varying conditions (varying tone stack settings, varying mv settings, various pedals applied ... etc).

 

[JRod4928]

I do appreciate, and get your point, and would say if tweaking ICs (or any advanced parms) gets you a tone u like, then have at'r - it can't hurt and can lead to interesting discoveries of all sorts. I'm just saying that afaik irl there is only one correct IC value set to any given amp/cab pair and that single value set should offer some magic within the modelling as it does irl - and afaik Axfx Amp modelling is set up to react to IC in a specific and authentic as possible way (at least until next fw when it improves lol), so, if one chooses an IC in a tone shaping context that sounds good by ear, but is far away from the one correct value for that amp/cab pair, then what does that mean for the amp modelling's ability to do it's thing authentically, correctly, and well? - (one of the main things that initially attracts many to Axefx).

I also wonder sometimes, when I see comments about arriving at great tones by tweaking more "internal amp circut" modelled values, if that also means:

• the resulting tone is great at varying gain or input levels.
• the modelled amp circut maintains it's expected character and still operates desireably under varying conditions (varying tone stack settings, varying mv settings, various pedals applied ... etc).

Understood. No worries man

I dont mess with advanced parameters a lot for the reasons you stated - I want a close to real as possible because how will I know if the AC20 in playing is still like an AC20 if I've tweaked it so far that now it sounds and feels like a plexi lol?

However, in my eyes changing IC is a virtual speaker change that impacts how the Power Amp responds, which would happen in real life as well - so amp accuracy is maintained. The Axe fx models are not profiles like a Kemper. So regardless of the speaker it was connected to when Cliff was modeling it, the amp model itself is still accurate and should respond to speaker changes (whether real or virtual) accurately.

Either way though, IC is extremely powerful and people should use it

 

[State of Epicicity]

The posts you quoted reveal that I have a lot to learn lol.

No, believe me, I’m the one with a lot to learn. To me, the Fractal products are made for anyone from musicians to electrical engineers. I’m just a musician. I’ve never modded a real amp or built a kit amp or anything like that, and I cannot wrap my mind around many of the explanations I read about amps’ functions. But what those couple of posts taught me were there are parameters that completely bring amps to life.

Just one small example is Speaker Compression. This is just my feeling, but I find I can make an amp model come alive in headphones with just that parameter. The rest is just “turn this knob and see if it sounds better or worse.” And it’s great to have access to the accuracy of models, but so many great guitarists get their’s modded or built to spec, or use unintuitive combinations, that I think the advanced parameters are truly the way to find your spirit’s guitar tone, just whatever it is that sonically makes you you.

 

[316ms]

Is it possible to see a screen shot of a preferred IC for a bogner 2x12 cab w/vinatge 30s? I have just began this tweaking expedition and it's endless. The amps I am using with a matrix pA are mainly Dizy VH4, Mesa, 5150,Plexi., not sure if that matters but just in case. Thanks in advance

 

[laxu]

IC may be an important piece of the puzzle but it's not designed for general tone shaping afaik - an IC is a specific attribute of a specific cab causing amp modelling to react correctly to that specific cab ir or real cab which, in turn, should result in an improvment in "reactivity" and tone. So there really is only one "correct" IC value for a given amp / cab pair. What seems to be happening maybe, is that folks (me for sure) are having trouble determining the correct values for, or hearing, or feeling this reactive handshake, so they abandon finding that specific value and just use the IC for general tone shaping which imo kind of defeats the purpose and maybe even throws a wrench into the way the amp modelling is intended to behave. Nothing wrong with tweaking anything to what sounds good for a specific tone (not trying to rain on anyone's parade), but I tend to think my love of Axfx is coming as much from it's accuracy of modelling correct real tube amp internals as it is from the number of different ways to spin dials by ear. I really wish there was a better method for confirming "correct" IC value - maybe mixermang is onto it in the posts referenced above - dunno.

I feel the same about tube based power amps - been gassing to trade my Matrix GT1000fx for a Synergy 5050 or LxII, or Power Station, but, given all the precision of effort Fractal puts into modelling tube circuts accurately it seems defeating to throw a bunch of real tubes onto the end of the already modelled tube circut chain to make it sound better to my ear for some specific tone - would rather keep pushing the envelope on the tube amp modelling accuracy to overcome any remaining gaps compared to real tube circuts and arrive at models that react like the real thing in all tonal scenarios with tweaking contained to only the authenic page and no nead to delve into trying to tone shape with the advanced parameters which, though it may produce a great specific tone, I'm not sure will produce a range of best authentic tones via authentic page for a given amp/cab.

