I just did a new cable for my hd650. Not that I wanna upgrade the sound, I just wanted a four meter long cable with a single xlr connector to use with my lf339. The braiding was a real beach it took me like two hours just for the braiding and the cardas connector are so little it was close to impossible to do the job. In the end I succeeded and secured it with epoxy... came out prettyso after all that trouble and sound is like my beloved hd650, now the length is perfect for my couch! And no more Jack shorting thanks to the xlr! Four round braiding in this length is such a hassle though..
Try an 8-strand braid next time
One thing I tried once for braiding long lengths was to do it hanging the wires down my stairs. I originally tried it with the wires hooked up over a railing and the strands pointing straight down, but there was just too much wobble (though I suppose some tape along the stairwell wall would solve that). Laying it down the steps was a bit better for that, though the strands didn't untangle as nicely as when they were free hanging.