Pickups for my rr1 which is poplar body.

[kc7txm]

I also found it's not the treble thats harsh on the JB it's the high mid frequencies that seem to border on the harsh/piercing...

I've noticed this too on some guitars, I think it has more to do with the wood and size of the body than anything else with the JB. 2nd order and 4th order harmonics in the middle of the fret board is where it's the harshest on my DKMG (E4-E5, so the fundamental frequency without harmonics starts at 330-660 Hz) but it wasn't harsh until really high on my RR24 (A5-E6, 932-1319 Hz). Wood and body style (as well as bolt on vs. neck thru) plays a lot more on harmonics / how a guitar sounds with the JB than I think people give good notation to.