Fi Audio SP4 15v2+ D2

15″ subwoofer · dual 2 Ω · 3,500 W RMS

Fs 27.6 HzQts 0.32Vas 2.51 ft³Xmax 1.30″

Recommended box

For a sedan, one sub, 3,500 W. It’s the same math as the designer’s step-by-step mode, where you can fit the box to your space, vehicle and amp and get plans, a cut sheet and DXF.

Sealed

Net volume1.59 ft³ (45 L)
Qtc0.51
Fc44 Hz
F3 (−3 dB, no cabin gain)69 Hz
Example box (outside)17 5/16″ × 17 5/16″ × 13 1/2″
Open sealed box in designer

Ported

Net volume2.40 ft³ (68 L)
Tuning (Fb)29 Hz
Portslot 2 9/16 × 16 11/16″, 51 1/8″ long
Port velocity at 3,500 W110 ft/s
F3 (−3 dB, no cabin gain)29 Hz
Example box (outside)31 1/2″ × 18 1/8″ × 15 5/8″
Open ported box in designer
203040506080100150200606672788490HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs27.6 Hz
Qts0.32
Qes0.33
Qms8.76
Vas2.51 ft³
Re (one coil)1.27 Ω
Sd125.6 in²
Xmax1.30″
Vd163.1 in³ calc.
Mms435 g calc.
BL17 T·m calc.
EBP84 — sealed or ported calc.
Sensitivity, 1 W / 1 m88.6 dB calc.

General

Size15″
Voice coilsdual 2 Ω
RMS power3,500 W

Mounting dimensions

Ø15 5/8″cutout Ø14 1/8″mounting depth 11″magnet Ø≈ 9 3/16″
Cutout diameter14 1/8″
Mounting depth11″
Overall diameter15 5/8″

“≈” means the value isn’t in the spec sheet and a typical value for the size is used; “calc.” means it’s calculated from the published parameters. Check the manufacturer’s spec sheet before you build.

Data sources

Other Fi Audio 15″ models