First Impressions: Fearless S8F, S8P, ACME8 & S10 Genie
S8F
Probably the "stand out" model in the entire Fearless lineup, next to the S5H for me. The S8F is very aggressive in its tuning. Its very clear with sharp and very defined imaging/attack. I'm guessing there's quite an intense rise towards 4k. As a result the lower mids can be positioned behind. Overall tonality seems to be quite uppermidrange boosted leading towards a clear and lean tone. S8F's bass is (perceived) neutral with fantastic speed and control. Huge leap from the previous models I've tried. Lower treble can be peaky and quite aggressive but it is decently extended. The S8F fatigued me out quickly, but it is pretty resolving. Only real downside is that the lower mids cant quite keep up. If not, really good.
S8P
Apparently this one is supposed to be the bassier model but I'm not hearing it at all. Sounded even more aggressive and energetic than the S8F. Sharper treble and uppermids which may kill. Even thinner than the reasonably thin S8F. Not sure what's going on here.
edit: S8P is indeed less bassy as reflected on graphs.
ACME8
Perhaps the most interesting technology of the entire lineup. Uses a crazy long low pass filter for the bass driver that's shaped like a maze. In practice, the ACME8 is warm but with nowhere thunderous bass. Vocals have a nice warm tonality, the best vocals in the entire lineup. Bass can be a bit slow and can be tightened up. Some may find it slightly wooly. Highs are smooth and extended ok-ish. Compared to S5H, it has less uppermids and more warmth. Would rather go with the S5H but they are different.
S10 Genie
The Fearless model that has the most unique tonality of them all. Clearly doesn't follow the typical Fearless house sound with boosted upper mids. The S10 Genie actually VERY LOOSELY (please do not put too much weight into my words) sounded like a Stax SR009 driven by a Blue Hawaii. Tonality and presentation reminded me of it. It's a lightweight sound which some may find that it lacks bite. Treble is actually well extended for what it is, perhaps the best extended in the entire lineup. Airy sound in combination with light weighted notes. Unfortunately, it's lacking in dynamics and can sound overly smoothed out in detail. I want to hear this one with more bass. Make it happen, Fearless.