I totally agree with this.

I just spend a bit of time trying my Axe-Fx 3 into two real poweramps and cabs. The setup using two amp models:

1. Left: Plexi 100 Jumped -> BluGuitar Amp 1 Mercury Edition fx return -> Bluetone 4x10 cab closed back w/ 10" Greenbacks.
2. Right: Matchless DC30 or Class A 30 TB -> Fryette Power Station 100 line in -> Tube Town 1x12 convertible back w/ Celestion Alnico Gold, using closed back this time.

I have a Victory VC35 normally hooked up to the Fryette and 1x12. It's a great Vox-meets-Matchless type 35W lunchbox head.

So the premise here was "can I make my Axe-Fx 3 models sound and feel the same as the BluGuitar and Victory amps". I matched them all with a decibel meter to a "still home friendly but a bit loud" volume of about 85-90 dB @ 1m so results may vary at real stage volumes.

Initial results for the Plexi vs BluGuitar were a bit disappointing. The Fractal model sounded pretty harsh. I knew it sounded fine when I had built the preset originally using cab sims so I decided to see if I could do something about it. Changing the speaker impedance curve to 4x10 JTM45 fixed it and this seems to be pretty close to how the BluGuitar reacts with my 4x10 cab. The BluGuitar "Vintage" channel sounded and felt nearly identical to the Fractal model. So that side was a success.

Moving on to the Matchless and Vox models, this one was much harder. The Victory -> Fryette always had just the right kind of sparkle to its highs where they are enjoyable but not grating or fizzy and similarly the lows were full but not tubby. I had a hard time finding an equivalent 1x12 impedance curve that would work here as there's not one directly for Alnico Gold. It doesn't help that the list of impedance curves is not sorted by name!

After trying a bunch of 1x12 or 2x12s and not quite getting there, I decided to see what the resistive load setting could do. The Fryette presence/depth controls were not helpful and the sound was mostly just dull and felt uninspiring. So I went to the speaker tab and started messing with the low/high impedance settings in a "I don't really know what I'm doing" manner. Now I started getting somewhere and after I had built a nice LF mound and skislope up to HF mountain it started to sound and feel closer to what I was getting from the Victory but I was still not getting as good results. Decided to leave it for now and need to give this another go with fresh ears.

Which brings me here with the conclusion that getting that speaker impedance section right is surprisingly important. I generally have no complaints about the defaults when playing through cab sims and studio monitors but with real poweramps and cabs it's much more relevant to adjust them right.

Obviously just using the real amps here is the shortcut to being happy about tone and feel but the Axe-Fx 3 does greatly simplify running a stereo amp setup as things like fx levels and setting volumes becomes a lot more straightforward.

 

[State of Epicicity]

@laxu I think the speaker impedance curves are the most important overlooked parameter in the unit. To me, you may as well be talking about changing amps or changing IRs when you talk about altering impedance curves. I think just more tweaking will get you where you want to go. I suggest looping yourself playing to get there. But the hard part really is the high end, as I see it. I just heavily modded the Deluxe Verb last night and just totally made my own impedance curve, and it was no less than revelatory for that particular tone. I was able to get the low end to purr in this gnarly yet very pleasing way, like the way people talk about a Neve strip or something. It was awesome. Dialing in the high end on the impedance curve was not as daunting to me as it usually is, and I found that, for parameters where I'm pretty unsure, I tend to use Axe-Edit to move the knobs, as opposed to my M.O. of usually using the front panel of the unit itself; I do this so I can actually use the Undo feature in Axe-Edit, so I don't get an advanced parameter negatively affecting the character of the amp and can't figure out what the default pleasing sounding setting was.

