Disconnect all wires from the busted JBL JRX112M speaker.
Inspect the woofer for tears or cracks or deterioration in the rubber that surrounds the speaker. These are the most usual sources of performance problems. Buy a surround repair kit and follow the instructions to replace the surround.
Listen for a distinct lack of highs. Overall sound is muddied or muffled when the tweeter is blown or inoperative. Replacing the tweeter is the quickest and easiest repair route. eBay is a tremendous resource for JBL tweeters, which have a part number of 2412H-1. The tweeter, because of its small size, is removed by unscrewing the screws that hold it to the cabinet and disconnecting its connecting wires from the crossover once the tweeter is out of the cabinet. Reverse this process to install a new or replacement tweeter.
Repair a woofer tear or hole. Measure the length of the tear with a tape measure or ruler. Cut a piece of black construction paper that matches the weight of the cone using a scissors. Apply a thin layer of rubber cement to the tear directly with a small paintbrush. Place the black paper strip over the tear, then press and hold it in place for two minutes. Apply another thin coat of rubber cement over the surface of the paper and let it set for another two minutes. Turn the woofer over. Apply a thin film of rubber cement using a small paintbrush. This seals the tear on the back and front of the cone. Let it dry for five hours before testing the speaker performance.