The Roc uses two 12 inch paper-diaphragm drivers, mounted face to face and electrically out-of-phase with one another, so that they move in concert. Remove the front panel grill and all you will see is the massive magnet structure of one of the drivers (it faces into the cabinet). There are three identical ports in the front panel, each one is 2.5 inches in diameter and segemented into quarters by vanes.