Foreword: This unit was kindly loaned to me by Thomas of @NCM. I specifically requested it due to my love for hybrids. The Bella is their hybrid flagship, sporting 8 BA drivers and a single dynamic woofer, a combination that seems to be a favourite amongst Asian IEM makers (like AAW and Rhapsodio, just to name two). Frequency Response Somewhat U-shaped response? Sub-bass emphasis, 6k "brilliance" peak and a last, tiny 10k peak for definition in the upper percussions. The 2-3k bump with the 5-6k peak heavily indicates a TWFK stack being used. Impulse Slight rubberbanding which suggests a mild incoherence between DD and BA. Subjectively, I don't hear anything out of the ordinary. Zeroes out pretty fast with little linger. Subjectively, it certainly sounds "fast" (via my own overactive imagination), good clarity and little smearing of individual notes. CSD CSD check passes out. No weird issues. (For weird issues, see Rhapsodio Zombie and Kinera H3) THD Surprisingly low distortion, even in the midrange where the BA's third order is expected to kick in. There is still some third order but comparably lower to other hybrids that I've measured. Impedance Reactivity Biggest changes are in the bass regions. Expect increasing bass volume and note density with increasing OI. Personal ideal OI lies around 5. The 5-6k peak can get a little intense for me and an increase the bass/lower-midrange certainly helps in counterbalancing that. Plus, I like my IEMs on the thick side. Additional Notes: Bass is the strong point, though admittedly not as good as the CE-5 in my opinion. The hits are a little fuzzier and lacks definition. Sub-bass rumble also doesn't sound as "clean" in comparison. However, in the grand scheme of things, the Bella's bass is well done, at least managing to somewhat avoid midbass bloat and focusing more of its energy in the lower registers.