This very unusual speaker was built by Tim, Ryan, and others as a show project for the Michigan Technological University’s Student Audio Engineering Society chapter. The year was 1997. The drivers were one of the Raven R1 tweeters, 7″ Focal hi-efficiency mid-ranges, and 12″ Focal woofers. The general construction was dipolar to save weight. Two of the mid-ranges have cloth covered foam pieces over them to control dispersion (those are the black things). The woofers are wired in parallel to counter the dipole loss in bass efficiency, but that made the impedance around 1 ohm. The baffle is a light weight balsa composite, and the yellow stuff is a spongy, “memory” foam.
This is an older 15″ EV driver mounted “backwards” in a test cabinet (actually Speaker II). While disassembling the test setup I placed the screws on the speaker without even thinking about what would happen. The magnet on this driver was so strong that it lifted up the screws along the magnet lines of force.