Quote Originally Posted by GM View Post
Why waste the $$$/weight penalty? Minimally braced 19 mm BB or Apple ply is more than adequate to control dual 15"s flexing only a few mm.

GM
With all due respect......my experience is all I can pass on & that was that I had my cabs built by a professional cabinet maker who fully understands the design & construction of loudspeaker cabinets. He made them from 3/4 ply & braced the heck out of them.
All I can say is I heard a world of difference when I added the extra layer of 3/4 ply.