Rockford Fosgate Punch HE2 RFP4108

8″ subwoofer · dual 2 Ω · 250 W RMS

38 HzFs, resonance
0.39Qts
0.35 ft³Vas
0.43″Xmax
250 WRMS

Recommended box

For a sedan, one sub, 250 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

smaller, tighter
0.28 ft³ (8 L)
Net volume
Qtc0.58
Fc57 Hz
F3 (−3 dB, no cabin gain)75 Hz
Example box (outside)10 1/4″ × 10 1/4″ × 8 1/2″
Open sealed box in designer

Ported

deeper, louder
0.60 ft³ (17 L)
Net volume
Tuning (Fb)42 Hz
Portround port Ø2 1/2″, 10 3/4″ long
Port velocity at 250 W159 ft/s
F3 (−3 dB, no cabin gain)37 Hz
Example box (outside)15 11/16″ × 15 3/4″ × 7 1/16″
Open ported box in designer
203040506080100150200606672788490HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs38 Hz
Qts0.39
Qes0.41
Qms6.46
Vas0.35 ft³
Re (one coil)1.63 Ω
Sd31 in²
Xmax0.43″
Vd13.4 in³ calc.
Mms99 g calc.
BL9.7 T·m calc.
EBP93 — sealed or ported calc.
Sensitivity, 1 W / 1 m83.3 dB calc.

General

Size8″
Voice coilsdual 2 Ω
RMS power250 W

Mounting dimensions

Ø8 7/16″cutout Ø7 1/16″mounting depth 4 11/16″magnet Ø≈ 4 9/16″
Cutout diameter7 1/16″
Mounting depth4 11/16″
Overall diameter8 7/16″

Judging by its value, the published Re is for both coils in series — converted to per coil.

“≈” 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 Rockford Fosgate 8″ models