After some time with Sony XB90EX, I'd like to share my thoughts on them.
Build Quality
Build quality is very good. housings seem solid and are made from aluminium and ABS plastic (which is supposed to refine the sound). housings have pretty good and flexible strain reliefs, but they could be a little longer and more flexible. They are adequate imho and should be able to withstand daily abuse with ease - design of the reliefs is pretty good and they don't create any "hot spots" in the wire, in other words - they work as they should
also, they are finished beautifully and just scream classy
that's a definite plus to me.
cable itself is pretty thick, flexible rubbery cord with some grooves along the length. I don't really remember what these grooves are supposed to do, but I'm pretty sure they either lower microphonics, or prevent tangling. Truthfully, tangling is almost non-existent, but microphonics are sometimes annoying. they can be lowered by using the cable cinch, but it doesn't solve the problem entirely
It's not that bad, but still, it exists. good thing about the cable is that it is same thickness from the jack, to the housings, and inspire confidence. jack is really small, plastic, but has good strain relief and is L shaped, which I prefer to straight or 45 degree ones.
All in all, I'd say build quality is really good.
Comfort
although the drivers are one of the largest dynamic types used in iems (16mm) the design is really good and enables them to be really comfortable and don't cause any kind of fatigue in the ears even after long sessions of listening (I've had them in ears for 4-5 hours straight, without any issues with comfort whatsoever. stock, tips, while do not sound that good, are definitely comfortable.
Sound
Bass - members here named these iems the bass kings and I have to agree. bass is the foundation for the sound here, but it is not the regular kind of bass. there is no mid-bass hump, only the sub-bass is accentuated. the result of such tuning is that the bass never bleeds into the mids, and isn't bloated or offensive. I'm no basshead, but these sound pretty good to me. almost every other iem I've had, (except for meelec m21) had quite a big mid-bass hump and I always eq-ed it down. I don't have to do the same here. bass is controlled, and quite tight. it can become rumbly, but only when the recording calls for it. extension is the best I've heard so far, and can actually feel it vibrate to 15 hz or so, but at about 20 hz it is there sonically. As I've already said, the bass is big, but very controlled. it really feels like a subwoofer at times
I would suggest this iem to non-bassheads because while they are really bassy, they aren't offensive in any way.
Mids - these Iems are bass iems, but I actually love them because of their mids first, then bass
mids are smooth and quite detailed. they reproduce strings, piano and vocals really good. mid section is pretty flat, but there is a slight bump at around 6-6.5khz area. I would say that it is maybe 2-2.5 dbs, not more. One can always eq it out, and unlike many other iems, sound can be tweaked without much hassle on these. I just left it as is - it's not that noticeable or in any ways offensive. these will never get shouty or sibilant, so no problems there. nothing sounds unnatural, metalic, plastic or anything - timbre is really good and natural, well suited to acoustic music. I'm bad with all the terminology and describing the sound, but I'd say the mids are not thick, nor thin, quite detailed and transparent (if I can even use this word describing the mids). but this I can say for sure - the best and most enjoyable mids I've heard from anything, not only iems or headphones
Highs - highs to my ears are pretty sparkly, but there could be more sparkle I guess... they extend pretty good and then roll off. highs are detailed and never sibilant. this is a definite plus, because the thing I hate the most is sibilance. whole sound can be ruined for me just by that. not an expert on highs, so I can't add anything more. all I can say is that highs are more than enough for me and adequately detailed. they say that JVC FXD series are better in this regard, but I haven't heard them, so...
Sound stage, presentation
sound stage is big. I would say too big for some recordings
just try and listen to Dr. Cheskys new album, the drum and flute piece, and You'll understand what I'm talking about - it feels like I'm listening to the single drum and flute from far away. it could be described this way - imagine you are sitting in the middle section of a stadium and the flute and drum are positioned in the opposite ends of the field. they sound distant in this piece. Don't get me wrong - it really depends on the recording, because these can get really intimate and bring some instruments up close, but they can also send them to rare plains, far, far away
this works great with classical orchestra music, jazz and everything, except for weird recordings like the one I mentioned above
instrument separation and detailing is really good, and the wide and high Sound stage helps with it even more - sometimes I feel like I'm sitting in a concert hall while listening to dvoraks 9-th symphony, or I'm in the same room and sitting in the front rows on Art Blakey and the jazz messengers' jazz session. Instrument positioning is good, but still it depends on the recording. The drivers feel fast, fastest I've heard. busy rock passages are well reproduced and you can tell every string from each other.
overall, these are bass iems, but I actually prefer listening to non-bassy music with these. This is mainly due to its relaxed and laid back, immersive presentation and excellent mids, but also for the simple fact that majority of hip-hop recordings is of low quality and the bass sometimes is bloated. but good quality hip-hop sounds excellent! (nujabes, DJ Okawari, Tsuchie, Tech N9ne). great bass extension also helps with some classical pieces, like the Bach toccata and fugue, that really needs good bass extension for the organs, is really enjoyable with sonys.
I would say that these are quite good and at about 90-100$ are a good buy. I enjoy the hell out of them even now, as I'm typing
oh, btw, listen to this excellent piece with your XB90EX:
you can thank me later
edit:
I just discovered that youtube is an *******. I uploaded this yesterday, and it sounded almost as good as it sounded in the source flac, but just now I've listened to it again and it sounds like ****
could they process it more after uploading to reduce the size even more?