I have a thread about the HD598 cable. http://www.head-fi.org/t/705465/sennheiser-hd598-custom-cable-tutorial-with-hd598-stock-connector-wiring-table
Here is the wiring table for the Stock HD598 connector for those who do not wish to follow this tutorial.
Black and Blue are both Ground, Bottom Conductors. Fuse them together
Red is Ring, Second to top conductor
White is Top Conductor,Tip
I would double check this with a continuity tester just in case Sennheiser changed the wire colors on you. I explain this process at the end of this post.
Hope this helps!
Edited by pulchritudejim - 2/13/14 at 11:36am