I think those K501's have stock pads with tape around them.  Just a guess. 

Went to a local head-fi meet today and for giggles showed a few people my KSC75s with headband mod. Wowed every single last one of them. For a second or two, these made them reconsider their decisions to drop all those Gs on the summit-fi stuff  .

Isn't it also titanium coated and lifetime warranty?!?!?!??!

Might as well share these...

The last one overlays the FR of another set I have.

Seems pretty well matched. I really like these for the price and for exercise. They are fun, but not DT990 fun. Gradoesque sound at a fraction of the price.

Here is a mod I did of the very poor KOSS PRO4AAAT. It really sounded dreadful stock, so I went ahead and removed the original drivers altogether and transplanted some KOSS UR40 drivers into the enclosures. As far as I know, the UR40 uses the exact same titanium drivers as the KSC75. Furthermore, I added some real leather padding to the headband that I scavenged from one of the broken vintage headphones that I had in the attic and attached some eBay Superlux HD668B velour pads instead of the terrible vinyl pads that came stock with this headphone. I used the UR40 drivers with this headphone for a while but then, when I got one of those Anniversary Edition PortaPros, I used those drivers instead as they are a bit darker and lack that titanium metallic tonality that the UR40 seems to have. The end result has really nice soundstage and great bass, although there is some ringing that I can detect in the upper mids. I think I'll solve this by adding some additional damping to the inside of the enclosure, as it is a semi-open design.

I just ordered the KSC75.

If the first pair is good enough to wow me I will buy a second pair. They are 30 Euros in the Netherlands.