Excerpt: Logic might tell you that the Sennheiser PXC 250 headphones can't possibly work—they're too small to seal out noise. But these compact, supraural (top-of-the-ear) phones with active noise reduction do a respectable job. They don't give you the tomblike isolation of the Bose phones, but they can do the voice-thinning trick too. In fact, these are the most compact active-noise-reduction phones we've tried that actually do the job.
Excerpt: The ultralight Sennheiser PXC 250 mini-headphones are exceptionally comfortable, but their undersize soft-ring ear pads may require some fiddling to seal properly. Our test unit's noise cancellation capabilities were excellent. Sound quality was in a class with that of the Bose QuietComfort 2 (reviewed on the Gear page), but low-end response didn't match that of larger over-the-ear models.
Summary: A typically high quality product from Sennheiser, the PXC250 headphones offer a good alternative to products from Bose if you're looking for something a little cheaper. The audio quality is impressive although it doesn't quite beat what's produced by some top tier IEM manufacturers.
Pros: Rich sound, great treble, good detail, comfortable
Cons: Battery pack is large, slight lack of refinement to the sound