Hertz Energy ES F20.5 (free-air/shallow, SVC 4 ohm)

8″ subwoofer · 4 Ω · 200 W RMS

Fs 52 HzQts 0.40Vas 0.47 ft³Xmax 0.20″

Recommended box

For a sedan, one sub, 200 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)
Qtc0.64
Fc82 Hz
F3 (−3 dB, no cabin gain)96 Hz
Example box (outside)10 1/4″ × 10 1/4″ × 9 1/4″
Open sealed box in designer

Ported

Net volume0.67 ft³ (19 L)
Tuning (Fb)48 Hz
Portslot 1 9/16 × 14 5/16″, 35 1/8″ long
Port velocity at 200 W33 ft/s
F3 (−3 dB, no cabin gain)46 Hz
Example box (outside)31 1/2″ × 15 3/4″ × 6 3/4″
Open ported box in designer
203040506080100150200606672788490HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs52 Hz
Qts0.40
Qes0.46
Qms3.38
Vas0.47 ft³
Re2.9 Ω
Sd34.2 in²
Xmax0.20″
Vd6.7 in³ calc.
Mms49 g calc.
BL10 T·m calc.
EBP113 — suits ported calc.
Sensitivity, 1 W / 1 m88.1 dB calc.

General

Size8″
Voice coils4 Ω
RMS power200 W

Mounting dimensions

Ø8 1/4″cutout Ø7 1/8″mounting depth 2 13/16″magnet Ø≈ 4 5/8″
Cutout diameter7 1/8″
Mounting depth2 13/16″
Overall diameter8 1/4″

Cone area (Sd) calculated from Fs, Vas and Mms: 34.2 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 Hertz 8″ models