I have a pair of Sennheiser HD202s which are quite dark. I would almost say dull. But you could give them a try. They are not HD in my opinion though. I wouldn't mix with them. But they are good for tracking. If i track vocals with them i always add some high shelving EQ, cos otherwise the sound is too dark for me.
Might give them a try. But i sugest you try them out first. They hurt my ears a bit, especially after say 30min. If you have small ears i think they will fit well.
I guess there's alot of questions regarding headphones, but I'll give it a try anyways.
I'm a bass-player, having some trouble with high frequencies (because my ears aren't like they used to be), so I'm searching for mellow headphones, with good isolation.
When I think of mellow cans... I think of the AKG K240s. They are not good for isolation but you may want to give them a try. I would also use the word gentle to describe them. Gentle as in easy to wear for extended periods.