Lol, so you changed a kone for a 70/80 and tought it was less "fizzy", something must have gone really wrong, as putting one of the "fizzyest" speakers on replacement doesnt sound like a solution.
No, for four years I have been using a Fender Mustang III loaded with a Celestion G12T-100, plugging the monitor out of my Kemper into it's FX Loop return. I purchased a Kone in early May, 2021 to put in a 1 x 12 open back cabinet I was having built, the Kone arrived in three days but I just received the cabinet and a new power amp last week, so outside the 30 day return window on the Kone. I spent the better part of three days trying every conceivable combination of settings on my Kemper with the Kone to no avail, so I loaded the G12T-100 in the new cabinet for now until I purchase a replacement. It's a temporary solution working with what I have available.
I have that same speaker and have been using it during rehearsals. KPA monitor out into the return of the Mustang III. I've got a Kabinet sitting here, waiting for me to finish my personal 'camplifier' build. That should be done within the next week.....but I've been saying that for a month now.
With monitor cab set to off, you're right in saying that speaker (Celestion G12T-100) is not horrible. At least for clean to mid-gain stuff. Rather generic sounding....but given the amp it's for that's expected. Higher gain and it starts to get become indistinct. More so than speakers meant for that purpose.
Something had to be 'off' with your Kabinet. No way a G12T-100 should outperform it. People swapped those speaker out constantly when the Mustang III's were available new.
I wholeheartedly agree, I really believe I may be unlucky enough to have received a lemon. This Kone sounds nothing like demo videos on YouTube, and that's including lower quality videos recorded with a phone, the sound quality in those videos are fantastic compared to my Kone live in the room, which sounds similar to an old handheld transistor am radio in the mid to high frequencies and very prominent, almost overwhelming bass frequencies. The G12T-100 outshines it and that absolutely should not be the case, I think something must be wrong with the high frequency driver of this particular speaker. It's to late to return the Kone I purchased and I'm not willing to put out another $180usd for another Kone at the moment. It's disappointing as I was really looking forward to taking advantage of the Kemper + Kone technology, but this is my first mishap since plunging into the Kemper universe four years ago, no trouble with my Kemper or with the free updates I've installed and those were probably worth the cost of the speaker.