So , I have been searching for info on DIY ISO cab and looking at the one Randall makes. I didn’t realize until looking at the posts they are boxy sounding if you make it square so the sound wave theory makes things complicated. I don’t want a giant box. I was looking at about the size of my 2 x 12 cab but it has to be about 18 x 18 to allow for the insulation. I have 3/4 birch left over from another project. I am thinking I might just build a 1 x 12 oversized cab.