This question differs from similar questions about wood warping because I'm not asking how to straighten a warped board nor how to fix an existing design that warped. Rather I'm asking how do you design at the outset for a large enclosure to come together square and true even if the boards and panels you have available are not straight or flat. I'm also wanting to know if there is an order of assembly that will maximize accuracy or minimize how much correcting force is needed. For instance, one strategy might be to lay the largest side flat and build up on it. An alternate strategy might be to start with a section of the innermost bracing that I can make square and true (using the best pieces I have) and build out from that seed.
This is for a large speaker enclosure approximately 2' wide, 3' deep, and 5' tall, but I think the question could apply to any piece of similar size and construction. The materials I have are 7/16" OSB panels and 2" x 3" douglas fir studs.
(A more usual choice for speaker enclosures would be 3/4" MDF for panels and bracing, but if I can build it with OSB it will save a lot on material cost. Moreover the size of the speakers is such that you can't get enough stiffness by just using thicker panels; either panel material will still need bracing every 8" or so. Rest assured I am still using MDF for the actual panel the speaker drivers bolt to, but due to the type of speaker design these MDF panels will be internal walls, not external. (These internal MDF panels form the "inner box" I was talking about that I can make most accurate in size/shape.))
I'm planning to rip some of the 2x3's to make 1.5"x1.25" battens. I know that if I take two panels that do not lay flat, and join them at 90 degrees with a batten, the joined edge will be straight assuming the panels were cut straight. I also know that a 2x3 that is warped over a long length is "less" warped if cut into short sections. So perhaps breaking the battens into sections is a good idea? However in any case, when building from the skin to the inside, I think there is still the possibility that panels fixed in 2 dimensions will have warping in the 3rd unfixed dimension? (E.g. they might bow in or balloon out even though the edges meet.)
The way I've most seen recommended online is build a skeleton or matrix and attach panels to it. In this method, keeping the 2x3's in long sections would ease construction and assembly, but I'd be worried about getting to the end and discovering an irreconcilable difference in shape between the skeleton and the skin. Not to mention differences in expansion, and resonance in the long boards.
I also thought about making a large number of "pre-fab" pieces to use to assemble the enclosure like Lego bricks. These would be C-shaped and rectangle-shaped biscuit joined studs with OSB triangles nailed and glued on top of the corners. I am not sure, however, whether these would take too long to construct, and also worry about building them to a designed size and finding out the actual size needed is different during assembly.
So, to recap: how do I make a straight object out of wood that is not straight? Should I start assembly with the longest edges / largest panels or smaller parts first? Is it better to break the design up into an assemblage of short pieces joined together, or to frame it with some of the straightest studs to make a basis for the shape?