B4 Subwooferd&b audiotechnik B4 SUB Compact Cardioid Subwoofer The B4 SUB is a high performance, actively driven cardioid subwoofer designed for precise low frequency reproduction. Featuring a 15 front firing bass reflex driver and a 12 rear firing bandpass driver, it delivers powerful, controlled bass while minimizing unwanted rear energy. Built for ground stacked setups, the B4 SUB reduces low frequency reverberation, ensuring clarity and accuracy in any