So I'm not sure the DT 990 is better than the HD 599—though they are definitely better than the 559.
So I might as well mention what they're good for and what they're not.
First of all, the DT 990 is studio headphones. They're designed to show you *all* the detail. So if you're looking for critical listening, they're great. You will get *all* the bass and the treble with an expansive soundstage.
But they also require 250Ω of power. Which means they *require* an amp. They're not useful for computers or phones unless you have an amp plugged into them.
The other thing is, because they're studio headphones, they are not forgiving. Meaning that *if* there's a flaw in the audio, you will hear it. So if you're hearing brick walled audio or clipping—and a lot of recordings nowadays are like that—they will eventually fatigue your ears.
Nevertheless, if you want to hear everything—including the ugliness—the DT 990 definitely delivers.
