Fi Audio HT-3 18 S4

18″ subwoofer · 4 Ω · 2,000 W RMS

Fs 21.3 HzQts 0.42Vas 8.33 ft³Xmax 1.34″

Recommended box

For a sedan, one sub, 2,000 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 volume3.21 ft³ (91 L)
Qtc0.80
Fc40 Hz
F3 (−3 dB, no cabin gain)38 Hz
Example box (outside)31 1/2″ × 20 7/8″ × 11 3/4″
Open sealed box in designer

Ported

Net volume7.27 ft³ (206 L)
Tuning (Fb)26 Hz
Portslot 4 5/16 × 19 7/16″, 38 3/16″ long
Port velocity at 2,000 W64 ft/s
F3 (−3 dB, no cabin gain)24 Hz
Example box (outside)31 1/2″ × 20 7/8″ × 29 7/8″
Open ported box in designer
203040506080100150200667278849096HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs21.3 Hz
Qts0.42
Qes0.45
Qms6.94
Vas8.33 ft³
Re3.3 Ω
Sd187.6 in²
Xmax1.34″
Vd251.1 in³ calc.
Mms491 g calc.
BL21.9 T·m calc.
EBP47 — suits sealed calc.
Sensitivity, 1 W / 1 m89.1 dB calc.

General

Size18″
Voice coils4 Ω
RMS power2,000 W

Mounting dimensions

Ø18 1/2″cutout Ø16 3/4″mounting depth 6 1/2″magnet Ø≈ 10 7/8″
Cutout diameter16 3/4″
Mounting depth6 1/2″
Overall diameter18 1/2″

“≈” 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