This is quite surprising but perhaps reflects, once again, the variance and interactions among basses, players, and strings. Still, not to find much difference between EP weichs and Obligatos is baffling. Are you talking about pizz., arco, or both? I'm curious, what is your style of pizz. play? Do you pull the strings with a bunch of the "meat" of your finger or do you have a very light touch? If the latter, the lack of a substantial difference may make sense. Not being critical-- just trying to understand your experience. Are you using these on your '64 Kay?