[aufeuer]

I tried removing the thin piece of foam pad that's sandwiched between the drivers and the donut circumaural pads, and that seemed to bring out the highs and tighten the bass. I haven't heard the k501 which is known to lean towards the top end, but I think this mod brings the K601 closer to Grado territory. Has anyone tried this before?

Those who find the K601 to be slightly dark might want to try this out.

 

[dty]

I just tried this with my akg k701s. It sounds a little cleaner...barely noticeable though.

 

[aufeuer]

I'm still trying to decide whether this makes the highs a little less smooth though.