So far, early impressions are not good. There seems to be a lack of clarity, especially in the lower mids. There is certainly more bass quantity than my K500, but it's not as tight - honestly, it's a little boomy at the moment. The mids are nice, but I don't think they're as engaging as my K500. The treble doesn't offend, but it lacks sparkle and energy compared the the K500 right now. They also sound a little closed in. They do sound much more open than say my Soundmagic PL30, but they don't sound nearly as open as my K500. For what it's worth, these are very early impressions. I will need time to get adjusted to the sound since the K500 has been my only good headphone for the last two months and has become my reference point for sound reproduction. I've almost always have had very negative early impressions of my favorite headphones so we'll see if the Shures grow on me like the K500, HD580, or normal bias Lambdas did.
Regarding the isolation, it's solid for a closed can. Most ambient noise and softer speaking is blocked out completely, but I don't think commuting with these will be an option. It's perfectly suitable for home listening in most cases, but my bedroom at my apartment is somehow louder than it is on the street unless I close the window which makes the temperature almost unbearable hot sometimes. I think I need to sell the Srh-840 and get some IEMs, regardless of how much I may come to like them. I originally bought them because I needed a pair of headphones with great isolation so I can listen regularly in my apartment without having to sit in a sauna. With the isolation how it is on the Shures, I don't think they'll be able to hold up to my requirements.
