The ROCK-on subwoofer, Granite-10D, brings bass to your outdoor space, something that is greatly needed in today’s rock speaker market. The Granite-10D features high power crossovers that reduce distortions and deliver pure sound that blends in with nature. This dual voice coil subwoofer boasts an “S” shaped port so water cannot get trapped inside. We have tested and retested our subwoofer to ensure it is up to par with our reputable line of subs.