hum in the mix like that ... I really don,t know but I think that sound can be done with round wound ... turn off the treble on the bass preamp and on the amp and mabye using a EQ pedal to be shure to cut in the treble departement
I've met Kool twice, and I've asked him what gear he uses, because I like his sound a lot. He's tooling around with a Zon Sonus bass now, but his string choice has always been Rotosound swingbass.