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 55 | Next
Posted by josh on 25th Jul 2015
These subs get surprisingly loud for how low they hit. I hit 150.2 db @ 30 hertz with 2 of them with all my settings down somewhat cuz they're still new and breaking in. The sp4s have an awesome look to them and an even better sound. I'm definitely going to be getting other Fi products for my other car now
Posted by Unknown on 8th Jul 2015
This sub is amazing from hitting all the lows to spl in general definitely would recommend for any one who loves bass #beastmode
Posted by Ruben on 7th May 2015
I just recently purchased and received my first Sp4 15" and I got to say the wait was all worth waiting for I am completely in love am running it with a Rockford Fosgate Power T3000.1bd rated at 3,612 @ 1ohm. And it takes it like a champ I am very impressed with the over all craftsmanship, performanceI and of course the great customer service Fi Audio has. I been running it for about a month and is still getting broken in and louder and louder with the Low. I will definitely be a Fi Audio customer for years to come
Posted by Desiree Davis on 26th Apr 2015
Very satisfied with this sub and it's worth every dollar. This is my third fi sub so excellence was expected but, I was not ready for this much.
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.
Showing reviews 1-10 of 55 | Next