Plywood & CNC
We don't build cabs out of 3/4" baltic birch ply because this is the 21st century and we can do it better! We use a CNC machine to cut complex interlocked crossbraced reinforced designs which put the stiffness and strength where it's needed and leave out the weight that isn't required. We have a special dual-density ply made for us, that maximises stiffness and lightness. It makes the cabs far more complex to design and more expensive to build but you end up with better tone, excellent durability and lower weight. And the extra cost is insignificant over the life of a cab - just ask anyone who's bought a Barefaced cab if it was worth it!
I could write a lot about this, and I some point I'm sure I will. But I've seen a lot of talk about woods and plywood when it comes to guitar cabs in particular and it really is so much faux science - great if we want to write a script for Spinal Tap 2, but not so great if we want to make a better cab than the usual suspects. Email me your questions and it'll inspire some responses that hopefully make sense to the musicians reading this - I suspect the engineers reading this are already on board!
Here's what a Big Twin 2 looks like without the outer panels: