So I tried Fender original strings that came with the bass and liked them a bit. I had used D'addarios NYXLs for a while before on the Elite I sold, but I decided to look for something else. Tried DR PureBlues - too boomy with EQs set flat. Have DR Nickel Lo-Riders, D'addario NYXL and XLs in my possession. Not sure what to try next? Looking for a nice fat lows, good midrange and smooth highs. Where do you recommend I start? Thank you!
Nickel Lo-Riders. Not quite as fat and full as the RCBs, but good midrange and somewhat subdued top end. Not zingy bright.
While I don't have a MIA "Ultra Jazz" my upgraded MIM Jazz 5 is similar, with Aguilar noiseless pickups and Audere ProZ preamp. I also have a passive Squire VM70's 4 string with Aguilar noiseless pickups and have tried a few sets of strings that you've tried, namely NYXL's and Pure Blues... ... But there is one other set of DR's that I think you should try: DR Sunbeams. They are nice and crisp when new, but mellow nicely, sound really nice both passive and active. I didn't like the NYXL's on my Jazz5 at all and I thought that the Pure Blues weren't quite was I was looking for. I did a gig Friday night with my Jazz5 with Sunbeams that are a few months old and they sounded great, both live and on a streamed recording that I got to hear. You might really like the Sunbeams. FWIW the gauge I have is 45-130 on the 5 and 45-105 on the 4. How is the tone definition with those on the lower strings, particularly low B (for 5 string, of course)?
I used to play Sunbeams back in the day but used Carvin LB75. Totally different bass. I might try these as well.
Funny you should ask about the Round Core Boomer low B... No issue with either of the 4-string sets I've tried (45-100/45-105) in terms of clarity and definition. But I didn't care for the 126B on my Yamaha as it sounded a bit too "mushy" and undefined.
I have these on a passive J-bass, and they are great. Nice thump and growl, but not muddy. I also like the flexibility of DR's round-core strings generally. I love Fat Beams too, which are my favorites on my G&L SB-2, but I haven't tried them on a J-bass. I'll toss out another suggestion: Dean Markley SR2000. I have a set on my G&L M-2500, which of course isn't a four-string J-bass, but IMO they are fantastic. I think they're nicely balanced, with punch, warmth, and clarity across the strings. I recently bought a four-string set for my G&L JB, because I think they'll be great on a J. DR has been my favorite brand for years, but my M-2500 came with three sets of Dean Markleys (best case candy ever), and I've been mightily impressed with the Helix (discontinued) and these SR2000s.
+1 GHS Round Core Bass Boomers are my choice for my jazz. A BIG plus is that they use balanced construction for more even string-to-string feel; volume, and tone. Balanced Nickels for a darker overall tone.
I really like Fat Beams on J bases, including the Ultra. The highs will mellow some after breaking in.