P'ups for a Heavily Mid-Rangey Sounding Bass

You've tried bypassing the preamp and wired the pickups direct to the jack, then use your amp for eq?

 

How does the bass sound acoustically? The mids might be in the preamp, as stated above.

If, after everything else is tried, if you still have too much mids, find a slightly underwound pickup, like a Fralin -5%, soft magnets, 250 kohm pots.

 

Sorry for the short post above- was pressed for time, and didn't know if you had tried that yet.
Basically, it just gets the eq out of the chain, and lets you know what the pickups you have can transfer to the amp- maybe the bottom you're looking for (or not). But at least you'll know what the bass with those pickups can do. If you not able to get what you're looking for straight thru the jack, then different pickups to taste.
But if the preamp is 'coloring' your tone, then you know where to start.

 

Yeah that old Dimarzio P is super mid-rangey. I had the same problem with my 80's maton (ebony/maple set neck & queensland sassafrass body). Acoustically, the bass has some strong woody mids. As these are getting a bit collectable now, I wanted to keep it all original, and I tried hard to like the Dimarzios, but after 8 or 9 gigs I had to fire up the soldering iron.

Unlike yours, the bass was passive, and the first thing I tried was to wire that P in parallel mode. This was a big improvement. The pickup worked a lot better with the (still in series) Dimarzio J. I'm surprised no one has mentioned this. It's simple and easily reversable. You should try it before you go buying new stuff for sure.

Next I added a 2-band preamp with a bit of a mid-scoop inherent in the design. This is my own design. There's nothing really like on the market, but think sadowsky or aguilar obp1 I guess, but more subtle.

The bass was really close, but not quite there. The parallel P was now too brittle in the treble, so I swapped it for a cheap ceramic mag P (wired in the standard series way) and that's pretty much it.

There's been a few more tweaks with the blend pot and the input Z of the pre. Plus it also has a double volume pot with different gangs for active and passive. I tried a few things along the way that didn't work out, but that's all part of the fun.

This tweaking has allowed me to get just the right loading on the pickups, in both active and passive modes.

This is now one of the best basses I've owned.

 

Yeah, swapping that Dimarzio P for pretty much anything else will give you less mid range for sure. It's the most middy bass pickup I've ever heard.

 

If you do replace, I would suggest checking out the Nordstrand PJ sets. I have used Np's and NJ's for replacements and they have a much different character than what you are hearing- definitely a wider response. The Nordstrand PJ set has the split J, which I haven't tried, but I imagine it would be a pleasant change. Ed Friedland has some clips of different P's on his bass whisperer channel, and the NP's are on a couple of the instruments.