Thanks for that great description. The neo-soul tone is something that is really big here in my neck of the woods and it's really one of my favorite bass sounds. I find that a very large portion of the music that I am listening to (and my fellow players) have very similar bass tones. It's true that some tones are great for recording but not great live, but I find that with a groovy neo-soul type of band where everyone is familiar with the recordings and the vibe, that smooth, mellow, round bass tone is amazing and completely necessary for the music. For me, it's what gives that style its whole vibe. It's deep but never boomy, fat and round, with super smooth mids (and pretty scooped in the right place), and just a hint of treble.[/QUOTE
It is one of my favorite bass tones as well. I think compression has a HUGE amount to do with it, especially on the records. I use heavy compression on R&B and soul type stuff to smooth out the tone. To my ears it fattens up the low end considerably and keeps the low end of the tone from decaying as quickly, therefor it makes it seem like there are less highs and mids when there really aren't-its just that the compression will keep the lows in the mix longer so to speak. I have found the secret sauce for my tone, both recorded and live is my Darkglass VU, and my Empress compressor. The darkglass is a super musical 4 band eq. I use it to dial out upper mids and highs and boost low mids and lows and then the compressor adds the polish and smooth factor. I have been doing some sessions with an artist that wants a neosoul vibe to his music and he wants a tone similar to what you are describing, except I am using rounds for sustain and little more bite. I don't pretend to be an expert by any means at neosoul, but I promise that the tones you are liking on the records you mention are crafted with careful compression and equing, most likely in post production and probably taking the bass direct the board. I have yet to do a session where I get to mic a cab, everyone always wants the bass direct, but I am sure engineers will love the AK if they will give this a shot lol.