Fiio FA1 VS Fosi Audio IM4

Youtube Video Summary

Fosi Audio IM4 brings a beryllium-coated single DD in a compact shell with thoughtful venting that behaves almost open-back for comfort during long sessions. Build is surprisingly premium for ~$100: a small, well-finished nozzle that grips tips, a light but durable cable with color-coded channels and a working chin slider, a tidy case, and tuning nozzles (black/gold) plus multiple tips. It’s the kind of fit and finish usually saved for pricier sets.

Tonally, this is an engaging, warm-rich tuning with elevated sub-bass, good texture, and plenty of detail—not a neutral reference. There’s energy in the 2–4 kHz region and a bit of 5–6 kHz bite that can read as “cat-ear” presence, trading strict smoothness for extra soundstage perception and clarity. Versus the many neutral options at this price, IM4 feels more characterful and fun; think closer to sets that use a staged upper-mid/treble contour than to flat targets. Filters/foams or a touch of EQ can gently tame peaks while keeping the lively character.

On the scoreboard: bass 7/10 (clean shelf and punch), mids a touch recessed versus a neutral target, treble lively with agreeable detail, and stage/detail notably good for the class. Overall, a well-built, fun, and slightly audiophile-tuned single-DD that will appeal to listeners who value texture and excitement over strict neutrality—plus rare build quality and extras at this price make it a solid value.

Youtube Video Summary

Quirky name aside, the Fosi Audio IM4 brings a 10 mm beryllium-coated single dynamic driver with a tuning that reads more cohesive, clean, and neutral than bass-bomber. Music floats with a great soundstage and a velvety midrange, giving smooth-jazz and vintage recordings that “swirling around the head” vibe without getting muddy. Hints suggest a price under $100, which would make this one of the stronger performers in the budget bracket, especially given the unexpectedly premium build.

The shells feel like they were machined from the same stuff as Fosi’s amps—weighty, thick, nearly indestructible metal—with a solid 3.5 mm cable (no 4.4 option noted). Accessories are unusually thoughtful: two tuning nozzles (black = lightly damped; brass = no damping) and three styles of tips. Swap to the brass nozzle and treble detail jumps while bass eases off, which can turn the top end a touch spicy for some; stick with the damped setup for a smoother, “just be good” balance. Add a decent case and, if the rumored price sticks, it’s a high-confidence recommendation in the sub-$100 class.