This is due to a lack of power. You need an amp, it will make them louder and a lot better sounding. Whenever I use any if my headphones directly into my computer, they lose a lot of bass, lose detail, and lose soundstage. Getting an amp will also make the DT990 sound better.
AntOk463
Are you looking for a friend or looking for a kidney?
I think you should get that checked out. If it is audio related only, see an audio doctor. I personally recomend Dr. Dre, but you can go see anyone.
Just put the sticker on your ears instead.
Hifi isn't what you own, it's a state of mind. If you think your setup, music preferences, and opinions are better than everyone else, then you have achieved hifi.
The amp has a hi res sticker on it, but the headphones and cable don't. So the amp is hifi but the headphones and cable is not. A few wireless headphones have a hi res logo on them, so they do exist.
This shouldn't be careful if you have kids, but instead careful if you have others around your house. Once I opened my AKG headphones and showed my uncle, and he wanted to push the diaphragm in. I'm sure he was just playing around, but I had to physically pull it away from his hand.
Even cheaper and less powerful amps can sufficiently power a surprising amount of headphones.
Can sitting in a plain cause hearing damage? I think many people regularly experience louder environments than the ambient sound of a plane.