 

[JRod4928]

After trying a bunch of 1x12 or 2x12s and not quite getting there, I decided to see what the resistive load setting could do. The Fryette presence/depth controls were not helpful and the sound was mostly just dull and felt uninspiring. So I went to the speaker tab and started messing with the low/high impedance settings in a "I don't really know what I'm doing" manner. Now I started getting somewhere and after I had built a nice LF mound and skislope up to HF mountain it started to sound and feel closer to what I was getting from the Victory but I was still not getting as good results. Decided to leave it for now and need to give this another go with fresh ears.

Which brings me here with the conclusion that getting that speaker impedance section right is surprisingly important. I generally have no complaints about the defaults when playing through cab sims and studio monitors but with real poweramps and cabs it's much more relevant to adjust them right.

Obviously just using the real amps here is the shortcut to being happy about tone and feel but the Axe-Fx 3 does greatly simplify running a stereo amp setup as things like fx levels and setting volumes becomes a lot more straightforward.

I'm curious if your LF mound happens to coincide with the natural resonant frequency of whatever your 1x12 or 2x12 is.... and (we'll never know this) if the FAS measured impedance curve would match up with your custom IC.

I found an astoundingly interesting and relevant video on this topic on Youtube that discussed how the physical location of the speaker coil within the magnet's magnetic field affects the impedance - and explains why the impedance is variable with respect to frequency.... so as cab size, configuration, open/closed back, etc changes, it impacts the air pressure inside the cab, which affects the location of the coil within the magnetic field, etc etc.... so this is why the SIZE, Open/Closed, # speakers, etc all affects the impedance curve. Wonder if the custom curve you're dialing in is just optimized for that specific cab, because of the variables I'm discussing. Whereas some other 1x12 or 2x12 IC in the FAS unit is not optimized and doesn't work for your specific cab.

Side note - I'm playing a 1x12 Mesa Cab, so maybe this is why I'm finding good results also because I have always just used the default IC, but may not be ideal for my Mesa. And while the 1x12 IC options in the AXE are better than say a 4x12 Marshall, it still could use some tweaking to get exactly right.

 

[laxu]

I'm curious if your LF mound happens to coincide with the natural resonant frequency of whatever your 1x12 or 2x12 is.... and (we'll never know this) if the FAS measured impedance curve would match up with your custom IC.

I found an astoundingly interesting and relevant video on this topic on Youtube that discussed how the physical location of the speaker coil within the magnet's magnetic field affects the impedance - and explains why the impedance is variable with respect to frequency.... so as cab size, configuration, open/closed back, etc changes, it impacts the air pressure inside the cab, which affects the location of the coil within the magnetic field, etc etc.... so this is why the SIZE, Open/Closed, # speakers, etc all affects the impedance curve. Wonder if the custom curve you're dialing in is just optimized for that specific cab, because of the variables I'm discussing. Whereas some other 1x12 or 2x12 IC in the FAS unit is not optimized and doesn't work for your specific cab.

Side note - I'm playing a 1x12 Mesa Cab, so maybe this is why I'm finding good results also because I have always just used the default IC, but may not be ideal for my Mesa. And while the 1x12 IC options in the AXE are better than say a 4x12 Marshall, it still could use some tweaking to get exactly right.

I have absolutely no idea, this was entirely just turning knobs and playing and listening and comparing. It's sheer luck that the 4x10 JTM45 curve happens to match quite closely to my 4x10 cab which is as niche as it gets in the first place.

 

[sprint]

I totally agree with this.

I just spend a bit of time trying my Axe-Fx 3 into two real poweramps and cabs. The setup using two amp models:

1. Left: Plexi 100 Jumped -> BluGuitar Amp 1 Mercury Edition fx return -> Bluetone 4x10 cab closed back w/ 10" Greenbacks.
2. Right: Matchless DC30 or Class A 30 TB -> Fryette Power Station 100 line in -> Tube Town 1x12 convertible back w/ Celestion Alnico Gold, using closed back this time.

I have a Victory VC35 normally hooked up to the Fryette and 1x12. It's a great Vox-meets-Matchless type 35W lunchbox head.

So the premise here was "can I make my Axe-Fx 3 models sound and feel the same as the BluGuitar and Victory amps". I matched them all with a decibel meter to a "still home friendly but a bit loud" volume of about 85-90 dB @ 1m so results may vary at real stage volumes.

