Fi Audio SSD18 D1

18″ subwoofer · dual 1 Ω · 1,500 W RMS

Fs 27.6 HzQts 0.45Vas 3.23 ft³Xmax 0.87″
The published specs don’t add up:

Recommended box

For a sedan, one sub, 1,500 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 volume1.84 ft³ (52 L)
Qtc0.75
Fc46 Hz
F3 (−3 dB, no cabin gain)46 Hz
Example box (outside)20 1/16″ × 20 1/16″ × 11 15/16″
Open sealed box in designer

Ported

Net volume4.87 ft³ (138 L)
Tuning (Fb)27 Hz
Portslot 3 3/8 × 19 7/16″, 42 5/16″ long
Port velocity at 1,500 W64 ft/s
F3 (−3 dB, no cabin gain)25 Hz
Example box (outside)31 1/2″ × 20 7/8″ × 22 3/16″
Open ported box in designer
203040506080100150200606672788490HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs27.6 Hz
Qts0.45
Qes0.48
Qms7.14
Vas3.23 ft³
Re (one coil)0.75 Ω
Sd187.6 in²
Xmax0.87″
Vd162.4 in³ calc.
Mms755 g calc.
BL14.3 T·m calc.
EBP58 — sealed or ported calc.
Sensitivity, 1 W / 1 m88 dB calc.

General

Size18″
Voice coilsdual 1 Ω
RMS power1,500 W

Mounting dimensions

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