The SP4 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 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 the optional cooling systems, there is plenty of thermal capacity in the SP4. Two high grade magnets provide the Gauss while 5 Fi designed 10" 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 2012 SP4 Series is designed for monster daily driving systems requiring high linearity and extreme power handling. The SP4 Series raises the bar for the industry...again.
Showing reviews 1-10 of 22 | Next
Posted by seth on 20th Nov 2013
I recently upgraded from a BL 15 to a sp4 15, and the difference between the two is crazy. The sp4 destroys the lows and in my 30hz tuned box plays down to 18-20hz. By far the bet sub I've ever purchased. If you want one nasty 15 the sp4 is it.
Posted by Joe on 2nd Nov 2013
This Is hands down the best sub I've ever heard and I'm only breaking it in with 1700
Posted by Unknown on 9th Oct 2013
Have 4 15" sp4s on two AQ 3500.1d amps and it just gets down right nasty I love it best subs for the money for sure!
Posted by Unknown on 19th Jul 2013
Has anyone else here had an issue with the surround of the drive unit covering the screw holes? So the holes where you screw this driver to your sub box you would be screwing through the surround? The surround of my speaker is covering the metal basket speaker holes so I am having to screw into the surround of the speaker to attach this unit to my sub box is that normal?
Posted by gt58 on 3rd Jul 2013
this thing gets nasty on 1500 watts rms. i couldnt even imagine 3k lol!!! im tuned to 28hz and the whole car flexes crazy. no doubt worth the wait. get it. seriously..
Posted by Kyle on 6th Jun 2013
Purchased 4 -15's. Fully loaded. CF cap.
Dc 10k @ .5 ohms.
These are the best drivers ive ever had. I wont run anything but Fi again.
Posted by chris on 30th May 2013
I just got 2 of these monsters today and there in a ported box tuned to 43 hertz with a kicker warhorse pushing them. It did take a really long time to get them but most of that was due to parts availability but they pound
Posted by Unknown on 17th May 2013
It took a super long time to get my 2 15 sp4's but when I got i was more than happy I haven't install them yet but they have a quality feel to them
Posted by Deaf by Dishonor on 12th May 2013
This is my 2nd sp4 15", and let me tell Ya. These THINGS pound. Have previously own ALL kind of subs, but my personal favorite was the 04'/05' RE XXX's, until I got these "Trunk Molesters" These astronomical subs are so precise, and acturate with their linearity, and flat responce it just bring me back to the good old days of the xxx's. High performance linear subwoofer is what you need, then look no further!!!! Tears every part of my car apart with just a measly 4000 watts, & the subs just laugh, as they are tickled to death.....not even close to breaking then in....smh...I know I'm Waaaayyyy over doing it with 2 of these steroids of a sub, but Hey-what can i say.. :-D
Posted by derik posey on 26th Apr 2013
other then having to wait a month longer then expected and not getting stickers like promised i am more than satisfied with the product. even on only 1500w rms it gets way louder then i ever imagined. great product from a great company
Showing reviews 1-10 of 22 | Next