ESX SX840 (4 Ohm)

8″ subwoofer · 4 Ω · 300 W RMS

Fs 35 HzQts 0.38Vas 0.88 ft³Xmax 0.16″

Recommended box

For a sedan, one sub, 300 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)
Qtc0.74
Fc68 Hz
F3 (−3 dB, no cabin gain)70 Hz
Example box (outside)10 5/8″ × 10 5/8″ × 8 5/8″
Open sealed box in designer

Ported

Net volume0.81 ft³ (23 L)
Tuning (Fb)38 Hz
Portround port Ø3″, 13 13/16″ long
Port velocity at 300 W122 ft/s
F3 (−3 dB, no cabin gain)37 Hz
Example box (outside)22 1/16″ × 15 3/4″ × 6 7/8″
Open ported box in designer
203040506080100150200606672788490HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs35 Hz
Qts0.38
Qes0.41
Qms4.9
Vas0.88 ft³
Re3.6 Ω
Sd33.2 in²
Xmax0.16″
Vd5.2 in³ calc.
Mms54 g calc.
BL10.2 T·m calc.
EBP85 — sealed or ported calc.
Sensitivity, 1 W / 1 m86.2 dB calc.

General

Size8″
Voice coils4 Ω
RMS power300 W

Mounting dimensions

Ø≈ 8 5/8″cutout Ø7 7/16″mounting depth 4 1/2″magnet Ø≈ 4 13/16″
Cutout diameter7 7/16″
Mounting depth4 1/2″

“≈” 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 ESX 8″ models