Alpine SWT-12S4 12" Subwoofer Sub Car Bass Tube Box 1000w peak Focus Mk3 RS Sound to tweeters may be

Sound to tweeters may be lost

However due to the large Transit PCD  the Transit Factory studs you may not need to do this

- Mounting Hole Diameter - 5 1/2" (140 mm)

Chassis type -1U

So you MUST have the original grilles

Alpine SWT-12S4 12" Subwoofer Sub Car Bass Tube Box 1000w peak Focus Mk3 RS Sound to tweeters may beALPINE SWT 12S4 12" bass tube With 1000W peak power handling, this ready to use bass reflex subwoofer tube is just the thing for big bass fans. A protective grille ensures that nothing sliding around in the trunk damages the woofer. Speaker System: Bass Reflex Type 12" (30cm) High Performance Subwoofer Peak Power: 1000W RMS Power: 300W Overall Dimensions 324 x 660 mm Frequency Response 28 200Hz Speaker Impedance: 4 ? Sensitivity: 92dB W (1m) Stitched