If you visit the above link, second pic from bottom shows the cabinet without any folding like structure inside. Also I can see that some polyfill like stuffing in third pic from top. The author did not write much about the design other than that he built them for use as desktop speakers. But it is worth noting that he is an audiophile and diyer.
The cabinet looks so lovely that I thought someone can try it with the Tymphany 3.5" driver from linuxguru. Since it is expensive solid wood, having proper dimensions in place will help.