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
35.4 Hz
Qts
0.56
Qes
0.63
Qms
5.31
Vas
2.50 ft³
Re
3.2 Ω
Sd
78.4 in²
Xmax
0.28″
Vd
21.6 in³ calc.
Mms
104 g calc.
BL
10.8 T·m calc.
EBP
56 — sealed or ported calc.
Sensitivity, 1 W / 1 m
89 dB calc.
General
Size
12″
Voice coils
4 Ω
RMS power
300 W
Mounting dimensions
Cutout diameter
10 7/8″
Mounting depth
5 13/16″
Overall diameter
12 1/16″
“≈” 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.