Ohh cool that’s a new hobby unlocked. Could a DIY speaker really sound as good as a high end speaker?

Virtually all of it is about the spatial volume and stiffness of the cabinet material & design. The actual type of material, dimensions and surface finish are almost entirely irrelevant to performance. MDF is dirt cheap and highly performant.

I've built a ~700 liter subwoofer using 24" diameter Sonotube concrete forum material ($200-300 right now). The circular shape means that the only unbalanced forces occur at the ends of the tube. Fortunately, this is also where you put the driver (bottom) and the port (top) along with reinforcing material. You can make incredibly deep & powerful LFE cabinetry without even breaking 200lbs of total weight. Mine would go flat to 13Hz and could easily be moved by 1 person.