Update and further review:
The Crack really can't handle these 50 ohm headphones so I've switched over to the S.E.X. and compared them to my Sennheiser HD650's.
Keep in mind the Senn HD650's retail is about $500, the MrSpeaker Alpha Prime is $1000. Also the HD650's are open backed, Alpha's are sealed.
My Senn's have a Mogami cable, Furutech ends, silk sleeves - I've put some love into them. Alpha's I bought with the stock cable - no additional love added.
My last set of sealed back's were Koss Pro4 AAA's from 1980 or so - loved 'em to death until my roommate ran them with the Bose 901 active equalizer and blew them out. Koss rebuilt them but they were never the same.
Spec's on the Senn's beat the Alpha's. Senn's are 300 ohm, Alpha's 50 ohm so you have to have an amp capable of driving them.
My chain is PC based flac to Squeezebox duet, output Toslink to a Stello DA220 DAC and Mogami interconnects to a Bottlehead S.E.X amp.
and....
Alpha's win.
Senn's don't have the bottom end (in spite of the specs) that a sealed headphone can give you. Alpha's have a better sense of placement and depth. Instruments are placed very specifically and easy to pick out. HD650's don't do that for me. Things are there and in their place but not like the Alpha's. Frequency range on the Alpha's is perfect and not brittle or bloated. If you don't like what you hear they come with "doggy treats" - padcovers to bring freq's above 4k down 1db and bluemonkeydots to put directly on the transducer to adjust things even more. I've not changed these yet but so far have no reason to.
Comfort is not an issue and you can wear these for hours. The earpads are very thick and the head pad is suede and slitted for even more comfort.
My one complaint is that this stock cord is too short- 6' doesn't let me wander like my custom 14' one does. I've ordered parts and will be changing that.
