Josh - I'm also a big kid.......I can't believe I didn't see that myself!
Well waveguide V1 was a failure. It went better than expected, but I didn't think I was gonna nail it on the first shot. I designed my fixture to use a 3.375" mouth round over. I couldn't get it to curve nicely around the mouth, so I went to a 2.5" dia piece of foam. At the time I wasn't thinking that the mouth sets the geometry of the wg, so when I went with a smaller dia round over it threw everything off. As a result I have a sharp change of angle about 1.5" from the throat in the vertical.........diffraction horn!!!
That, and the Pam I used on the plug as a release agent didn't work worth a $#@t. However, the duct tape and Pam I used on the round over released quite well. Other than my throat plug being bonded to the waveguide, it looks really nice. The walls are super smooth. Once I get the bugs worked out I should be able to 'glass the back side of the wg to reinforce it, add my CD mounting plate and be ready to rock.
I'm gonna go after V2 today. I think now I can make the larger round over work, and I'm going to make a new throat plug that will allow the wall angle to be set entirely by the mouth geometry. Hopefully by the end of the day I'll have a good one.
IF this works out, I might try to build a cardioid enclosure for the TD15m I'll be using for a mid to get constant directivity down to 300hz or so, then I'll roll in my other sealed TD around 2-300 hz to bring up the falling response of my cardioid mid......but first I need good waveguides!