Sundown Audio U-8 D4

8″ subwoofer · dual 4 Ω · 750 W RMS

Fs 41.3 HzQts 0.43Vas 0.25 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)
Qtc0.57
Fc55 Hz
F3 (−3 dB, no cabin gain)73 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)40 Hz
Portround port Ø2 1/2″, 11 1/4″ long
Port velocity at 750 W268 ft/s
F3 (−3 dB, no cabin gain)35 Hz
Example box (outside)13 1/2″ × 15 3/4″ × 8 7/16″
Open ported box in designer
2030405060801001502006066727884HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs41.3 Hz
Qts0.43
Qes0.519
Qms2.54
Vas0.25 ft³
Re (one coil)3.17 Ω
Sd34 in²
Xmax0.71″
Vd24.1 in³ calc.
Mms145 g calc.
BL15.2 T·m calc.
EBP80 — sealed or ported calc.
Sensitivity, 1 W / 1 m81.8 dB calc.

General

Size8″
Voice coilsdual 4 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