Let me preface this review by stating that I am a huge Sennheiser fan and they are my favorite headphone manufacturer. That said, I am disappointed with these phones. I believe Sennheiser has managed to change nearly everything for the worse compared to the original PX100. Here's why--
--sonically, I find them worse compared to the original--they sound slow, congested and have an accentuated upper-bass. I found the original PX100 to be the most detailed and balanced portable headphones available. With the PX100-II the detail is still there, however, it's no longer as natural sounding or as exciting. The sound slow and have an overly thick texture. The tonal character is a little overly warm as well, no surprise given the boosted upper-bass.
--the single-sided cord is more of a weakness than a strength. Most other portable headphones have cables going to both earcups which makes the headphone cord lay in the middle of your torso and keeps the cord from brushing your arms and hands when walking/running. However, the single cord of the PX100-II orientates the cord overtly to the left. This can cause problems if you keep your MP3 player in your left pant's pocket (as I do). Unless I route the cord under my shirt/coat or use some kind of clip to keep it in the center of my body and find that it's continously getting in the way when I walk or run.
--the cord is overly textured causing it to stick to your skin. This can cause issues when you need to reach into your pocket for your MP3 player and the cord sticks to your fingers instead of allowing them to brush past.
--the PX100-II are over-built. Compared to the original the headband is thicker (both in width and depth). The points where the headband connects to the earpads has also been strengthened (and the headband now sides further away from the earpads on the right and left). Because of this beefing up the PX100-II is now, however slightly, more bulky and heavy than the orignal. And I can't help to ask; to what end? I've never heard of anyone who complained that the original (or other competing headphones, like the PortaPros) were overly weak and flimsy. Now, due to the thicker headband the phones are less comfortable to lay around your neck when not in use and are now even more uncomfortable to try and slip underneath a hat or a beanie. The original was robust enough. Now there is extra weight and size with no benefit.
--they didn't fix the serious flaw of the orignal PX100. Look at the reviews of the origina PX100. The one thing, I will repeat ONE THING, that people consistently complained about was the weak 1/8 jack used to plug the phones into the source. Over time stress caused the cord to seperate from the plug and sound to cut out in one or both channels. Senneheiser did nothing to correct this problem with the PX100-II. The plug is exactly the same and people are already starting to experience this problem with the PX100-II. Given that they went through the trouble of strengthening the headband (needlessly so) why was no attention paid here? That's either negligence or incompetence (sorry for the harsh words but come on...)
Really, there is nothing that I like about the PX100-II more or even as much as the original PX100. It wouldn't be such a big deal if the original PX100 was still available but it has been discontinued. I recommend thinking twice about purchasing these headphones and that's something I rarely say when it comes to Senneheiser.