I’m going to try not to blather on, because this is such a rabbit hole that I’ll write a novel..
But let me start with this- I had an Ibanez Mikro 5’er, which is a 28.3” scale. It had a great B string, with a cheap crummy bridge, the factory strings, the aforementioned scale length, and being a ~$200 bass new.
Now, was it a symphonic low B, both deep and tight, like my Roscoe? Not exactly, but was it a floppy, boomy mess that rattles and has no definition? NOPE, it was great! It matched the bass, and I don’t mean that the bass had a bad sound, so a bad B fit right in..
in other words, I find people sometimes want a tight Piano-like B string, but the rest of their bass isn’t tight or piano-like. They may want a deep, thunderous low b, the rest of their bass lacks all depth and thunder.
so blah blah blah, work with what the bass gives you, paired with understanding what you pull out of the instrument yourself, and what you’re trying to get out of a b string in the first place.
As far as string advice- try BOTH thinner AND thicker gauges, because it’s not always that thicker is better.
With a thicker B string that requires more tension to get up to pitch, it may be that a tighter string rattles and flops less.. BUT sometimes a thicker string rattles MORE because the extra weight gives more inertia on the rebound, so certain playing styles actually suffer from a bigger/tighter B. The other thing to consider is that, all things equal, a thicker string will have darker overtones (less harmonic content), and it can be the case that what you NEED is more overtones to define the sound and render some attack to the note.
On the flip side, a lighter string will have more harmonic content, sure, but the surprising part is that paradoxically a lighter gauge string will sometimes rattle less, because it requires less effort to pluck, so you can play with a lighter more controlled touch. BUT obviously a string with less tension can indeed flop and rattle more as most people expect..
So, obviously, not only does your personal technique and play style and genre effect how you would want to approach string choice, but the position and voicing of the pickups can also be such that you need the lighter string for more harmonic content, OR you may need the thicker string because there is too much harmonic content washing out the fundamental/low overtones, leaving it nasal or strange wolf-tone sounding.
And the last thing to touch on, but probably the first thing to think about, is what you want out of a 5 string / low string, or how you’ll use it. If what you want out of it is big fat low notes, it may inform your string choice, as well as render some basses/pickups/positions less than optimal.
Similarly, if you are maybe a jazz or chamber music kinda guy, and rather than humongous low notes, what you need is an even response and the option to play across strings for runs or play chord voicings, you may choose xyz.
Get what I’m saying? A clear understanding of your goals, how a particular base relates to it, what that base can offer to a B string in the first place, etc etc all matter.
Now for the crappy part- some basses just won’t do what you need/want.. some bases, like fenders, have a ton of R&D and tradition around the 4 string version of an instrument, and if the five isn’t afterthought, it’s not always guaranteed that it will be incredibly versatile, or even a sparkling addition to an instrument.. for a lot of people, a five string precision bass isn’t going to do what they want.. I personally like the sound in its own character, but I don’t tend to find that it’s an amazing fat sound whatsoever, just as an example. Oddly, of the basses I’ve played a lot, fenders tended to not wow me as five strings in general.. a good, five string jazz is a fantastic instrument, but like a lot of things fender, sometimes an instrument just doesn’t seem to be a ‘good one,’ and I frankly don’t have a great theory for exactly why that is, because I’ve played some well set up five string jazzes that just don’t seem to get it done, whereas when it works, a good jazz 5’er is probably top-3 instrument.
Back to the OP, I think a lot of things have to be right- you’ve got to find the strings that work for you, you’ve got to know what you want and you have to work on finding what a bass CAN offer, and whether your goals align with it.
But fundamentally, I absolutely rebuke the assertion that you must have a 35” scale or longer for a low B. It CAN help to get a CERTAIN kind of B, but it’s not a fundamental requirement, even for a tight and versatile B. I think pickup position and a good neck/design have WAY more to do with a B string’s successful integration into a playable instrument.
