JBL 1800GTi

18″ subwoofer · 4 Ω · 600 W RMS

Fs 30 HzQts 0.43Vas 12.81 ft³Xmax 0.22″

Recommended box

For a sedan, one sub, 600 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 volume4.48 ft³ (127 L)
Qtc0.85
Fc59 Hz
F3 (−3 dB, no cabin gain)54 Hz
Example box (outside)31 1/2″ × 20 7/8″ × 15 1/2″
Open sealed box in designer

Ported

Net volume7.63 ft³ (216 L)
Tuning (Fb)40 Hz
Portslot 2 3/4 × 19 7/16″, 5 11/16″ long
Port velocity at 600 W64 ft/s
F3 (−3 dB, no cabin gain)39 Hz
Example box (outside)31 1/2″ × 20 7/8″ × 25 3/8″
Open ported box in designer
2030405060801001502007278849096102HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs30 Hz
Qts0.43
Qes0.46
Qms6.77
Vas12.81 ft³
Re2.5 Ω
Sd196.9 in²
Xmax0.22″
Vd42.6 in³ calc.
Mms177 g calc.
BL13.5 T·m calc.
EBP65 — sealed or ported calc.
Sensitivity, 1 W / 1 m95.3 dB calc.

General

Size18″
Voice coils4 Ω
RMS power600 W

Mounting dimensions

Ø18 1/4″cutout Ø16 7/8″mounting depth 6 13/16″magnet Ø≈ 11″
Cutout diameter16 7/8″
Mounting depth6 13/16″
Overall diameter18 1/4″

“≈” 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