I've got some semi-open and closed back headphones. Fostex t50rp, EEMU Teak, Audeze Mobius, ATH-M40x, Sennheiser HD25 1 ii, PSB M4U1/M4U8 (own both).
I had the TH900 for a bit, and loved them.
· What do you look for in a closed-back headphone?
I want the sound stage be bigger than I would expect from a closed back. I hate feeling claustrophobic in a pair of cans.
Comfort should be good, too strong of a clamp hurts to wear too long, not enough clamp means I'm constantly worried how far I tilt or bow my head while reading.
With open backs, I can forgive a bit of brightness because the sound pollution helps dilute it a bit, but with closed backs, I prefer a neutral-warm sound. PSB nailed the basic signature, but stage is tiny, imaging wasn't the best, and details weren't top notch. There was more I took issue with, but for the price, and efficiency, it was hard to dislike.
OH. I want them to be efficient! Critical! I only use closed backs when I'm out and about. VERY VERY RARELY at home. I want that sound isolation while studying at a library or something. Needs to be performing at peak off of a DAP for me.
· What kind of strap/headband do you prefer?
I enjoy the suspension systems like on the newer Hifiman, The newer Fostex t50s, and the LCD2C. I can live with well or decently padded bands, like on the EEMU or th900, or cushioned segments like on the Sennheiser HD6xx.
· Are there particular brands you like?
For closed back? Fostex is my go-to, but I love LOVE the sound on MrSpeakers Aeon Flows (open and closed). I'm waiting on the Meze's, but the ones I tried for a short period at CanJam were pretty solid, just wish I had more options than WARM. I like some warmth, but a bit more balance. The Audio Technica closed-back I have has a decent balance, but the stage isn't the greatest, and the clamp is next level (same complaint for the Senn HD25).