This would be a compression-driver horn system using TAD drivers and Tractrix horns (the only kind of horns that don't sound like horns).
I could use some help scouting out options here. DIY is not an option...
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[The sound of the huge and incredibly expensive compression-driver horn system used in the Welborne room at RMAF, bi-amped with his amps, has captivated/haunted me since hearing it - I may want to see how close I can get to that particular sound for a fraction of the cost.]
First, I'm certainly not an expert in all things horn, but I'm not aware of any other full compression driver commercial systems - drivers that will extend down into the midbass or bass are either vintage (ie effectively DIY) or custom/boutique like cogent.
Second, with any type of horn, if DIY isn't an option, then 'low cost' pretty much goes out the window. All full-range HiFi horn systems I'm aware of are at least reasonably pricey. The Edgar Titans are 1/3 the cost of the Cogents for example, but that's still 10k. The Oris Orphean semi-kits from Bert at bd-design.nl are 'reasonabe' in that context, but they're only tractrix down to ~250 and are intended to be matched to normal reflex cabs below that. You can cut costs by looking into the pro audio world which is what I did, but you generally won't find anything but treble compression driver use - midrange and midbass/bass are cones.
Not to be entirely negative, but if you want to explore the full-range CD system, you may need to think along the lines of hooking up with someone locally that can build horns to your spec and persue a semi-DIY approach, since you are unlikely to find much off-the-shelf. Starting with something like the Oris Orphean tops with a cone-driven bass/midbass horn down to ~70 as a baseline would be pretty manageable, and would allow you to work through some aspects while mapping out the bass CD idea. (yeah, that's a 3-way but the Orphean comes with a passive xover for the coax driver, so only a 2-way active would be needed)
