Same Speaker Impedance Curve changes with different Amps .... is this normal ?

[ben ifin]

Hi all !

I am using the same 2x12 CL80 MBritt IR with the same settings in each preset.

To go with it I am using the same 2x12 CL80 Speaker Impedance Curve with each preset.

I have noticed that if I keep the Speaker Impedance Window in view, and scroll through my presets, the shape of the curve and the settings of the 2x12 CL80 Speaker impedance curve change for each different amp in use (?)

=> is this normal behavior / to be expected (?)

Apologies upfront if this is an obvious question, but it is outside my knowledge range

Ben

 

[chris]

Is the curve changing and the name not updating? If you click away and back to that tab did the name change?

 

[mr_fender]

Different amps have different output transformers and power amp specs, so the same speaker load will still cause a different response.

 

[sprint]

normal afaik - in Axfx3 at least, different amp models influence the amp block speaker tab curve differently via varying transformer parameters as mentioned above - specifically, the "XFormer Low Freq" and "XFormer Hi Freq" parameters on the amp block speaker tab will change as different amp models are selected, thus influencing the shape of the overall amp block speaker tab curve via those two parameters, and in addition to these other influencers on that displayed curve:

• the "Speaker Impedance Curve" (SIC) dropdown selection on the amp block speaker tab which also changes with varying amp selections depending on the global setting mentioned in the next point below. Changing the SIC dropdown value results in changes to these speaker page curve influencing values: Lo/High Freq, LF Reso/ HF Reso, LF Q/HF Slope.
• the global "Speaker Imp Curve" selection in "Setup">"Global Settings" which can set the SIC dropdown selection on the amp block speaker tab to be a specific value that does not change when amp model selection varies, or, to "default" meaning the SIC dropdown selection on the amp block speaker tab will change with varying amp model selections as described in the previous point.
• the "Auto Dynacab Imp" on/off selection in the amp block speaker tab, which, when set to "on" while in Dynacab mode in the cab block, overrides the SIC dropdown selection value with one that authentically matches the Dynacab selected in slot 1 of the corresponding cab block (ie cab1 corresponding to amp1, cab2 to amp2).
• the "Cab Resonance" parameter on the amp block speaker tab which can exaggerate or reduce the cab resonance "bump(s)" we see depicted in many amp block speaker tab curves.
• possibly some additional influence from internal non-user accessible (hidden) parameters as observed here (initially suggested as a possibility here (good radar!)), and with response from Fractal here.

 

[ben ifin]

Is the curve changing and the name not updating? If you click away and back to that tab did the name change?

Different amps have different output transformers and power amp specs, so the same speaker load will still cause a different response.

Its hard to explain ... so see the attached pics ... in order they are

1 = Dlx Verb Normal
2 = Supro Trem
3 = Wrecker Express
4 = 1959 SLP Treble

1



2



3



4



It might be hard to see in these pics .... but on my FM3 Edit Screen

=> 3 & 4 - the curves are absolutely identical
=> 2 - the curve in 2 drops across its range relative to 3 & 4
=> 1 - the curve in 1 increases a bit across its range relative to 2 but is still lower across its range than 3 & 4

Probably all normal and quite correct but got me curious

Ben

 

[unix-guy]

Its hard to explain ... so see the attached pics ... in order they are

1 = Dlx Verb Normal
2 = Supro Trem
3 = Wrecker Express
4 = 1959 SLP Treble

1

View attachment 142911

2

View attachment 142912

3

View attachment 142913

4

View attachment 142914

It might be hard to see in these pics .... but on my FM3 Edit Screen

=> 3 & 4 - the curves are absolutely identical
=> 2 - the curve in 2 drops across its range relative to 3 & 4
=> 1 - the curve in 1 increases a bit across its range relative to 2 but is still lower across its range than 3 & 4

Probably all normal and quite correct but got me curious

Ben

Looking at those curves closely where they are in reference to the grid lines, I don't see any difference.

You could drop them into Photoshop and adjust transparency so that all the grid lines are aligned and then compare... If you really wanted to validate.

 

[sprint]

Its hard to explain ... so see the attached pics ... in order they are

1 = Dlx Verb Normal
2 = Supro Trem
3 = Wrecker Express
4 = 1959 SLP Treble

1

View attachment 142911

2

View attachment 142912

3

View attachment 142913

4

View attachment 142914

It might be hard to see in these pics .... but on my FM3 Edit Screen

=> 3 & 4 - the curves are absolutely identical
=> 2 - the curve in 2 drops across its range relative to 3 & 4
=> 1 - the curve in 1 increases a bit across its range relative to 2 but is still lower across its range than 3 & 4

Probably all normal and quite correct but got me curious

Ben

When I pull up the same amps in Axfx3, keeping the "Speaker Imp Curve" consistent to "2x12 Lead 80" as you've done above, my "XFormer Low Freq" / "XFormer Hi Freq" values vary yielding different curves as expected. Makes me wonder what is different somehow in FM3 where it is keeping the same XFormer values for all 4 amps. I'd recommend checking to see if the front panel is reflecting different XFormer values than what you see in FM3Edit as you change amp models.

 

[Joe Bfstplk]

Different amps have different output transformers and power amp specs, so the same speaker load will still cause a different response.

This ^^^.

The curve you see is an amalgam of the speaker's impedence curve and the transformer's response.

Different transformers react differently with speakers, due to differences in the way they are wound, interleaved, etc., and differences in the mass, quality, and size/shape of the laminated steel used as the transformer's core....

 

[unix-guy]

When I pull up the same amps in Axfx3, keeping the "Speaker Imp Curve" consistent to "2x12 Lead 80" as you've done above, my "XFormer Low Freq" / "XFormer Hi Freq" values vary yielding different curves as expected. Makes me wonder what is different somehow in FM3 where it is keeping the same XFormer values for all 4 amps. I'd recommend checking to see if the front panel is reflecting different XFormer values than what you see in FM3Edit as you change amp models.

View attachment 142931
View attachment 142932
View attachment 142933View attachment 142934

Those definitely look different...

 

[sprint]

Those definitely look different...

the 1st 3 are anyway - the last 2 are close, but the XFormerLowFreq is close on the last 2 so makes sense. His parm values above are all identical - maybe FM3Edit is not showing the XFormer value changes? I don't have FM3 to test.