Pros: Laid back, Completely Non Fatiguing (for me)
Cons: A bit too polite. Small sound-stage
These are not the value they once were, but if you can find them for $50 they are un-beatable. For the price they go for these days the 518 is generally seen as better in every way than these. I use these for mostly rock, some jazz, techno and metal. Those genre descriptions are almost vague enough to describe my music library.
Very Good, I prefer the Velor material used on pricier HP's but the cloth used is very comfortable. After about 3 hour they start to get slightly uncomfortable because of the fairly tight clamping pressure. I remember thinking they were tight when I bought them but I put them on my 4" monitor speakers overnight and it fixed them for me.
Durability is very good, I have used these for years and they seem to be holding up quite admirably. The cushioning appears to be nearly as good as when I bought them. The plastic design may feel flimsy in hand but no cracks or noticeable stress has occurred. I thought I blew out the right driver because I accidentally cranked them to unbelievable volume one morning trying to figure out why my desk speakers sounded so weird, turns out the 515's were just screaming away, fully audible to me and the other person watching the video but have come out unscathed.
4/5 for plastics used.
This is going to be difficult. They are polite. Bass is reasonably tight has a bit of punch. To me it could go down just a bit farther, they roll of at about 50Hz. The highs are recessed but present though not spectacular. Mids and vocals are very clear, not the most brilliant sounding but in the $50 range they are unreal. Timber in the mid bass to mid range is very good, these. If you want to jam to a Cello these phones are for you. Sound stage is good, it can get slightly confused in some rock tracks, especially very fast ones. They aren't boring, but are warm and a maybe a bit slow.
I find them to be fairly accurate and will not forgive a bad recording of anything. They sort of tip-toe around the sound as if they might offend you if they are too exciting.
Value, This is the can of worms. Once available for $50 before discontinued. If you can get a used set for $50 do it. If you can't, I would skip these and pick up the 518 for about the same price as these currently sell for.
Not a "must have" headphone but next to the HD 580 they are probably the most under rated Sennheiser ever. I find they even sound like a cheaper HD 580 but without a hard of punching bass.