Speaker Impedance Curves for Axe 2

[Ripley]

With the new speaker impedance curves in the amp block introduced in fw11 for Axe 3, is there a difference in the way the firmware code is written in the Axe 3 compared to the Axe 2, so that the curves interact differently with the impulse response?
Watching the videos already posted by Leon and Burgs, I can see that there are a few extra peaks in the middle of the curve in some cases, but If I set the rest of the parameters in the Axe 2 similarly to those defaults in the Axe 3, would this give an improvement in tone/feel as reported by our lucky Axe 3 owner friends?
Of course I am hoping Cliff will give us Axe 2 owners a Christmas present via a new firmware, but failing that and assuming an improvement can be made, would somebody kindly post screenshots of the impedance curve parameters from an Axe 3 please?

 

[∞Fractals]

Don’t confuse Impulse Responses (cabinet simulation/eq) with Impedance curves (power amp:speaker transducer interaction simulation).

 

[Ripley]

Ok, let me re-phrase that, does the speaker impedance curve interact differently in the Axe 3 'system' compared to the Axe 2, because of a difference in the way the firmware is written (assuming similar curve parameters)?

 

[∞Fractals]

Ok, let me re-phrase that, does the speaker impedance curve interact differently in the Axe 3 'system' compared to the Axe 2, because of a difference in the way the firmware is written (assuming similar curve parameters)?

Is there a speaker Impedance curve in the 2 (other than generic)?

If you cannot select one, then I doubt it’s implemented.

 

[zenaxe]

If the graphs are anything to go by, they are more detailed in the III ... in the 2 they only have two main points the user can modify. Whereas in addition to the different settings in the drop down, the 3 curves have multiple sub peaks and valleys so they are clearly not the same. So it is more than just plugging in new high and low resonance values in on the 2, I think.

 

[axifist]

I asked myself the very same thing and wanted to ask this very same question.

My understanding is that the default speaker impedance curve in the amps of the AxeII are set for a cabinet typically used with it. So the curve is in fact based on real cabs, even though they are not as accurate as they are implemented right now in the III. Look e.g. at the default curve on a Plexi. Its default cab is most probably a 4x12 Marshall with Greenbacks. Comparing those default values with the 4x12 Brit Marshall (can be seen in Leon's video) in the III shows very similar values.

So my guess is that it definitely makes sense to use the values seen in Leons video. I did exactly this, because I play a 4x12 Marshall with Greenbacks, but I replaced two Greenbacks with 2 V30s, which makes things a bit more complicated. What I adjusted so far are the average values between the 4x12 Brit Greenback and the 4x12 Brit AX (also in Leon's video). Using the average value is the best I could come up with... (edit: I forgot, that maybe the Low Res Q probably should be smaller in that case) Since they are quite close to each other I feel like I'm very close to the "truth".

My AxeII+Matrix+4x12 never sounded better. Could be because of the Ares2 update or the new speaker impedance values. I guess it's a combination of both. And a bit of a placebo effect of course

edit: In that case it would be cool to have some sort of library of values somewhere on the wiki. It would of course be even more awesome if Cliff ported this new magic to the II. But if not, a simple video of scrolling through the curves would be enough, we II guys would love to export the values by hand!

 

[yyz67]

Ok, let me re-phrase that, does the speaker impedance curve interact differently in the Axe 3 'system' compared to the Axe 2, because of a difference in the way the firmware is written (assuming similar curve parameters)?

Only @FractalAudio can answer but I'm guessing the basic functionality is the same regarding impedance in the 2 and 3 as a basic part of tube amp simulation (minus other FW differences). The impedance data being used in the 3 is now both more accurate (includes more resonances based on actual measurements) and is more easily tweaked via predefined curve selection and cab res %. The 2 already has the ability to change the core resonance parameters by hand.

 

[Ripley]

I asked myself the very same thing and wanted to ask this very same question.

My understanding is that the default speaker impedance curve in the amps of the AxeII are set for a cabinet typically used with it. So the curve is in fact based on real cabs, even though they are not as accurate as they are implemented right now in the III. Look e.g. at the default curve on a Plexi. Its default cab is most probably a 4x12 Marshall with Greenbacks. Comparing those default values with the 4x12 Brit Marshall (can be seen in Leon's video) in the III shows very similar values.

