d&b subwoofers come in all shapes and sizes: whether large or small, permanently installed or mobile, flown or ground stacked, they provide frequency extension suitable for any sound reinforcement application. Some models, including the V-SUB, Y-SUB, B4-SUB, 27S-SUB and 27A-SUB, are driven by a single amplifier channel but exhibit a cardioid dispersion pattern. They provide directivity control at low frequencies, whilst keeping the amplifier channel count low. Others, such as the B6-SUB and B22-SUB are inherently omnidirectional.