I got the RY4S UE cable version for a while now, and just wanted to add my thoughts, comparing it to my most used earbud at the moment, the Willsound MK2.
I got it during the 11.11 sale, and it got here at the beginning of December. I used it for a week almost constantly, and then mostly put back the MK2 and forgot about it until tonight, when I pulled it out again to see what was bothering me so much about it.
It has a nice punchy sub-bass, and no mid-bass bloat. This gives it a nice punchy bass that adds weight to instruments that need it without hindering the clarity. I feel it has more sub-bass than the MK2, but less overall bass, but it is probably just a perceived effect due to less distractions in the sub bass. As a result, the imaging is less fuzzy on the RY4S, but everything sounds smaller, like the instruments are less heavy. There is less weight on the instruments on the RY4S than on the MK2.
The mids are quite recessed. I originally found the mids on the MK2 recessed, coming from very mid-centric IEMs, but the RY4S takes it up a level. The voices sound farther away, and while they still sound clear, they definitely don't sound as detailed as the MK2. Some instruments that I hear clearly on the MK2 appear very faintly on the RY4S. This also affects the timber, which is what bothers me the most. The mids on the RY4S sometimes sound "plastic-y"...I don't know how else to put it, but sometimes it doesn't sound like a guitar, but more like a keyboard playing a guitar, if that makes sense.
The highs are less well extended on the RY4S than on the MK2. Some air is missing. That being said, there is plenty of detail there, cymbals sound correct, and it never gets piercing. The MK2 sometimes gets up a little high, but I do have to say that sibilance doesn't bother me, and I am kind of a masochist when it comes to highs.
Overall, it sounds like I am being negative towards the RY4S, but really, it is only because of how amazing the MK2 makes everything sound. The imaging is very holographic on the RY4S, and other than the mids weird timber on some songs, and a lack of air, I think that the RY4S does a lot of things very well. The bass is very nice, and one of it's best attributes.
I also think that the RY4S look and feel really amazing. They really feel premium. The cable is beautiful and doesn't tangle. The plug is a really nice size and fits really well. It is really beautiful. It looks much nicer and more refined than the DIY style and feel of the MK2. One thing I noted though is that the plastic on the shells of the MK2 seem better, they seem thicker and less brittle.
I think I would recommend the RY4S to a friend who wants to try a nice earbud without spending too much, but for anyone with a pair of earbuds over 50$, I don't think they are worth it.