*U.S. Patent No. 3,302,748 , 02/07/1967 (app. 04/11/1963) [DjVu320KB]
LOUDSPEAKER SYSTEM (class 181/31)
Reed, Prentiss B.

Abstract: This invention relates to loudspeaker systems employing a dense gas as the acoustic coupling medium, for general use such as with radio and television receivers, phonographs and public .address and auditorium sound systems. It relates more particularly to methods and means for maintaining nearly uniform, the acoustic response characteristics of such loudspeaker systems as they undergo ambient change in temperature and barometric pressure to which normally exposed.

*U.S. Patent No. 3,329,236 , 07/04/1967 (app. 06/03/1966) [DjVu61KB]
SPEAKER ENCLOSURE (class: 181/199; 52/288.1)
Arden, David
Abstract: The present invention relates to loudspeakers and specifically to a speaker enclosure which provides wide angle  distribution of sound over a wide range of frequencies. It is a well known practice to install a loudspeaker in the corner of a room so that sound is reflected from the surfaces of the walls which form the corner. The sound is distributed evenly over a wide angle and improves the coverage of some types of speaker enclosures which tend to be somewhat directional. The speaker enclosure disclosed herein, while adapted for mounting in a .corner, has a corner baffle arrangement incorporated into its basic structure and will provide the desirable effect at any convenient location. Mounting the enclosure in a corner enhances the effect further. A wide range of frequency response, particularly bass response, is made possible by utilizing a pressure damping device, such as described in my U.S. Patent No. 3,159,719 entitled Speaker Enclosure. This damping device allows the enclosure to be small and compact, compared to other types of comparable bass response, and is particularly adaptable to the present enclosure.

*U.S. Patent No. 3,457,370 , 07/22/1969 [DjVu72KB]
Impedance Correcting Networks
Charles Paul Boner (assignee C.P. Boner and Associates)
Abstract: In a sound reinforcing system, impedence correcting networks for connection between a plurality of loud-speakers and a crossover network, whereby the loudspeakers and said correcting networks will properly load the crossover network so that its performance will be the same as if it were loaded at its design impedance.