Assuming 40 x 12.5 x 22.5 are internal dimension....
Gross volume: 6.5
After displacement: 5.5 or so
32hz = 18.5
35hz = 13.75
37hz = 11.75
40hz = 9.0
I guestimated the port displacement variance among the port legnths. It's close enough
By the way, what program did you use to render that image? I need a easy to use, free program....I tried google sketch, but was way to complicated.