Note the five dots in the middle of the K 241 driver, missing from the K 140. Fitz posted pics of Sextett drivers here: http://www.head-fi.org/t/202122/the-headphone-driver-pics-thread/60#post_3883163. Try to look for the five dots on those.
You can't see them but the K140W has 3 dots: I took quite a few photos, but they just wouldn't show up.
Also on the backs the K140W has the #2 imprinted, and the K241 #3.
Also it's worth mentioning that the K140 W's voice coil is an orange copper. My K241 and K141 both have red copper.
Incidentally the reason I could take these photos is that I replaced the K241 drivers with K140 drivers as I couldn't find a replacement for the faulty one. (kind of an experiment)
The sound is surprisingly similar. The main difference is the K140W is about 5dB less sensitive, the bass rolls off a little earlier with a little less slam and the treble isn't as piercing as the K241 can be.
Altogether when amped properly it actually sounds excellent (almost the same) , but through my PA2V2, there is a bigger noticeable degradation in quality and extension especially in the bass.
But for a home-only headphone it's really quite good.
Edited by GREQ - 10/2/12 at 7:56am