Pros: sound just blossoms, full sound stage, gobs of air/transparency
Cons: takes some getting used to
I personally prefer the sound of the "Westone" series to the "UM" products. I use my IEM's for listening to pre-recorded music. The sound of the UM series is very good, but the WESTONE 4R is the closest I have come to the sound of my FOCAL speakers. While the sound was pleasing when using the COMPLY foam tips, the UM56 custom tips took everything up a level. The bass is still prominent and powerful but just a tad more solid. It's like a touch more pillow in the kick drum and a little low-mid rolled off the bass guitar and a slight bump across the low frequency spectrum. The mid-range which was stellar to begin with became more controlled as well. Transients were more defined and notes more delineated. Staccatos were sharper and legatos were smoother. Highs disappear into the stratosphere. There is no grain, edginess, aggressiveness, etc. The high end is reminiscent of the QUAD ESL speaker. In summary, the UM56 tips just allow you to hear more of what the armature is doing.