Hi AxeIF,
I intended to get the new MF10s set up in 10 minutes and then spend 10 minutes playing with them this evening. Set up was more like 5 minutes, and then I spent 30 minutes comparing them directly with the Fearless F115 at relatively high volumes (my ears are ringing a little now).
I am really impressed with the MF10s, and definitely don't hear any of the nasal or Dobro-like tones you talk about. Of course they don't have the open top end of the F115, or the same FRFR qualities, but the the Fearless is a big cab, maybe with an "over-engineered" crossover, and full acoustic separation of the 3 drivers within the cab. So it is not only remarkably flat, but preserves phase relationships in a remarkable way across all frequencies.
I am very happy to say that the MF10s compare favourably with the F115 rig, with the main noticeable difference being the relative "sparkle" of very clean or "glassy" tones. For those, the F115 comes across as very open sounding, and the MF10s are not boxy, but definitely attenuate the top end a little. They more than compensate for this by punching very hard, and very faithfully, in the mid range. While I was experimenting with some aggressive fuzz tones with a "chopping" tremolo and flanger quite loud, I suddenly remembered how I last blew a mid-driver in the F115, but the MF10s were still blasting loud and proud, without once lighting the clipping diodes at similar volume.
So I think in fairness, the MF10s are not quite a "true" FRFR speaker in the same way as Fearless F115, but I like them. I have mainly used closed back 4x12 cabinets for most of my guitar-playing life, and they imitate that sound and feel very well, and of course with the advantage of not "beaming" treble down a narrow line that focuses more than 20 feet in front of the cabinet. And I think they are going to be loud enough for most stages that I play on, but we'll see over the coming years!
I didn't spend very long comparing the MF10s to the RCF 732s, partly because the MF10s are immediately more "guitar oriented" in tone, and partly because I cannot remember if I should have been using Output 3 of the Axe FX III. I went with default Output 3 to the MF10s, but as a copy of Output 1, and it sounded quiet, dark and kind of miserable. I was a little worried that the MF10s might be truly terrible sounding speakers, so I borrowed Output 2 from the RCFs. Problem solved! I'll look into where I went wrong with using Output 3; maybe it's intended for 4CM or something.
After reading your comments I kept the packaging for the MF10s just in case I needed to send them back. I think it will more likely be in the cardboard recycling next time they collect.
I wonder if your one might be faulty in some way? My first impressions are of incredibly capable speakers, giving great response across a range of amp and effects settings, and definitely preserving the "feel" in a similar way to other good-sounding monitoring solutions in direct comparison. I have yet to play them alongside a loud acoustic drum kit, but I'm pretty confident they will keep up admirably. The low mids are so far absolutely "sh1t-kicking", with surprisingly deep lows for 10" speakers, even when pushed.
Liam