They appear to get closer to open sound than any non-ported / semi open type "closed" headphone. There is a price for that tech and giving an extra chamber for bass, reducing resonant boom and bloom appears to make it more directional than folks are used to. Still not as open sounding as the open HD800S. I think many were hoping for that, and about the same prices. Consider this, if they made a closed HD800S that sounded as open, with similar frequency response at the same price, why would the even bother to make the HD800S, for those who do enjoy disturbing those around them or only listening alone in quiet rooms? The struggle to get at last close to as open sounding, with control of the bass, which is of course increased, with those still being closed (not heavily ported or semi-open) requires new tech which is a lot of R&D, trial and error, etc. before it hits the market. I can understand why it's costly and not easy given how hard it is to make closed sound open, they get close. I've heard some of the higher end closed Audio Technica wooden series that try to do that with chambers for the bass and other things. The result was bass rolling off way too early, and a distant sound that was artificially open. These didn't have that problem when I tried them. As far as thin high mids, I find in having more sensitive ears, a mild dip in the high mids to low highs makes them better for longer listens. What we don't hear is reviewers calling them too forward or shouty, overly sibilant and fatiguing after long use. Therein lies the trade off. Some generally like bright, some loathe it. Some have more sensitive ears in that area, some have hearing loss. Can't please em all.