I'll start with my find yesterday:
Dayton H10RW 10" Round Waveguide 1" Threaded, Parts Express, $12
Compression driver: Selenium D220Ti
Sounds great, no colorations observed. No foams used. Feels plastic but strong.
Is that your actual measurement of the Selenium D220Ti in said waveguide?
If so, that's actually pretty good vs some of the curves I have looked at !!