Fi Audio BTL3 15 D1

15″ subwoofer · dual 1 Ω · 2,500 W RMS

Fs 32.8 HzQts 0.29Vas 0.99 ft³Xmax 1.34″
The published specs don’t add up:

Recommended box

For a sedan, one sub, 2,500 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 volume1.25 ft³ (35.5 L)
Qtc0.38
Fc44 Hz
F3 (−3 dB, no cabin gain)99 Hz
Example box (outside)17 5/16″ × 17 5/16″ × 11 3/16″
Open sealed box in designer

Ported

Net volume2.40 ft³ (68 L)
Tuning (Fb)25 Hz
Portslot 1 3/4 × 16 11/16″, 48 3/16″ long
Port velocity at 2,500 W138 ft/s
F3 (−3 dB, no cabin gain)87 Hz
Example box (outside)31 1/2″ × 18 1/8″ × 14 1/16″
Open ported box in designer
203040506080100150200606672788490HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs32.8 Hz
Qts0.29
Qes0.3
Qms6.61
Vas0.99 ft³
Re (one coil)0.9 Ω
Sd125.6 in²
Xmax1.34″
Vd168.1 in³ calc.
Mms779 g calc.
BL21.9 T·m calc.
EBP109 — suits ported calc.
Sensitivity, 1 W / 1 m87.2 dB calc.

General

Size15″
Voice coilsdual 1 Ω
RMS power2,500 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