Pros: compact size, minimal microphonics, great sound
Cons: star tips might be a bit painful
disclaimer: I'm still pretty new to this whole 'audiophile' thing so my impressions probably are not the most accurate. i don't own any so called 'high end' audio gear so all my comparisons will be done with respect to sounds in real life, against what instruments actually sound like in a band or when singing. all tracks used are either 320kbps mp3 or lossless CD rips on an iphone 4
build: build wise, i have no issues at all. i've been using them almost every day for the last 8-10 months or so, to and from school and everywhere in between. I've used them till the wires have curled into the memory wire-shape behind my ear, but the whole thing-cables and all, still working fine. their small size plus the compact case makes it easy for me to wear just about anywhere cos they're really comfy and easy to store. my only *minor* gripe is that the star tips felt slightly uncomfortable for me, but that's just personal preference.
sound: the um1 was my first pair of BA driver earphones so i had no idea what to expect, especially from such a tiny thing, but the um1's punch way above what i thought they would. As a whole, its really detailed in replicating all the sounds in whatever track i toss at it, but I'm the kind of guy who likes to break things down so here it is...
TREBLE- really crisp sounding, sparkly highs that generally sound great with anything. listening to violin or other string instruments, the resonance of the highs can be heard, albeit slightly muffled and lifeless compared to the real stuff, but hey its good enough for me. the defining moment for me was when i listened to 'phantom of the opera' by sierra boggess and ramin karimloo, the last high note that sierra hit did not sound shrill at all, although the ring that such highs make naturally were not exactly there, still, the um1 performed incredibly with that track. only gripe i had was when listening to the electric guitar, riffs and shreds tend to sound either really muffled or shrill, but the rest of the time it sounds fine.
MIDS- what i feel really make a song come to life... the um1's mids are incredibly analytical in the sense where i can hear all the details in band music with the instruments playing and stuff, but i would have preferred if they had a bit of a warmer sound to them. what that means is that in tracks with a very strong vocal presence, although the vocals sound fine, they lack the warmth and emotion that you would hear in a live performance. where the mids really come through though is when they are given things like piano or acoustic guitar pieces, with the kind of rich creamy sound
BASS- I'm no basshead, but like many i love a good bit of oomph in my tracks. the bass of the um1 is solid all the way, although it might be a bit more muggy sounding at the lower sub-bass end of the frequency range. still, and bass guitar lines are clearly heard, controlled but impactful; same goes for the drums, i played a couple of drum solos on the um1s and it replicates the sounds fantastically, toms and kick drum both. even in rock music, when there is so much going on in the highs and mids, the drum line can still cut through and make itself heard. only problem is when you have both the bass guitar and drums at the same time, the um1 seems to 'sacrifice' one sound for another, which tends to cause both parts to meld into one slightly messy lump of sound, but maybe thats because its only one driver, i have no idea how the um2 or um2x sound so...
in general, the um1 is a very good pair of earphones because they can represent all the main parts of a piece of music with pretty good detail. instrument separation is good all the way to the bass levels, with minimal mushiness in the lower bass frequency. however, as previously mentioned, the um1s do not really show all the nuances and overtones of natural sound, which is not that big an issue when you look at the price of it and its quality. i am very sensitive to this kinds of 'nuances' so some might not even notice the difference, especially if you haven't heard the physical instrument. on the other hand, this inability to reproduce all of the sounds you hear could be a good thing because the um1s are very forgiving of all but the worst audio formatting, giving you decent quality sound even down to 128kbps, so if you are like me with a music collection of everything from classical to punk rock and 128kbps to FLAC, the um1s are a great pair of earphones for general listening, plus they sound perfectly fine un-amped too. :)