The sound on these headphones has a bit more high frequency and bass boost than typical Senheiser headphones. However, unlike many headphones with this sort of a boost, the midrange still comes through with a clarity that is classic Sennheiser. The overall effect will probably be quite pleasing to people who think that Sennheiser headphones lack enough bass.
There is also a volume control device on the cord which is identical to what's on the Sennheiser MX-500 earbuds. I don't make use of this thing since the cord is only about 3 ft. long and any device you hook it up to is going to have a much better volume control button, but some people might like this.
These headphones are almost like earbuds, except that the way they fit into your ear keeps the ear canal open so that outside sounds and noises still get in. This has its pluses and minuses of course. If you need to hear what's going on around you for safety or work reasons, that's a plus, I suppose.
The headband is EXTREMELY light and loose. The plus is that I guess you will not feel any pressure at all on your head or ears from the headband, but the minus is that they do not have enough tension on them to pop the speakers into position in your ear by themselves. You will have to push the speakers in and hope that your ear anatomy will fit these rather large buds and that the fit will have enough friction to hold them in place. If they fit, then they sound great. If for some reason you can't get them to seat properly, these headphones will sound either tinny (too far away) or muffled (pressed too close in). The amount of bass you get will also vary with how well seated you can get the speakers into your ear.
So I'm fairly certain that some people will write in panning these headphones for the simple reason that they don't fit and so don't sound very good. But they do fit me just fine, with a little jiggling, and sound great.
I also have the Sony MDR-A44L, which look similar. The headband on the Sony is slightly tighter and is just about perfect for holding the earphones in place without causing discomfort. The Sony has even more bass, but the midrange lacks the clarity of these Sennheisers.
Overall, despite the loose headband, I prefer these Sennheisers to the Sony, but I should note that I have used Sennheiser headphones for years and prefer their sound. It's just whatever you are used to hearing.
I've ordered this headphone expecting to get the best of this type of headphone design (usually good for exercise) + the excellent reputation of Sennheiser for good sound quality. Well, the sound is indeed good (thus the 3 stars), as anyone would expect from this manufacturer, and it is really lightweight as the name indicates, but the design of the over the head support is too flimsy for jogging (it does not apply the minimum necessary amount of pressure to keep the thing tight in your head) and the ear plugs are too big (at least for my ears). The result is that is definitively not for jogging, since it will fall out of my ears every few seconds.
I have a Creative Zen mp3 player that runs off an AAA battery. With my Sony MDR-W20G headphones, I had to run the player at max volume (40)to get the volume I wanted for jogging (same with my old 64k Yepp). The Sennheiser is plenty loud at 30. It is difficult to find headphones with high enough sensitivity for this type of application -- the Sennheisers are great.
I love the seinnheiser brand and quality so i disregarded the reviews about the headphones not staying on your head during workouts. however, i use them for running and working out and its true, they pop out of your ears all the time when exercising. Also, noone has mentioned that there is a volume control on the wires. This would be great if it worked. I constantly have to make sure that it doesnt get wet and find myself adjusting it all the time to get sound out of the headphones. Now its so shaky its not even worth wearing. Great sound but i would get another pair
The Sennheiser PX-10 "in the ear" headphones are well made and attractive but they have very poor high frequency response. Percussive notes such as symbols are barely audible and orchestral instruments like violins sound muddy. I don't recommend these phones for the audiophile. The Sony MDR-W20G, on the other hand, have excellent frequency response, are less expensive than the PX-10 and fold up for travel. For "over the head - in the ear" type headphones, the Sony MDR-W20G are the best I have tried.