Disappointingly thin-sounding

I was replacing some KOSS headphones in the same price range -- around $30. The first time I used them, I was listening to AM radio and they sounded fine. But upstairs in my office, I almost can't believe how flat and thin they sound. The first thing I did was open my equalizer to find a better setting. But it's not the equalizer, it's the 'phones. They just lack that crisp, bright, rich presence that I was hoping for.