The Celestion TF1230S is the best performing drop-in replacement 12 inch woofer for the Mackie SRM450 Mk.2/Mk.3 sound reinforcement PA cabinet. It's easy to repair your broken SRM450, simply disconnect the old, burnt out or broken woofer, drop in the TF1230S replacement driver, reconnect and you're good to go. It's as simple as that! Nominal diameter: 305mm/12in; AES power rating: 300Wrms; continuous power rating: 600W; EIA power rating: 450W: nominal impedance 8Ω; sensitivity: 96dB; frequency range: 50-4000Hz; voice coil diameter: 75mm/3in; chassis type: pressed steel; magnet type: ferrite; magnet weight: 1.7kg/60oz; coil material: edge wound copper clad aluminum; former material: polyimide; cone material: Kevlar loaded paper; surround material: cloth-sealed; suspension: single; Xmax: 54.5mm/0.18in; overall diameter: 317.5mm/12.5in; overall depth137mm/5.43in; cut-out diameter283mm/11.14in; mounting slot dimensions13 x 6.6mm/0.51 x 0.26in; number of mounting slots: 8; mounting PCD range: 299mm/11.77in.