Fi Car Audio SP4 PLUS 15

Code: FI-SP4PLUS15

The 2019 SP4 PLUS Series is designed for monster daily driving systems requiring high linearity and extreme power handling.


In Stock

Ohm *

Tinsel Leads *

Dustcaps *

Spiders *

Cooling *

Dust Cap Logo Colour *

Disclaimer *

There are special terms & conditions related to this product.


The SP4 PLUS Series is the latest in the progression of Fi SP4 series of subwoofers geared towards thundering daily drivers. Adding a second 10″ high grade magnet provides the increased Gauss over the standard SP4 while 4 Fi designed 10″ heavy progressive spiders keep things under mechanical control. With a monster 4″ voicecoil for increased thermal capacity and proprietary US made steel water jet and machined in house on one of our CNC machines ensures that there is no shortage of motor force in the FEA derived design. The PLUS series also includes an aluminum pole compression plug and an open motor geometry, increasing thermal capacity. Utilizing a special 144 tinsel count leadwire there are no losses with power transfer to the coil.

The 2019 SP4 PLUS Series is designed for monster daily driving systems requiring high linearity and extreme power handling. With the increased motor force it becomes even more of a power house under high compression applications maintaining motor force where the standard version my start to drop off.


Coils DUAL 1 | DUAL 2
FS 27.5 Hz | 27.6
RE 0.65 | 1.27
QMS 8.76
QES 0.33
QTS 0.32
MMS 438g | 432g
CMS 0.784
SD 810cm^2 | 810cm^2
VAS 71.0 l
SPL 88.4 dB 1w/1m
BL 17.18 N/A | 24.02N/A
XMAX 33mm (One Way)
RMS 3500W

Overall Diameter 15.625”
Cutout Diameter 14.125”
Mounting Depth 11.00”
Driver Displacement 0.21cuft
Sealed Box 2-3.5 cuft
Ported Box 3-5 cuft

Dual 1 and Dual 2 Ohm
Extra heavy aluminum basket
Wrap around gasket
Kraft pulp fiber reinforced cone
Dual layer wide foam surround
Standard heavy duty stitched lead or Hybrid stitched FOAD system
144 tinsel count leads
FEA optimized motor
Open column motor design
4” diameter 4 layer coil (Flatwind standard)
Dual high grade magnet
Four progressive 10″ spiders
Water jet and machined in house at Fi

Custom Options Explained


“Fi Terms & Conditions”



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Additional information

Weight 34.00 kg


UK Delivery

All items ordered before 14.00pm are shipped the same day unless otherwise stated at the time of ordering. Orders placed after 14.00pm on a Friday will be shipped the following Monday (excluding bank holidays, in which case it will be the next working day). If the item is out of stock for whatever reason you will be emailed within 24hrs to inform you of this. Our site manages stock inventory so if it says ‘IN STOCK’ that means goods are available for immediate dispatch.

  • Shipping will be calculated at the checkout.
  • Free shipping available for customers in the UK mainland ONLY when orders are over £50.
  • We use Interlink Express for all UK next day deliveries (aswell as for orders over £50 if the weight exceeds 2kg) and Royal Mail Recorded Post for orders under 2kg.

Make sure you supply us with a mobile number when you order, then we can give you full tracking information & updates on your order throughout the process.

Clicking on the above image, will also allow you to track your order online. If you have any questions or queries, contact our helpful office team on

Free Delivery

Free delivery is available to UK mainland addresses ONLY and excludes addresses in the Scottish Highlands & Islands and Northern Ireland. Free delivery is applicable to orders over £50.00 (inc vat) ONLY. This offer doesn’t necessarily mean your goods will be sent on a courier next day service. However assuming the weight exceeds 2kg your goods are usually sent via courier (Interlink Express).

Guranteed 24 Hour

  • Next Day Delivery – Over £50 Inc. VAT – Any weight – Free!
  • Next Day Delivery – 2-5KG – £8.00
  • Next Day Delivery – 5-20KG – £9.99
  • Next Day Delivery – 20-30KG – £11.99
  • Next Day Delivery – 30-40KG – £15.00
  • Next Day Delivery – 45KG+ – £50.00


  • Royal Mail 1st Class Recorded 1-3 working days – Upto 1KG – £4.45
  • Royal Mail 1st Class Recorded 1-3 working days – Upto 1-2KG – £6.90
  • Royal Mail 2nd Class Recorded 2-5 working days – 0-2KG – £3.95


  • Royal Mail Special Delivery Saturday – Upto 2KG – £14.00
  • Courier Saturday – Upto 5KG – £15.95
  • Courier Saturday – 5-20KG – £19.95
  • Courier Saturday – 20-25KG – £22.95

Orders MUST be made before 2pm Friday

Back Order

Items that are listed with ‘Back order’ usually means there is around a 5-10 working day delay for the item to be back in stock. Some items are listed in this way as they are a low volume product and are considered special order with our suppliers.

European & International Delivery

Blade ICE ships internationally to many countries in Europe. Based on the weight of your order shipping will be calculated at the checkout.

Blade ICE reserves the right to charge the full shipping fee applicable to resend if the item is returned to us as the customer was unable to take delivery of the parcel for any reason. Courier returned items will be added back into our stock and your account credited with the order total, minus the fee the courier charges us to deliver the item back to us. You will have to re-place the order to have the item reshipped. If a customer inputs any incorrect details on their order, which causes the parcel to be delivered incorrectly, we will not hold any responsibility for this parcel.

Finally we advise you to check the contents of the order with the inventory sent with the goods. In the rare instance that goods are missing, please contact us within 24 hours and we will happily send out the missing goods at no extra cost to you. If goods are damaged or faulty please inform us within 3 working days of receiving your order.

Please refer to our Terms and Conditions for more information.

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