Box for in wall speakers

[Soggy Thud]

I received 3 of the WA-8 in-wall speakers and I want to make a sealed box for them because I cant put them in the walls, but I don't know what size to make the box's. Does anyone have any estimate on how big I should make the box's?

 

[PRR]

Advertised woofer diameter, times 1.1, then cubed.

 

[Soggy Thud]

Thanks.