Thanks everybody for your insightful replies. I read each and every one of them.
No, I'm not trying to make my Q4 or BB70 sound like my P-bass, but thanks for turning me on to those Nordy split-coil J pups. I appreciate what my BB70 and Q4 bring to the table, it's just that it's a struggle sometimes -- most times in fact -- to get a "usuable" tone on stage -- endlessly tweaking the onboard preamps and my rig's EQ. I often bring my Carvin to gigs as a backup and also because I want to give my shoulder a break from the weight of the P-bass. I've never made it thru an entire set on the BB70 or Q4 before giving up for the P-bass.
One of you asked for me to post some sound samples. I'll get to that in the next couple of weeks. I think I'll make those DI into my recording console. I know the the bass rig makes a huge difference, but I'm guessing you'll want to hear the DI?
Others had great suggestions regarding putting my active basses (Spector Q4 and Carvin BB70) thru different bass rigs and/or EQ differently from my P-bass. For sure -- I've been discovering this since I'm blessed to have 2 different bass rigs: 200w Traynor SB112 combo amp and Mark Bass LM250 into 2 Ampeg SVT210AV cabs. The P-bass sounds great into either of these rigs, amp set flat'ish. Any, and all EQ tweaks, on the amps produce great usuable and inspiring range of stanky bass tones with the P-bass.
The Q4 and BB70 on the other hand are very mid-forward and challenging to control. I'm always pulling down the mid controls on the amps, and pushing up the bass control -- in an endless search for a nice fat bass tone that sits/cuts nicely between the kick and electric guitars. Trouble is the sub-bass rumble comes up, so I'm now using a HPF pedal before the amp so I can crank up the bass controls and chop off the rumble with the HPF. This is working great with all three of my basses...making the P-bass sound even better in fact.
On my BB70, I just changed out the old Cobalt flats (heavies) for KSB pressure wounds (mediums). Now it's a great slap machine bass. The mids are more balanced with the KSB strings, but I still need to boost up the bottom. We'll see how this sounds in my band practice this weekend.
Oh yeah -- one of you mentioned pup height -- I've gone down that road years ago. My pups, on all my basses, are as high as they can go on the edge of warbling the intonation. The Q4 and BB70 outputs are hotter than my P-bass. I've trimmed both pres as low as they can go in an effort to match my P-bass output. If I lower the pups, the volume goes down, but the tone gets thinner.