Foreword: FiiO has graciously provided me a unit upon my request, in exchange for my honest opinion. The F9 is a "budget" triple-driver hybrid IEM that seats itself in the highly competitive $100 space. Frequency Response Impulse CSD THD Analysis V-shaped response, notably its recessed mids. Quite distant from the rest of the frequency. Midrange (notably vocals) don't have a lot of layering ability and lack weight. Singers feel like they are constantly using head voice, resulting in a thin and sometimes shrill sound. Pretty bright, could see it being sibilant for some. It's pretty borderline for me; then again I'm quite sensitive to high frequencies. CSD shows bass decaying closer to the typical BA than its DD brethren. Bass is also skewed towards the midbass rather than the sub. THD numbers aren't stellar but also not horrible. I've seen worse. First impressions, it's pretty decent at $100. Definitely bests the 1More Triples but if given the choice I'll stick with my tried-and-true GR07 anyday. Upcoming will be measurements for impedance characteristics and tiprolling.