This is actually the first design i ever did, 2 spl enclosures for 12" jbl gt5-12 subwoofers in 64 liters, tuned to 37hz for each enclosure, 18mm mdf used, with internal bracing and towel based dampening.
luckily i still know roughly know how the design was, so i'll attach an image of that soon on here. (not exact measurements though)
i eventually sold both subs for €100, making a loss on the value, but i had them without having a purpose for them.
Design files won't go up as i simply don't have them anymore :(