For a sedan, one sub, 700 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
25.6 Hz
Qts
0.48
Qes
0.509
Qms
8.28
Vas
4.55 ft³
Re (one coil)
3.48 Ω
Sd
130.2 in²
Xmax
0.67″
Vd
87.1 in³ calc.
Mms
301 g calc.
BL
18.2 T·m calc.
EBP
50 — sealed or ported calc.
Sensitivity, 1 W / 1 m
88.3 dB calc.
General
Size
15″
Voice coils
dual 4 Ω
RMS power
700 W
Mounting dimensions
Cutout diameter
13 3/4″
Mounting depth
8 3/16″
Magnet diameter
7 1/8″
“≈” 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.