For a sedan, one sub, 400 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
47 Hz
Qts
0.53
Qes
0.61
Qms
4.3
Vas
0.18 ft³
Re (one coil)
≈ 1.7 Ω
Sd
31.2 in²
Xmax
0.53″
Vd
16.6 in³ calc.
Mms
126 g calc.
BL
10.2 T·m calc.
EBP
77 — sealed or ported calc.
Sensitivity, 1 W / 1 m
81.5 dB calc.
General
Size
8″
Voice coils
dual 2 Ω
RMS power
400 W
Mounting dimensions
Cutout diameter
7 5/16″
Mounting depth
4 15/16″
Overall diameter
8 1/2″
Magnet diameter
6″
“≈” 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.