High frequency driver for these Mackie loudspeakers: Thump15 Thump15A Thump12 Thump12A Thump12BST Thump15BST SRM450v3 SRM350v3 Note These tweeters can safley replace the older 4 ohm versions. Some older TH15A cabinets use a screw in type of driver that is no longer sold. Please check your driver before ordering.