Quantum Audio QW3000/8D4

8″ subwoofer · dual 4 Ω

40.7 HzFs, resonance

0.51Qts

0.26 ft³Vas

0.60″Xmax

Source	web.archive.org · manufacturer data
Checked against source	October 2026
Thiele/Small parameters	complete
Mounting dimensions	0 of 4 — missing: cutout, mounting depth, frame outer diameter, magnet diameter; the designer will use an estimate

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

smaller, tighter

0.28 ft³ (8 L)

Net volume

Bass character (Qtc)	Flat and accurate · 0.71
Fc	56 Hz
F3 (−3 dB, no cabin gain)	59 Hz
Example box (outside)	10 5/8″ × 10 5/8″ × 7 7/8″

Open sealed box in designer

Ported

deeper, louder

0.53 ft³ (15 L)

Net volume

Tuning (Fb)	45 Hz
Port	round port Ø2 1/2″, 10 9/16″ long
Port velocity at 300 W	163 ft/s
F3 (−3 dB, no cabin gain)	38 Hz
Example box (outside)	15 5/8″ × 15 3/4″ × 6 1/2″

At 300 W this example’s port will be noisy: air speed 163 ft/s, while the limit is 82 ft/s. It stays quiet up to about 75 W. Full power needs a port of at least 9.9 in², which means a bigger box than this example — size it in the designer.

Open ported box in designer

Deeper: 0.64 ft³ (18 L) tuned to 37 Hz, 19″ × 15 3/4″ × 6 1/2″ outside — a bigger box with flatter deep bass. Open in the calculator

Where to buy Amazon

Sealed Ported · SPL in dB at 1 W / 1 m, no cabin gain

Thiele/Small parameters

Size	8″
Voice coils	dual 4 Ω
RMS power	—
Fs	40.7 Hz
Qts	0.51
Qes	0.585
Qms	4.15
Vas	0.26 ft³

Re (one coil)	3.2 Ω
Sd	32.8 in²
Xmax	0.60″
Vd	19.6 in³ calc.
Mms	133 g calc.
BL	13.7 T·m calc.
EBP	70 — sealed or ported calc.
Sensitivity, 1 W / 1 m	81.2 dB calc.

Mounting dimensions

Cutout diameter	≈ 7 5/16″
Mounting depth	≈ 3 15/16″

Cone area (Sd) calculated from Fs, Vas and Mms: 32.8 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

web.archive.org/web/20240624174010/https://quantumaudio.net/wp-content/uploads/2

Other Quantum Audio 8″ models

Quantum Audio QPW3000/8D4 8″ · dual 4 Ω
Quantum Audio QWX4000/8D4 8″ · dual 4 Ω

Similar 8″ subwoofers from other brands

Close in Fs, Qts and Vas — a box of similar volume will suit them.

Sundown Audio Ev5-8 D4 0.28 ft³ sealed · 0.49 ft³ ported
Sundown Audio HZ-8 D4 0.28 ft³ sealed · 0.49 ft³ ported
CT Sounds TROPO-8 D4 0.28 ft³ sealed · 0.42 ft³ ported
DD Audio 608f D2 0.34 ft³ sealed · 0.99 ft³ ported
DD Audio 608f D4 0.34 ft³ sealed · 0.99 ft³ ported
Cadence S2W8D2 0.32 ft³ sealed · 0.53 ft³ ported

FAQ

What box does the Quantum Audio QW3000/8D4 need?

Recommended net volume: 0.28 ft³ sealed, 0.53 ft³ ported tuned to 45 Hz — for one sub in a sedan at 300 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.

What are the Quantum Audio QW3000/8D4 Thiele/Small specs?

Fs 40.7 Hz, Qts 0.51, Vas 0.26 ft³, Xmax 0.60″, Sd 32.8 in².