When I was around 20, I started a small side business building custom speaker boxes for car audio for competitions. I mostly did work for friends and got paid in beer more often than money but it was fun and I learned a lot. I was obsessive about making good boxes so I read just about everything I could get my hands on to design the highest quality boxes. A box has to have a specific volume in order to sound right, think of a bass speaker as drum and the box tunes the drum. I don’t have any pictures of the boxes I built back then but a few of them won some ribbons.
About a year before I moved to CO I bought a 1994 Toyota Pick Up, regular cab, 4X4 with a 4 cylinder. Great little truck but it could only go about 25 mph up any hill and there was almost no room behind the seat for a speaker. I picked up two 8” Lancer subs somewhere and built a custom box that allowed me to still move the seat all the way back, I’m 6’3” and mostly legs so I didn’t want to lose any leg room. To make the box smaller I used the truck as the back of the box but lined it with dynomat to keep it from vibrating. I always intended to fiberglass the inside of the box but never got around to it. I made custom speaker grills on the CNC Turret Punch we had at the shop in LA.
For a later system I drew and cut this speaker grill but never finished the system. I was fixing up a 79 GMC Sierra short box but sold the truck to buy my trailer before I ever finished it.
I wish I had pictures of some the custom boxes I did back in the day but that was over 20 years ago now. I also built a custom box for the 98 Tacoma that went behind the driver seat and took up very little room. The Tacoma was an extra cab but I still wanted a small incognito box. I searched for pictures of that box and couldn’t find any. Kind of bummed.