... SPL power sound subwoofer S218FEATURESThe powerful Blackline Series S218 sub-bass system has been designed to be used with large scale ... tri-amped H3 system. The S218 provides good bass punch with extended sub-bass output from two new, long-excursion, 18" ( ... triple roll surrounds.TECHNICAL SPECIFICATIONS1.Type: dual driver, vented sub bass system,2.Drivers: 2x18" (460mm) / 4" (100mm) voice coil LF ...