What did you ever decide about the tweeter? And can you spill more information about the cabinets (size, plywood or veneer, etc) and the cabinet guy? I'd be quite interested to do a tower version for a friend.
The cabinets are the same size as the part's express .56 cubic feet cabinets, so 8" wide, 11" deep and 16" tall. 3/4" ply with one big brace. I'm using bituminous damping, mostly as an experiment, and it does make the cabinet sound duller. I can send you drawings if you wish.
The tweeter is attached to the waveguide by means of a 3d printed adapter which replaces the existing faceplate and makes a smooth transition from the WG to the dome.
See post #94 on for my tests:
http://techtalk.parts-express.com/forum/tech-talk-forum/1396240-rst28f-in-a-visaton-waveguide/page7
This is the STL file.
https://www.dropbox.com/s/07l7k8wjnz6cipr/rst28f v1.stl?dl=0
You can get this printed for about 15 dollars apiece at
https://print.all3dp.com/
I'm leaning towards the RST28f, but they are out of stock for the moment. When I can get them again I'll remeasure and finish the design.
The cabinets were made for me by Leland at speakerhardware. They're baltic birch and pretty good quality. but not furniture grade. After a lot of careful finishing mine look nice enough.
You could buy the PE .56 cubic foot cabinet, or the 1.3cu ft. cabinet and have just the baffles cut. If I made this a floorstander I'd lean towards a 2.5 way configuration but that's a more complex crossover. I'm porting mine, but you might be able to use the same PR that our friends here do. I'll probably stuff the ports and run them sealed since I have two big subs in my room.
The beauty of the waveguide two way is that due to the matched directivity between drivers around Fc, crossover slope and point matter less - the tweeter's low end is boosted and distortion falls dramatically, so you can use the tweeter lower if you desire, or you can raise the Fc if you see fit. Low crossover slopes, which can be helpful blending different sized drivers, can be used, but are not necessary, so you can do an LR4 and it will still be smooth off axis.
This is very much a DIY effort, and I haven't really designed the speaker yet since the tweeter is not available right now. However, it should be pretty nice when it's done, and from the measurements I've taken, crossover should be fairly easy.