Bass OptimizerSpecial Note: The Bass Optimizer is only meant for our older passive cylindrical subwoofers. This is no longer necessary on our current powered subwoofers. The reason for the bass optimizer is that TN series tube subwoofers are all overdamped bass reflex systems that need special equalization for flat extended bass. They also need infrasonic filtering to keep bass frequencies they cannot handle out of them. To date, you need to get our amplifiers or