Some notes on the new Fiio F1 IEMs based on a few day's listening using a Fiio X5-II.....
Sound is fine all around. Pretty balanced without overwhelming bass or treble though I'd say there is a bit of a loss of high end as compared to my current favorites - 1 More Triple Driver IEMs. In my opinion, the sound is really good across the board and there's really not more to say about it other than the performance for the price is outstanding.
The buds are reasonably small and definitely usable for going to sleep on a pillow which was my main purpose for them. I usually use Sony MDREX10LP IEMs which are arguably cheap but sound surprisingly good for $10 and are tiny so fit well in my ear while my head is against a pillow without mashing them into my head. These work well for that. The 1 More Triples are much longer and metal and can hurt if you're not careful.
My remaining comments are admittedly annoyances but I might as well voice my opinion in case someone out there finds them useful.
One of the selling points is the polyurethane cable which is "low microphonic" but, after using these I can assure you they are no less microphonic than anything else out there using some sort of rubber. The low rumble of the cables against my face, chin, clothing, etc. easily makes its way into my ears. So these are no better than any other IEMs out there. The ONLY cables I've ever used that did not have annoying microphonics were the cloth-covered cables that came with the Microsoft Zune. Those were practically silent.
Also, Fiio says they have "clear left/right channel identification marks" and that's not true at all. You can hardly see the L and R unless you intentionally turn the IEMs over and have light hit them just right. What's really irritating is there's no molded-in dot of some sort so you can tell which one is left or right by feel. Just one tiny little raised dot would do. Why they left it off is beyond me. So you have to run your hand down the cable to see which bud is connected to the in-line controls which indicate the right side. That's the only way even when you grab them in full daylight because, although the cables are tangle resistant, they still overlap or twist enough so you don't readily know which one is connected to the controls. A molded in dot would really help here.
In reviews and on Fiio's website, you can see there's a movable cable cinch above the Y so you can slide it up and tighten them around your chin but mine is missing that. Don't know why. That's an odd thing to be missing. No, it did not fall off in the box.
The inline controls did not immediately work with my X5-II. I pushed the buttons and nothing happened. I had to unplug/plug it in a few times after which they finally started working. Not sure that's an IEM or X5 issue.
The controls also work as expected with a Samsung Galaxy S7 though I'm going to complain about the lack of a raised dot on at least one of the buttons - specifically the middle one. Pressing the upper or lower ones is a piece of cake but the buttons are so well levelled next to each other it's difficult to know when your finger is on the middle button so I find myself sometimes pressing the upper or lower one instead. Placing a small raised bump of some sort would remove the ambiguity. I have learned to run my fingernail along the face of the buttons so I know where the gap between them are so I know for sure I'm over the middle button. Annoying to me only maybe.
So performance-wise, they are great. These definitely make the music sound like I believe it should so I never have to think about "Hey, that didn't sound right. What's wrong?" But some of the ergonomics are not as good as I personally would like.
Recommended for great sound with some points off for ergonomics.