This box used two 4x8 sheets of 3/4” arruco ply from Home Depot. About $100.
Cut one sheet into the four sides then the other sheet for the top, bottom, port, and bracing.
I’m still using this sub, which is saying something considering how many I’ve tried.
Crazy thing is, I have not seen the red light on the inuke yet. Even when I think i’m really pushing it, I’m still only seeing the third light flicker. But I don’t watch many movies in this room so it rarely gets the 20hz content. For music it’s silly inside a normal sized house.