Maybe this will help:
https://www.decware.com/cgi-bin/yabb2/YaBB.pl?num=1186391559#22

Do some research!
B.

I posted the half WO in the two halves post. I think the loss of space in the closed chamber due to the modification is negligible. I am working on a drawing with dimensions on it, having no CAD software makes the task rather difficult. The empty space made by the one angled board on the right of the drawing should be filled with something such as expanding foam or firmly fastened with several braces to the outside wall. The completed speaker should have the outside dimensions of 24" x 24" x 13.5".

I'm confused by your drawing......in my drawing the final outside dimensions are 609.6mm square by 342.9 mm tall. In order to scale it for a 8" these dimensions need to be multiplied by .8 thus making them 487.68mm square by 274.32 mm tall. Hopefully this weekend I'll get a little time to make a drawing with dimensions in inches and mm.