I've been using my Powerhead for a few months now, most of the time with a Celestion loaded closed back guitar cabinet and the cab simulation deactivated on the monitor output. Of late, I've been experiencing some bad tone days and haven't been able to figure it out until today.
I created all my patches through the cab but also use the headphone output, main outputs to PA and also main outputs to in ear monitors. I'm mostly using profiles from The Amp Factory and despite creating some great sounding patches, i end up relying on a small handful that sound good through everything.
My eureka moment today came when i considered what my favourite patches had in common; the profiled cabinet. I realised that a patch i make with a Marshall type cabinet in the profile still sounds great through my cab, as it is very much like a Marshall cab and also sounds great through the main outputs. If I select a profile created with a different type of cab, that's when it starts to go wrong. If I find a Vox profile that sounds good through my cab, it doesn't sound so good through the other outputs. You're always going to tweak an amp to suit the speakers so if you profile with Alnico Blues, you'll want to tweak it when using Celestion V30s but you'll also be adjusting the main outputs as well. As the monitor and output EQs are global, there's no easy way to fix it between patches.
I've accepted there's always going to be a compromise when using the Kemper the way I do, if I want to mimic a ton of different amps I'll need to stick to using a FRFR but I really don't need that, I just want a good selection of tasty tones. Ultimately, once the drummer starts, the subtleties of my tones become rather pointless!
I've now changed my patches by selecting profiles that sound good through the cab and the main outputs. It didn't take that long and it's always fun creating new patches on the Kemper.