I actually had the pleasure of being guided around that rig from Doug once here in Virginia. He was a friend of a good friend and we got to talking about preamps after a gig. This was right before he switched to the Egnater gear.
I've studied the hell outta that tone simply because to my ears, it is SO unique. First question to him out of the gate was how much his 4-string basses sound like his 12. He jumped all over that one and responded, "alot of people think the 12 string is on most tracks when really, it's the 4." He seemed very proud of that and should as I've never heard more crazy harmonics out of a drive rig then when I heard that one live (now 4 or 5 times over the years).
First off, there are no crossovers in that rig. He runs his split signal as I remember Entwistle running his, with 1/3rd octave eq's. I personally don't care for that method but hey we're talking Doug and The Ox and if that's what they run, fine with me !!

So one eq cuts the hell out of the highs and is mostly boosted lows, the other has most of the lows cut and then boosts between 2k and 5k of all places. I'm assuming alot of his magic (other than his attack) come from the 3-5k area. I also noticed a compressor in there which he mentioned was key for that crazy sustaining clean low-end he gets. I've heard that rig 10 ft away with just the lows and then the high-end drive kicked in. The lows made my eyes water and sustained forever.
The new Egnater preamp is giving his drive side a Marshall-esque grind, then of course to that 2nd eq for shaping.
Still trying to figure that rig out to this day just for fun. You can clearly tell his tone has decades of influence from all of his heroes. They are all piled on at once and when both sides are going strong, it's a crazy cool unique sound.
The rig changes up from tour to tour but the same basic Doug principles are there every time.