Maybe someone can give me a hint...
I love the sound of the bass in this track of a great band:
There's a vibe you get with certain vintage(y) speakers as well. The low mids are kind of loose and bloomy, instead of tight and focused like a modern cab, and there's not a lot of deep bass.
It's pretty easy to get this sound if you play a pushed tube amp through some sealed 412 guitar cabs, but you need a bunch of them to get loud. My Greenboy Dually kind of cops the bloomy low mids, but can also put out some serious lows and make your pants flap if you feed it right.