For a sedan, one sub, 250 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
23 Hz
Qts
0.52
Qes
0.62
Qms
3.2
Vas
6.76 ft³
Re
3.6 Ω
Sd
135.8 in²
Xmax
0.35″
Vd
48.1 in³ calc.
Mms
272 g calc.
BL
15.1 T·m calc.
EBP
37 — suits sealed calc.
Sensitivity, 1 W / 1 m
87.8 dB calc.
General
Size
15″
Voice coils
4 Ω
RMS power
250 W
Mounting dimensions
Cutout diameter
13 7/8″
Mounting depth
6 15/16″
“≈” 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.