Initial results for the Plexi vs BluGuitar were a bit disappointing. The Fractal model sounded pretty harsh. I knew it sounded fine when I had built the preset originally using cab sims so I decided to see if I could do something about it. Changing the speaker impedance curve to 4x10 JTM45 fixed it and this seems to be pretty close to how the BluGuitar reacts with my 4x10 cab. The BluGuitar "Vintage" channel sounded and felt nearly identical to the Fractal model. So that side was a success.

Moving on to the Matchless and Vox models, this one was much harder. The Victory -> Fryette always had just the right kind of sparkle to its highs where they are enjoyable but not grating or fizzy and similarly the lows were full but not tubby. I had a hard time finding an equivalent 1x12 impedance curve that would work here as there's not one directly for Alnico Gold. It doesn't help that the list of impedance curves is not sorted by name!

After trying a bunch of 1x12 or 2x12s and not quite getting there, I decided to see what the resistive load setting could do. The Fryette presence/depth controls were not helpful and the sound was mostly just dull and felt uninspiring. So I went to the speaker tab and started messing with the low/high impedance settings in a "I don't really know what I'm doing" manner. Now I started getting somewhere and after I had built a nice LF mound and skislope up to HF mountain it started to sound and feel closer to what I was getting from the Victory but I was still not getting as good results. Decided to leave it for now and need to give this another go with fresh ears.

Which brings me here with the conclusion that getting that speaker impedance section right is surprisingly important. I generally have no complaints about the defaults when playing through cab sims and studio monitors but with real poweramps and cabs it's much more relevant to adjust them right.

Obviously just using the real amps here is the shortcut to being happy about tone and feel but the Axe-Fx 3 does greatly simplify running a stereo amp setup as things like fx levels and setting volumes becomes a lot more straightforward.

Interesting - Going at it logically as I could with what I think I know so far I would have:

• for the SS BlueGuitar side, try to measure/determine the actual resonance of the 410 and set the IC to that.
• for the Powerstation Side I would expect the IC to be already set between it and the 112 since afaik Powerstation is a tube based power amp, so IC is set to off/RL for that side. I'd have power amp modelling on to provide the correct DC30 p.a. gain structure and color into the clean powerstation amp, but, those tubes in the powerstation would really be bugging me as they just don't make since in the big picture that I really want to make sense - sorry ear tweaker people, but I also want to tweak by eyes and brain.

 

[laxu]

Interesting - Going at it logically as I could with what I think I know so far I would have:

• for the SS BlueGuitar side, try to measure/determine the actual resonance of the 410 and set the IC to that.
• for the Powerstation Side I would expect the IC to be already set between it and the 112 since afaik Powerstation is a tube based power amp, so IC is set to off/RL for that side. I'd have power amp modelling on to provide the correct DC30 p.a. gain structure and color into the clean powerstation amp, but, those tubes in the powerstation would really be bugging me as they just don't make since in the big picture that I really want to make sense - sorry ear tweaker people, but I also want to tweak by eyes and brain.

All I can say is that using resistive load setting with the Axe-Fx does not give me the right results with the PS. To be fair the Axe-Fx doesn't directly model my amp either but I feel Vox and Matchless models should be very close. I've tried the Fryette with the 4x10 and again preferred the results from the JTM45 4x10 impedance curve.

 

[JRod4928]

Interesting - Going at it logically as I could with what I think I know so far I would have:

• for the SS BlueGuitar side, try to measure/determine the actual resonance of the 410 and set the IC to that.
• for the Powerstation Side I would expect the IC to be already set between it and the 112 since afaik Powerstation is a tube based power amp, so IC is set to off/RL for that side. I'd have power amp modelling on to provide the correct DC30 p.a. gain structure and color into the clean powerstation amp, but, those tubes in the powerstation would really be bugging me as they just don't make since in the big picture that I really want to make sense - sorry ear tweaker people, but I also want to tweak by eyes and brain.

All I can say is that using resistive load setting with the Axe-Fx does not give me the right results with the PS. To be fair the Axe-Fx doesn't directly model my amp either but I feel Vox and Matchless models should be very close. I've tried the Fryette with the 4x10 and again preferred the results from the JTM45 4x10 impedance curve.

