Fi Audio Q18 D2

18″ subwoofer · dual 2 Ω · 1,750 W RMS

Fs 27.9 HzQts 0.51Vas 5.80 ft³Xmax 1.34″

Recommended box

For a sedan, one sub, 1,750 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 volume3.96 ft³ (112 L)
Qtc0.80
Fc44 Hz
F3 (−3 dB, no cabin gain)41 Hz
Example box (outside)31 1/2″ × 20 7/8″ × 13 15/16″
Open sealed box in designer

Ported

Net volume7.27 ft³ (206 L)
Tuning (Fb)30 Hz
Portslot 4 1/2 × 19 7/16″, 28 3/16″ long
Port velocity at 1,750 W63 ft/s
F3 (−3 dB, no cabin gain)27 Hz
Example box (outside)31 1/2″ × 20 7/8″ × 28 3/8″
Open ported box in designer
203040506080100150200667278849096HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs27.9 Hz
Qts0.51
Qes0.54
Qms9.17
Vas5.80 ft³
Re (one coil)1.8 Ω
Sd187.6 in²
Xmax1.34″
Vd251.1 in³ calc.
Mms411 g calc.
BL15.5 T·m calc.
EBP52 — sealed or ported calc.
Sensitivity, 1 W / 1 m90.2 dB calc.

General

Size18″
Voice coilsdual 2 Ω
RMS power1,750 W

Mounting dimensions

Ø18 3/4″cutout Ø16 3/4″mounting depth 9 1/2″magnet Ø≈ 10 7/8″
Cutout diameter16 3/4″
Mounting depth9 1/2″
Overall diameter18 3/4″

“≈” 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 18″ models