The SP4 v2 Series is the latest in the progression of Fi subwoofers geared towards thundering daily drivers. Starting with a monster 4″ voicecoil for increase thermal capacity, we built the rest of the sub around that. With a proprietary US made steel water jet and machined in house on one of our CNC machines, there is no shortage of motor force in the FEA derived design. With a solid pole and open motor geometry, there is plenty of thermal capacity in the SP4. A single 10″ high grade magnet provides the Gauss while 4 Fi designed 10″ heavy progressive spiders keep things under mechanical control. Utilizing a special 144 tinsel count leadwire there are no losses with power transfer to the coil. The 2017 SP4 v2 Series is designed for monster daily driving systems requiring high linearity and extreme power handling. The SP4 v2 Series raises the bar for the industry…again.