Audison Prima APBMW S8-4 BMW Underseat Subwoofer Upgrade – 4OHM Version! Please note you only get ONE. Huge bass from these standard under seat positions is usual, beautifully balanced musical bass has always been much harder to achieve until now. Audison cast a magic spell on this trickiest of upgrade solutions with this superb under seat subwoofer. Physically designed to drop into the original BMW enclosure this plug and play fix for dreadful BMW bass is quick and easy for your installer to fit too. Price is for a Single Woofer. Technical Specification Size mm in. : 48 (1.89) x 18 (0.71) x 7 (0.28) Weight of one speaker kg lb. : 1.21 (2.67) Voice Coil Ø mm in.