After 45 of pro career in music I would have understood that if the PUs on a simple jazz bass are the problem, I'd have already replaced them since a while mistaknowitall...Thank you for advice. After 45 years of playing professionaly I think I figured by now how to use "those knobs".
This is string section and question was about strings. Please refrain from off topic advice.
EDIT: hey I'm not gonna let you down though, just my 2 cents as it has already been discussed on another thread: "want low mids ? go barts and done"