In a nutshell, baby HD25s
Pros: Neutral, accurate sound; small, portable, comfortable
Cons: Isolation isn't the best, annoying volume control
The PX200-II are a nice little set of portable cans, maybe the best Sennheiser has out right now in their budget lineup. Amazingly enough, the Headroom frequency graph does not lie: the general sound signature is the same as in the venerable HD25-1, with a bit of treble roll-off.
I really enjoyed these cans while I had them. The sound is smooth, with restrained and very fast bass, once you get the earcups in the right position. Some people might find the bass quantity lacking, but there's no doubt about the quality. The mids are upfront and very energetic, which, coupled with a fairly tight bass, might put some people off, as the overall sound can be dry and a bit cold. Detail retrieval and presentation are just ok, nothing exceptional. On some tracks they can sound a bit boxy or congested. Highs are a bit too recessed for my taste, or just not detailed enough, as every cymbal note on these sounded the same to me.
Build quality is very good, these things are ment to last quite a bit. The only problem could be the cable, especially at the strain reliefs and the volume control - quite an annoying feature, actually, because you have to clip it to something at all times. If not, the cable will drag the left earcup down quite a bit.
Comfort is very good: the earcups barely cover half your ear, and the clamping force is just right to keep them on your head without it becoming bothersome. Even in summer, these can be worn with minimal discomfort.
Isolation is ok, but I didn't really think it was enough for loud buses or the subway. It might be good for walking or jogging, but you will hear what's going on around you more than you'd want to, even with music playing.
Overall, I'd say this is a good alternative if you've ever wanted the HD25 and cannot afford it just yet. Bassheads, stay away from this one.
They look nice, and are really small and light. Comfort is a bit lacking at first, but when you get used to it, it gets better. Also, they are relatively affordable. Build quality is great, expected from Sennheiser. isolation is average, but what else do you expect from a small, sealed, pair of cans? Overall, the sound is good. The highs are slightly rolled off, but are smooth and never fatiguing. The mids are slightly boxy, but satisfactory nevertheless. the bass was a weak point of the first px200's, but because they now have a better seal, they're tight and weighty. Overall sound signature is balanced and natural, and soundstage is better than you expect from a headphone like this.