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 280 tinsel count leadwire with FOAD lead attachment ensures that there are no losses with power transfer to the coil. The upgraded 2014 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 51 | Next
Posted by Chris on 2nd Apr 2015
Not my first time buying these subs. To this day these are my favorite sounding subs. I will continue to buy and use FI products because of their quality. Nothing really bad to say honestly....
Posted by Devin on 6th Mar 2015
I haven't hooked them up yet but man they sure are beastly subs!! Way better than any other sub I've bought in the pass and I had a lot of other "top brands". I should have both hooked up in a week or so and can't wait. I'm happy I went this direction
Posted by Paul Parenti on 18th Feb 2015
This would be my second SP4 15 and I will be starting a full build in a much larger vehicle than my pickup. Even though being in a pickup with a barely put together box, this one 15" was noticeably louder than any other 15 i have come in contact with. Would highly recommend, especially paired with the soundquebed q3500.
Posted by Unknown on 12th Feb 2015
Just installed and a great product from the care in the shipping to the power it puts out looking too by another soon
Posted by Smoove on 15th Dec 2014
Finally have 2 RF T2k's on my SP4's
1:17 of the vid things float
Posted by Matthew WIlliams on 27th Nov 2014
Great Sub. I hooked it up to 2 cresendo s1500s I want to try pushing more power in her and seeing what happens. But all around, killed my 2 15 in power acoustik mofo's out of the water.
Posted by tanner marker on 10th Nov 2014
I have it running on a boundaries 2200 for now and can say it sounds great. Plan on getting a second one soon!
Posted by Rick on 4th Nov 2014
It's been 14 years since my SPL competition days... I built a 9.5 cu ft. ported box 1.5" thick MDF with all-thread bolts, etc... tuned to 32hz for 2 of these 15's in my suburban ( walled w/ all seating ) and holy s**t! these produce some serious SPL and sound amazing doing it. Might be in the high 140's. ( just a guess ) Only running on one amp wired at 2.6 ohms ( Dual 1 ohm version ) with roughly 2200 watts as a test, and I am afraid to strap the two amps together and run 8k to them! I am VERY impressed! Well built! Love the bolts to attach speaker wire or in my case 4GA wire!
Posted by christopher mills on 19th Oct 2014
I went from a re audio mx to this it's twice as loud and better sound quality it slams. Only got 2200 watts going to it and it is still very loud and low rattles house Windows when I pull in driveways. Couldn't imagine it on 3000+ watts, it's worth the wait and the money.
Posted by matthew on 7th Oct 2014
When I got the boxes and open them I was surprised how they came in wooden frames. These subs deffitenly pound and still not broken in
Showing reviews 1-10 of 51 | Next