Thank you!
Yeah, I've tried it with the real cab! Both approaches, the synth with the sine wave and the peak filter but I am not sure if I hear the cabs resonance or my rooms resonance, hence my question.
I am aware of the valhallir cab, but as you already stated, not sure about front or rear loaded, also not about the production date of the cab, might be an older one (Diezel redesigned their cabs a while ago).
v30s are listed with 75 hz , k100s with 85 hz as resonance frequency, so around 90 hz for a x pattern cab might be right, considering we are adding about 10% as stated in Cliff notes.
I was just wondering if someone has measured it or has a better idea than my lousy guess.
Anyway, thank you for the input!