Fi Audio BTL4 15 D1

15″ subwoofer · dual 1 Ω · 3,500 W RMS

Fs 27.1 HzQts 0.47Vas 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 volume1.27 ft³ (36 L)
Qtc0.80
Fc47 Hz
F3 (−3 dB, no cabin gain)44 Hz
Example box (outside)17 5/16″ × 17 5/16″ × 11 5/16″
Open sealed box in designer

Ported

Net volume4.20 ft³ (119 L)
Tuning (Fb)26 Hz
Portslot 5 1/8 × 16 11/16″, 72 3/4″ long
Port velocity at 3,500 W68 ft/s
F3 (−3 dB, no cabin gain)24 Hz
Example box (outside)31 1/2″ × 18 1/8″ × 30 3/16″
Open ported box in designer
203040506080100150200606672788490HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs27.1 Hz
Qts0.47
Qes0.5
Qms6.71
Vas2.51 ft³
Re (one coil)0.7 Ω
Sd125.6 in²
Xmax1.30″
Vd163.1 in³ calc.
Mms451 g calc.
BL10.4 T·m calc.
EBP54 — sealed or ported calc.
Sensitivity, 1 W / 1 m86.5 dB calc.

General

Size15″
Voice coilsdual 1 Ω
RMS power3,500 W

Mounting dimensions

Ø15 5/8″cutout Ø14 1/8″mounting depth 8 3/4″magnet Ø≈ 9 3/16″
Cutout diameter14 1/8″
Mounting depth8 3/4″
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