Evans EMAD Resonant Black Bass Drumhead. A fast and efficient way to change your tone without changing your entire resonant head. The EMAD Resonant comes with 2 interchangeable foam rings that allow you to manipulate the bass drum resonant head sound without the need for internal damping. The 2 foam rings vary in thickness to vary the amount of overtone dampening. Each ring eliminates overtones around the edge of the 5" offset microphone port and offers varying degrees of control over attack, sustain, pitch and feel.