Patents for Protection, page-6

Thanks RVR. That makes it clearer for me. With AKP's device, they appear to have patented well over 100 aspects of the speaker and many of those may indeed relate to the production methods.

Having tried to absorb some of the document in the link from caredes, I am inclined to the view that it is a work of scholarship that is worthy of almost as much acclaim as the device itself. If any stone has been left unturned I would be most surprised.