I see the AXE-FX guys starting to get into this impedance curve effecting power amp frequency response thing. http://forum.fractalaudio.com/axe-f...e-release-monster-speaker-resonance-page.html I have read the whole thread and couldn't find a single impedance plot of a real 4x12. Just wanted to tell them that a 2x12 is around 120Hz and as I read a 4x12 is 110Hz and not 75Hz like in free air. My first attempt was based on that (75Hz) but now its 110Hz as in a 4x12. To go higher from 75Hz to 110Hz I had to unwind the inductor from 20mH to 11mH. It made the re-amped dummy load resonate with my 2x12 (110 and 120 are close enough) so the natural springy bouncy feeling is back. Now when I reamp the dummy into a solid state power amp the sound is indistinguishable from the straight to speaker sound. But I'm still determined to make it 1:1. Raise the Resonance peak impedance to match, and raise the highs impedance a little too. Soon, I promise. Here is mine with the latest tweaks: Purple is my Framus 2x12 (120Hz Fc), Green is my Dummy Load (110Hz Fc). Useful Info. If anyone thinks they can fix this curve with an EQ after a simple Resistive dummy load is wrong. A tube amp (poweramp) is a "Constant Current" amplifier. It means the only thing that changes is the Voltage and it has a limit (B+). This limit is when the poweramp has no more voltage to swing and amplify the signal resulting in = Clipping/Distortion. Guess what frequencies get to distort first? That's right, the Resonant peak and the Inductive treble hill (They are higher in impedance therefor higher in Watts). As you go higher on the master volume knob the middle section "catches up" with the already distorted resonant peak and the Inductive treble hill, eventually resulting in a flat line. (I have tested all of this). This is CRUCIAL to how your amp sound and distorts at any volume, and you can't fake it with any kind of post EQ. It gets some famous attenuators out of the game right there.