The Bottom Line: Don't bother buying these headphones. They are a waste of money. Go for a higher-end pair of headphones.
I bought these headphones a year ago and I am very disappointed. On a low volume they sound great. The music is very clear and pleasant sounding. If I turn them up loud they lose their quality. The reason they lose their quality is because the bass does not work properly. Bass should have a booming sound to it but instead it just vibrates. Koss advertises these headphones as having deep bass. This is not true at all! The only way these headphones even work is if you turn the bass down on your stereo equalizer. Even with the bass turned down they still vibrate on a high volume. I don't even mean mega loud. I just mean less than half way. Not even loud enough to cause any ringing in my ears and I have sensitive ears!
The good thing about these headphones is they are very comfortable because the earcups are large so that they fit around your ears instead of on top. Another cool thing is that they come with a lifetime warranty! The only catch is you have to pay for shipping to Koss and pay for shipping them back home.
If you want a good pair of headphones I recommend buying the HD-600 made by Sennheiser. Those headphones are much more expensive and require a headphone amp but are well worth the money if you demand good quality.