[suburbanite]

Of all places, I was looking here and a Sennheiser rep said... well, see the link.
 
IMO Sennheiser should've offered this right from the beginning given that the HD 5x8 series comes with a twist-and-pull detachable cable.
 
A 4' cable with a 3.5mm jack is something Bose got right with its AE2's and OE2's a long time ago. What took Senny so long?
 
Next, we need to see 10'/6.3mm and 4'/3.5mm straight cables for the HD 380. And velour ear pads, damn it!

 

[suburbanite]

I'm told by Sennheiser that the HD 5X8 velour earpads will fit the HD 380's but am warned those pads will "affect the acoustics." FYI.
 
I'm also told that Sennheiser makes no straight cable for the HD 380, nor does Sennheiser know of an aftermarket cable that fits.