Westone UM1

Pros: excellent detail as well as bass, comfort vx rival products, virtually no microphonics

Cons: soundstage iffy compared to circumaural headphones, high end roll-off

Summary: The specifications for this product state that the frequency range for it begins at 40Hz. I used a tone generator, and discovered that it is actually ~27Hz, which explains the wonderful, tight bass. The high end begins to roll off at 16kHz, less than I would like, but higher than necessary.

Performance: The UM1 meets or exceeds my expectations in all categories; the isolation is great (using short Comply tips), allowing it's resonant, though not boomy, bass to be quite present. On IEMs with strong bass, the common problem is lack of clarity and range in the mids and highs. While these won't satisfy the ultimate detail-head, they do do a more than adequite job throughout. They also seem easy to power, requiring no external amp when used with the Apple iPod.

Comparison: I have tried the Shure E2c, Etymotic ER6i, and the Altec Lansing iM716 (which according to all accounts uses the same driver as the Etymotic ER4).

E2c vs UM1: No contest. The E2c to me had a lot of bass, but it was muddy bass. These are much cleaner, and don't sacrifice the detail of the mids and highs to achieve their excellent bass. Comfort is also exponentially better, as these are much smaller.

ER6i vs. UM1: Slightly closer, but not much. THe Etymotics certainly have a cleaner more detailed mid/high range, but have a severe deficiency in the lows. I'm not saying the UM1's are your hip-hop bass heavy phones, but they seem much flatter across all frequencies. Comfort is close, though microphonics are less in the UM1

iM716 vs. UM1: I love the HD/Bass selector for the 716, which takes the headphones from a sterile detailed sound to a more fun sound, but I still prefer the UM1. In this category, I'd go with the UM1 still. It's basically the difference of the Sennheiser vs Grado sound, one being warm and inviting, the other being more sterile with better resolution. One factor to consider is that the 716's are harder to power, and an external amp helps them significantly with portable devices.

Hopefully this was helpful...