Pros: Mostly neutral tonality, quality timber meets or exceeds expectations for the price, good presence across the spectrum, great all-rounders
Cons: Sennheiser veil, bass can bleed a little and doesn't go all the way down, mids not always as forward as I would like ideally
My chain: Lossless -> Foobar 2k -> HifimeDIY Sabre DAC -> E11
The HD558 are doing it for me right now. I was not blown away, but they really don't do anything wrong. The bass is not boomy but does bleed a tad, not ideal for classical but it's not hugely problematic.
The mids are nice. Never overly resonant, just enough bite to give realism but not intrusive. Imaging is very nice, but transients are a little weak.
Having started my hifi game at IEMs and gone far enough to see the kind of soundstage they are capable of (TF10, SM3), and opting for my first real can to be closed yet with a good stage (DT770), I feel like I can really discern the elements of sound presentation that are unique to open headphones, and they are well-present in the 558s. The sound is not necessarily much "bigger" than my DT770 in terms of the size of the stage or how far away certain sounds are; the DT770 actually wins out on this in some cases, especially with certain types of electronic music (psytrance in particular). However the benefit of the open sound is literally the dimensionality of the sound: the individual "sounds" themselves actually have distinct dimensionality and spacial presence of their own, rather than simply being placed at relative distances to each other. It improves the actual realism of the sound and makes it sound more speaker-like or even "live" sounding.
Timbre and decay are both superior to any phones I have owned; the warmth is obvious, and I can hear the "Sennheiser veil," but it doesn't really interfere with detail or realism when you listen closely. It is more noticeable with some music than others; it makes violins and pianos sound a bit veiled, meaning these are not the BEST cans for classical, but they are VERY far from the worst; again better than anything else I own.
I will say that I personally I wish I had thrown in the extra $80 and gone with the HD598; I would like a little more upper midrange presence out of these guys, and the bass could be tighter. However that doesn't detract from the fact that these are definitely quality cans, they make a great compliment to my DT770 for when I want a more laid-back listen. Overall the sound is laid back yet involving, almost seductive; it doesn't have tons of punch in the bass, so some electronic like Justice or other dubsteppy-like stuff is underwhelming (my DT770s are better suited there) but more intricate, atmospheric stuff like psychill, Lindsey Sterling, later Simon Posford stuff (Shpongle, Younger Brother) is very involving. Even deeper house like Deadmau5 and Jackbeats is good. It can't quite keep up with some of the faster, super-intricate Shpongle tracks (I found the album Nothing Lasts...but Nothing is Lost more problematic than the rest), but then the only thing I've yet heard that can is the SM3, which handled anything I ever threw at it.
Overall I am happy with my purchase, these make a great compliment to my LEs; now to complete my mid-fi conquest I am going after something fast and aggressive with tight, extended bass, maybe a Grado? Perhaps HD25-i-II...any recommendations? ^_^