Have owned the 280 for about six or seven years. I want to give a brief classical music perspective on them. Known for being neutral, the 280 sounds light and crisp to my ears. The highs are bright but also very smooth. Very smooth massed strings. Brass instruments, triangle, and harpsichord all sparkle. Just beautiful highs on these and an all-around bright sound. The bass is punchy but not boomy in the least.
These headphones are very revealing of bad recordings and of low-res music. Sometimes you will want to blame the cans when it's actually the recording that sounds terrible on them. Poorly recorded strings will screech and be unbearable. If you stream your music, you're going to want to choose Tidal since they offer high definition streaming. Otherwise, I would not bother with these headphones.
One peculiarity about the 280 is that, especially in orchestral music, the instruments and indeed the whole orchestra sound slightly miniaturized. I especially noticed it coming from my HD 650 one day. Everything on the 280 sounded great, but smaller.
Now there are two things I don't like about the 280: 1) they clamp hard and 2) the long, coiled cable is really heavy and often gets in the way. These are not headphones you're going to want to walk around with. They're designed as work phones (which is why it's called the HD 280 *pro*). Under normal conditions, the cable is way too heavy for an iPod or smartphone. I have to stick my phone (as well as the bulk of the cable) in an open drawer. That way, my android won't come crashing down off my desk after having been pulled down by the 280's massive cable. On the positive side, the 280 doesn't need amping, so it sounds great just plugged into the phone.
To end with, let me say that my HD650, which looked so solidly built and which is so much more expensive, gave out in under two years with the driver on one side cutting out. Meanwhile, the 280 has taken several lickings, and it just keeps on ticking so many years later. Very sturdy headphones.
ADDED FEB 23: The Sennheiser 280 sounds best in my opinion when you're not even wearing them and just hear them as shelf speakers. Suddenly the music sounds bigger.
