OK, this is what happens when I start pushing things. Once I figured out how to extract the cabs from profiled rigs into separate cabs and export those as tarball backups, I started thinking:
A) "I wonder if the KPA's cab profiling results might be even better if performed separately from the amp."
Likewise,
B) "I wonder if the KPA's amp profiling results might be even better if performed separately from the cab."
If either A or B were true, then that might be a case for profiling the two items separately and combining them later, saving the result out as a new rig. Hi fi! So, I tried this, a task made easier by the "Preamp Defeat" switch on my ENGL. I also created a "null cab" to play with by plugging a loopback cable between the send and return and profiling that. It worked, sounded fine.
What I discovered though, was that the new rig I created, namely Profile(amp) + Profile(cab) was noticeably darker sounding than Profile(amp+cab). Hmm. Then, curious, I reloaded the (harsh and buzzy) no-cab amp profiled in Step B and then loaded the "null cab" into it expecting not to hear any difference. But there was - it still sounded harsh and buzzy, but some of the edge had gone.
Has anyone else tried this? Should we always be profiling the amps and cabs simultaneously for best effect, or is there some subtle bug?
-djh