For a sedan, one sub, 300 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 Ported · SPL in dB at 1 W / 1 m, no cabin gain
Thiele/Small parameters
Fs
24 Hz
Qts
0.54
Qes
0.61
Qms
5.09
Vas
4.13 ft³
Re
≈ 1.7 Ω
Sd
73 in²
Xmax
≈ 0.39″
Mms
118 g calc.
BL
7 T·m calc.
EBP
39 — suits sealed calc.
Sensitivity, 1 W / 1 m
86.2 dB calc.
General
Size
12″
Voice coils
2 Ω
RMS power
—
Mounting dimensions
Cutout diameter
≈ 11 1/8″
Mounting depth
≈ 5 7/8″
“≈” 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.