Rockford Fosgate Power T3-BMW-SUB

8″ subwoofer · 4 Ω · 150 W RMS

Fs 38 HzQts 0.49Vas 1.43 ft³Xmax 0.24″

Recommended box

For a sedan, one sub, 150 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 volume0.78 ft³ (22 L)
Qtc0.83
Fc64 Hz
F3 (−3 dB, no cabin gain)59 Hz
Example box (outside)31 1/2″ × 15 3/4″ × 4 11/16″
Open sealed box in designer

Ported

Net volume1.31 ft³ (37 L)
Tuning (Fb)44 Hz
Portslot 1 9/16 × 14 5/16″, 19 15/16″ long
Port velocity at 150 W34 ft/s
F3 (−3 dB, no cabin gain)41 Hz
Example box (outside)31 1/2″ × 15 3/4″ × 8 3/16″
Open ported box in designer
203040506080100150200667278849096HzdB
Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Fs38 Hz
Qts0.49
Qes0.534
Qms6
Vas1.43 ft³
Re≈ 3.4 Ω
Sd≈ 33.3 in²
Xmax0.24″
EBP71 — sealed or ported calc.
Sensitivity, 1 W / 1 m88.2 dB calc.

General

Size8″
Voice coils4 Ω
RMS power150 W

Mounting dimensions

Ø8 1/2″cutout Ø7 11/16″mounting depth 1 1/4″magnet Ø≈ 5″
Cutout diameter7 11/16″
Mounting depth1 1/4″
Overall diameter8 1/2″

Only Qts is published — Qms assumed to be 6 and Qes calculated (barely affects box design).

“≈” 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