A new player in the market - KB EAR - would love to take our attention off of KZ/CCA for once. Clearly, KB EAR are not playing in the ultra-budget tier, but instead are going for the mid-budget (around $30-$50), and the F1, along with Opal, are their first offerings.
The F1 are simple-looking, well-built and good sounding earphones that outperformed my expectations from a single-BA pair. That been said, the sound isn't quite universal, as those BAs have a particular metallic timbre that is so common in BA earphones, especially noticeable if you're used to dynamic driver or hybrid earphones. Also, the bass extension and impact can't compare to earphones equipped with dynamic drivers, which make these earphones not so suitable for electronic music or anything with a beefy bassline (like folk rock).
Considering F1's price point, there are clearly earphones with more universal sound signatures that can outperform the F1 even at a lower price, the Senfer DT6 being a perfect example of such earphones. I wouldn't be surprised if I found out that the included cable (which is an excellent cable) makes up a decent portion of that price tag.
The housings have no channel markings, but since the housings have identical shape, you can connect them to the cable (which, of course, has markings) however you like.
Comfort & Fit
Although these earphones have nothing ergonomic about them, I had no issues with using them and keeping a good seal for prolonged listening sessions, mainly due to their slim size, light weight and long nozzles. However, I wouldn't expect these to keep a perfect seal while you're on the move, since the ear tips are the only thing keeping them inside your ear. I would guess that these were designed for a comfortable stationary listening. The sharp edges weren't a problem comfort-wise, as they weren't pressing against any part of the ear.
Lows / Bass
The bass is, indeed, impressive considering the fact that these earphones only use a single tiny balanced armature per channel. However, this particular BA has its limits, and the bass (especially the sub-bass) quality, depth and impact just can't compete with dynamic drivers, or at least some larger BAs designed especially for bass reproduction. I even managed to get the bass to heavily distort while I used them with my smartphone, especially on higher volumes - that definitely limits what kind of music you'd be able to enjoy with these earphones.
Mids / Vocals
The mids are very precise, although maintain slight metallic tint that I found rather common in earphones with BAs. It's not severe, and quite frankly way more impressive than most budget-level BAs I've heard so far when it comes to clarity and level of detail, and it's mainly a matter of getting used to in this case. I also have to mention that I find the mids to be slightly edgy and I had to turn down the volume sometimes to keep the shoutiness at bay.
Highs / Treble
The treble is bright and can sometimes cause some pierce or sibilance on vocals, something that can be controlled with different ear tips to some extent. Despite that, the highs are highly detailed and crisp, and I wouldn't have expected any less from good quality balanced armatures. Great treble for fans of analytical sound.