@laxu 's experience is helping me understand what you meant, @sprint . The amp/cab 'handshake' you referred to. Unfortunately we don't have all the combinations of cabs/speakers, so sometimes we have to use a best approximation for IC, and tweak as needed. Like this 4x10 situation. Not a huge surprise that the 4x10 IC is the best IC for a 4x10.

I've been playing through a real 1x12 but with 'default' amp setting IC's. Now I understand why there's a global IC setting....

Although, it would be nice to be able to save a custom IC. Or just add a few IC's to the end of the list and name it 'Custom 1, 2 ,etc' for those of us with multiple cabs - which would obviously be selectable as a global IC as well @FractalAudio

 

[sprint]

+1 - we have the real #, or we approximate, and if we can't approximate it then it's by ear. I guess I have not given up on, or am advocating for, speaker makers and cab builders and IR builders ... to be more proactive in recognizing that IC is an important link in modelling and to help users a bit more in determining this important IC value in modellers (well Axefx mostly as Fractal's in the few who've seemed to have key'd into this piece afaik). IMO trying to list them may not even be manageable as there are countless combinations given that each speaker can have it's own curve when then get skewed based on what cab it's in. For our own cabs, the rattle test is kind of doable for LFR but the HFR and cab bumps are another thing i'd have no clue how to get those without some precision measuring instruments (even then, there is expertise involved in using those instruments). My cabs are mass produced Mesa 112s so Mesa has that spec somewhere, they just don't publish it (would be useful even if slightly varying from one cab instance to another). There's hope though - seems Vahallir is publishing LFR with their IRs - lets get others on board. Speaker IC speaks are fairly well published - I have mine for CL80 and V30 - wonder if there's a way to, given a speaker IC, to extrapolate with cab dimensions, number of speakers, open/closed back,ported / not, port location+size, ... specs to yield an in the ball park IC for a given real cab? Interesting stuff.

 

[JRod4928]

+1 - we have the real #, or we approximate, and if we can't approximate it then it's by ear. I guess I have not given up on, or am advocating for, speaker makers and cab builders and IR builders ... to be more proactive in recognizing that IC is an important link in modelling and to help users a bit more in determining this important IC value in modellers (well Axefx mostly as Fractal's in the few who've seemed to have key'd into this piece afaik). IMO trying to list them may not even be manageable as there are countless combinations given that each speaker can have it's own curve when then get skewed based on what cab it's in. For our own cabs, the rattle test is kind of doable for LFR but the HFR and cab bumps are another thing i'd have no clue how to get those without some precision measuring instruments (even then, there is expertise involved in using those instruments). My cabs are mass produced Mesa 112s so Mesa has that spec somewhere, they just don't publish it (would be useful even if slightly varying from one cab instance to another). There's hope though - seems Vahallir is publishing LFR with their IRs - lets get others on board. Speaker IC speaks are fairly well published - I have mine for CL80 and V30 - wonder if there's a way to, given a speaker IC, to extrapolate with cab dimensions, number of speakers, open/closed back,ported / not, port location+size, ... specs to yield an in the ball park IC for a given real cab? Interesting stuff.

Interesting question......... with a lot of variables.

Someone with more knowledge can shoot holes in this theory... but................

I just realized that the cab (not speaker) resonant frequency (I think) is the frequency where the air waves inside the cab reflect and hit the speaker cone at the speaker's peak amplitude when the speaker is producing its resonant frequency. Just like when you experiment with a slinky and fling it just as the wave returns to you, producing an even larger wave. The slinky (speaker) itself has its own resonant freq, and you (moving cab air) are just amplifying it....... The IC shows a larger peak impedance at this frequency because when the speaker is at this resonant frequency, the speaker cone is being pushed further by the cab's reflecting air waves, thus moving the coil further outside the magnet's magnetic field (and larger impedance?).... or maybe it's the exact opposite?

This all has little to do with plywood vs mdf vs solid wood, baffle size, wood thickness, etc. It's the resonance of the AIR inside the cab, not the cab materials. So the cab resonance and vibration isn't caused by some resonant frequency of a geometric shape like a cube (your cab), it's the resonant frequency of the air moving around inside of it...... so wood material used maybe captured by the IR, not the IC. No one talks about wood types with respect to IC's.

Just a random thought I had. Starting to understand where cab and speaker characteristics play off one another and how it all works together........ maybe, unless I'm way off base.