Sundown Audio M18 D2

18″ subwoofer · dual 2 Ω · 2,000 W RMS

Fs 25.7 HzQts 0.65Vas 4.15 ft³Xmax 1.38″

Recommended box

For a sedan, one sub, 2,000 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 volume4.17 ft³ (118 L)
Qtc0.92
Fc36 Hz
F3 (−3 dB, no cabin gain)31 Hz
Example box (outside)19 11/16″ × 19 11/16″ × 24 7/16″
Open sealed box in designer

Ported

Net volume7.06 ft³ (200 L)
Tuning (Fb)26 Hz
Portslot 4 5/16 × 19 1/16″, 38 11/16″ long
Port velocity at 2,000 W63 ft/s
F3 (−3 dB, no cabin gain)22 Hz
Example box (outside)31 1/2″ × 20 1/2″ × 29 13/16″
Open ported box in designer
203040506080100150200667278849096HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs25.7 Hz
Qts0.65
Qes0.74
Qms5.38
Vas4.15 ft³
Re (one coil)2.06 Ω
Sd182.2 in²
Xmax1.38″
Vd251.1 in³ calc.
Mms639 g calc.
BL16.9 T·m calc.
EBP35 — suits sealed calc.
Sensitivity, 1 W / 1 m86.3 dB calc.

General

Size18″
Voice coilsdual 2 Ω
RMS power2,000 W

Mounting dimensions

Ø18 7/16″cutout Ø16 11/16″mounting depth 14 1/16″magnet Ø7 7/8″
Cutout diameter16 11/16″
Mounting depth14 1/16″
Overall diameter18 7/16″
Magnet diameter7 7/8″

The spec sheet's Sd of 254.5 in² is the area of a 18″ circle, not the cone's radiating area — not used.

Cone area (Sd) calculated from Fs, Vas and Mms: 182.2 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 18″ models