And for this, I really do mean portable and not transportable. The closed back's I currently own are the TR-X00 Ebonies and AudioQuest NightOwls and very much enjoy the sound sig on both. Issue is, they are a pain in the butt to carry around even when I have my work/travel bag as their cases just take up a good bit of room. Also, neither isolates very well and the Fostex tends to leak sound like mad.
So far, I have been thinking of the ATH M50x as it's collapsible and and seems sturdy enough to be tossed around in my bag without breaking. I've also looked at the V-Moda M100 for similar reasons. Although they don't collapse, the Sennheiser HD 569/598 Cs look to be very lightweight, sturdy, and overall not very big. I've also seen the Thinksound ON2's here for a good price but I'm a bit apprehensive to get them due to them being more on-ear than over-ear. Their sound sig does seem to be up my alley and they do appear to be rather portable.
For context, I've tried the Status Audio CB-1 in the past and did not like them. I've also tried the Meze 99 Neo's and while I enjoyed the sound, the pads were very uncomfortable and made my ears sweat like mad. The Beyerdynamic COPP's were quite comfy but didn't have the SQ to back it up (my pair had some very bad cup/driver rattle). I also returned some Aeon Flow Closed due to their sound despite them having great build quality, accessories, and comfort (SQ way too lean and cold for my taste).
Price is of no concern as long as they sound good and are truly portable. I tend to prefer cans that have swappable pads (velour vs leather) and cables (length and/or mic'd) but if the headphone is good enough then I guess those two things won't be missed. I also vastly prefer over-ear vs. on-ear.
Any and all suggestions are welcome. Many thanks.