Sundown Audio U-8 D2

8″ subwoofer · dual 2 Ω · 750 W RMS

Fs 39.4 HzQts 0.35Vas 0.22 ft³Xmax 0.71″

Recommended box

For a sedan, one sub, 750 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

Net volume0.32 ft³ (9 L)
Qtc0.46
Fc51 Hz
F3 (−3 dB, no cabin gain)91 Hz
Example box (outside)10 5/8″ × 10 5/8″ × 8 5/8″
Open sealed box in designer

Ported

Net volume0.64 ft³ (18 L)
Tuning (Fb)28 Hz
Portslot 1 15/16 × 14 5/16″, 146 15/16″ long
Port velocity at 750 W41 ft/s
F3 (−3 dB, no cabin gain)72 Hz
Example box (outside)31 1/2″ × 15 3/4″ × 14 13/16″

The volume and tuning are the recommendation, but the port doesn’t fit this example box. Size the box and port in the designer.

Open ported box in designer
2030405060801001502006066727884HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs39.4 Hz
Qts0.35
Qes0.412
Qms2.47
Vas0.22 ft³
Re (one coil)1.9 Ω
Sd34 in²
Xmax0.71″
Vd24.1 in³ calc.
Mms175 g calc.
BL14.1 T·m calc.
EBP96 — sealed or ported calc.
Sensitivity, 1 W / 1 m81.7 dB calc.

General

Size8″
Voice coilsdual 2 Ω
RMS power750 W

Mounting dimensions

Ø8 11/16″cutout Ø7 3/8″mounting depth 6″magnet Ø6 7/8″
Cutout diameter7 3/8″
Mounting depth6″
Overall diameter8 11/16″
Magnet diameter6 7/8″

The spec sheet's Sd of 53.4 in² is the area of a 8″ circle, not the cone's radiating area — not used.

Cone area (Sd) calculated from Fs, Vas and Mms: 34 in².

“≈” 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.

Data sources

Other Sundown Audio 8″ models