Sennheiser HD 620S

The sound is the holy grail for me. They are great: lows, mids, highs are extremely well balanced (for closed back), they don't disturb, don't focus on any area in particular, nor lean towards any side - hyped or dull. Isolation is also great - these headphones would be my choice for tracking. However I'd buy some other headphones for people with bigger heads (for ex. me). I cannot imagine mixing even 2hours with them. They squize me and the pressure makes my head hurt, I loose focus. However sound-wise... they're perfect, I think people underrate them. I was comparing them with closed back headphones in similar price range: beyer DT-150, 770, sony mdr-m1, yamaha hph-mt8 - 620s is the winner. But the worst comfort.

I've been searching for a reasonably priced set of closed back headphones to be used in the bedroom and not disturb my partner late at night. I had hoped my HD 820s would be fine - perfect sound and no annoyance for her. Turned out this isn't the case - the HD 820s leak too much! I like Sennheiser's sound profile so decided to purchase the HD 620s - the mixed reviews are enough to put you off, yet they only go to show that headphones are very particular things. For me, I could not be happier! Absolutely no sound leakage and a VERY acceptable tonal profile: great across lows, mids and highs. Very comfortable with zero problems regarding clamping pressure and earpad seal - they are a perfect fit. Perhaps I'm just lucky - my head shape somehow just right - but I don't care: these are some of the best headphones I've used and I've used many over the years. Using them with ARIES II ladder dac and a Topping A90 - nothing special but good enough. Roon Labs recent headphone profiles are interesting but, to be honest, I'm happy with the sound out of the box - I find the profiles can kill speech tonality and I'm never sure the whole Harman Kardon profile is a useful thing anyway.
Sure, being closed, my ears get a little warm but not a real issue - I like the 5 series design and they feel comfortable.
Finally, build quality: too early to say but my guess is that they'll last. Good use of different plastics, along with the metal backs of the phones, would seem to make them durable enough. Earpads are replaceable, so that shouldn't be an issue.
All told - an excellent set of phones at a VERY reasonable price. Highly recommended.