briefly here's what I've found.
* none of the IEMs were anything like as good as my AKG K271 headphones. even though some cost considerably more. This worries me. am i doing something wrong?
* UM1
the UM1s have a tight focused midrange, so far so good, they have very little bass and very little treble over about 8k. they have a fatiguing peak at about 3k.
If i EQ them quite a lot with a precise digital EQ they sound almost OK
* UM2
the UM2 sounds like the UM1 but with much much more bass. the 3k peak is less noticable, because the bass sort of counteracts it, but it is still there, the highs are the same as the UM1. sounds better than the UM1 overall, but with EQ i prefer the UM1. the bass on the UM2 is muddy and if you turn it down its still muddy, wheras the bass on the UM1s is tight, but theres very little of it, turn it up and its still tight tho.
it doesn't respond as well to EQ as the UM1, perhaps its faults are not just frequency respose , but include other problems like crossover related phase inaccuracies, which eq can't fix?
* atrio
these have a sort of smoother and more natural sound, less forward than the westone IEMs. but they have massively far too much bass which overpowers everything else. they also have a fatiguing midrange peak, a little higher than the westones, maybe about 5k, and less pronounced.
both westones fit very comfortably and sealed well, the atrios were also ok in this regard, but not quite as low profile in the ear as the westones