So my guess is that it definitely makes sense to use the values seen in Leons video. I did exactly this, because I play a 4x12 Marshall with Greenbacks, but I replaced two Greenbacks with 2 V30s, which makes things a bit more complicated. What I adjusted so far are the average values between the 4x12 Brit Greenback and the 4x12 Brit AX (also in Leon's video). Using the average value is the best I could come up with... Since they are quite close to each other I feel like I'm very close to the "truth".

My AxeII+Matrix+4x12 never sounded better. Could be because of the Ares2 update or the new speaker impedance values. I guess it's a combination of both. And a bit of a placebo effect of course

edit: In that case it would be cool to have some sort of library of values somewhere on the wiki. It would of course be even more awesome if Cliff ported this new magic to the II. But if not, a simple video of scrolling through the curves would be enough, we II guys would love to export the values by hand!

Exactly what I was thinking, I realise there is more detail in the 3 curves, but ask myself would I get better results dialling a more suitable curve by adjusting the resonant peak frequency, amplitude and slope, based on the 3 default curves?

 

[yyz67]

would I get better results

Go for it. Cliff has said that the original curves (in the axe) were approximate and that one is always free to adjust resonances etc. So to "match" your 2 to the new resonance values of default curves in the 3 is totally valid. If it gives "better results" is up to you.

 

[zenaxe]

Exactly what I was thinking, I realise there is more detail in the 3 curves, but ask myself would I get better results dialling a more suitable curve by adjusting the resonant peak frequency, amplitude and slope, based on the 3 default curves?

I would expect so. It is certainly worth tryin.

 

[Ripley]

Go for it. Cliff has said that the original curves (in the axe) were approximate and that one is always free to adjust resonances etc. So to "match" your 2 to the new resonance values of default curves in the 3 is totally valid. If it gives "better results" is up to you.

Now all I need are the Axe 3 speaker impedance curve parameters, anyone?

 

[∞Fractals]

FWIW ... and I have not validated this (not my expertise), but I thought I recall a infamous speaker designer (JM) recently saying that you couldn't derive impedance curves from the resonance curves.

I have no idea, but FAS could shed some light here.

 

[Ripley]

FWIW ... and I have not validated this (not my expertise), but I thought I recall a infamous speaker designer (JM) recently saying that you couldn't derive impedance curves from the resonance curves.

I have no idea, but FAS could shed some light here.

Even if JM (whoever that is) is correct, it makes no difference, whatever Cliff has done in FW11 has had, in most peoples opinion, a very positive effect on the overall tone and feel of the unit.
So my last time of asking, can anyone please post some screenshots of the new default speaker impedance parameters, so that us Axe 2 owners can at least try them to see if an improvement can be made in our units?

 

[∞Fractals]

Even if JM (whoever that is) is correct, it makes no difference, whatever Cliff has done in FW11 has had, in most peoples opinion, a very positive effect on the overall tone and feel of the unit.
So my last time of asking, can anyone please post some screenshots of the new default speaker impedance parameters, so that us Axe 2 owners can at least try them to see if an improvement can be made in our units?

OK
I’ve offered all the help I’ve got.
Good luck.

 

[∞Fractals]

FYI:

Nov 19, 2019
Jay M.

Dave M said:

“Do I understand correctly that a peak in the impedance curve corresponds to or is equivalent to a peak in frequency response

A peak in the impedance of a speaker will cause a peak in the magnitude response of the amp. How large that peak will be depends heavily on the design of the amp's output stage. The lower the amp's outputimpedance, the smaller will be any peak in its response due to the impedance of the speaker it is driving.

The output impedance of the amp is affected by how much, if any, negative feedback it uses, the turns ratio of the output transformer (if present), and the source impedance of the amp's output devices. In addition to magnitude response, the interaction between the amp's output impedance and the load impedance presented by the speaker affects the amp's nonlinear (distortion) behavior.

“Handy if you can look at one and know the other.”

You can't

 

[Admin M@]

The Axe-Fx III has MANY improvements to power amp modeling that happened after development for the II was stopped. Even if you could use the older parameters to dial in something like the data shown in the new measured impedance curves, the effect would not be the same, and I think it would be up to you to decide whether or not it sounded "better".