Ground Zero GZTW 20TX (2x2 Ohm)

8″ subwoofer · dual 2 Ω · 200 W RMS

39.4 HzFs, resonance

0.54Qts

0.74 ft³Vas

0.47″Xmax

200 WRMS

Source	web.archive.org · manufacturer data
Checked against source	October 2026
Thiele/Small parameters	not in the spec sheet: Re — typical value for the size used
Mounting dimensions	2 of 4 — missing: frame outer diameter, magnet diameter; the designer will use an estimate

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

smaller, tighter

0.60 ft³ (17 L)

Net volume

Bass character (Qtc)	Tight and punchy · 0.80
Fc	59 Hz
F3 (−3 dB, no cabin gain)	55 Hz
Example box (outside)	10 1/4″ × 10 1/4″ × 15 9/16″

Open sealed box in designer

Ported

deeper, louder

0.60 ft³ (17 L)

Net volume

Tuning (Fb)	41 Hz
Port	round port Ø2 1/2″, 11 3/8″ long
Port velocity at 200 W	103 ft/s
F3 (−3 dB, no cabin gain)	42 Hz
Example box (outside)	18″ × 15 3/4″ × 6 1/2″

At 200 W this example’s port will be noisy: air speed 103 ft/s, while the limit is 82 ft/s. It stays quiet up to about 120 W. Full power needs a port of at least 6.2 in², which means a bigger box than this example — size it in the designer.

Open ported box in designer

Deeper: 1.34 ft³ (38 L) tuned to 36 Hz, 31 1/2″ × 15 3/4″ × 9 3/16″ 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 2 Ω
RMS power	200 W
Fs	39.4 Hz
Qts	0.54
Qes	0.63
Qms	3.72
Vas	0.74 ft³

Re (one coil)	≈ 1.7 Ω
Sd	34.5 in²
Xmax	0.47″
Vd	16.3 in³ calc.
Mms	55 g calc.
BL	6.1 T·m calc.
EBP	63 — sealed or ported calc.
Sensitivity, 1 W / 1 m	85.1 dB calc.

Mounting dimensions

Cutout diameter	7 1/4″
Mounting depth	4″

Cone area (Sd) calculated from Fs, Vas and Mms: 34.5 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 Ground Zero 8″ models

Ground Zero GZHW 8SPL-D2 FLAT (2x2 Ohm) 8″ · dual 2 Ω
Ground Zero GZHW 8XSPL-D1 (2x1 Ohm) 8″ · dual 1 Ω
Ground Zero GZHW 20-D1 (2x1 Ohm) 8″ · dual 1 Ω
Ground Zero GZHW 20SPL (2x2 Ohm) 8″ · dual 1 Ω
Ground Zero GZHW 20X (2x2 Ohm) 8″ · dual 2 Ω
Ground Zero GZHW 20XSPL-D1 (2x1 Ohm) 8″ · dual 1 Ω
Ground Zero GZHW 20XSPL-D2 (2x2 Ohm) 8″ · dual 2 Ω
Ground Zero GZIW 200 (4 Ohm) 8″ · 4 Ω
Ground Zero GZIW 200X (4 Ohm) 8″ · 4 Ω
Ground Zero GZIW 200X-II (4 Ohm) 8″ · 4 Ω
Ground Zero GZRW 8FL (2 Ohm) 8″ · 2 Ω
Ground Zero GZRW 8XSPL (2x2 Ohm) 8″ · dual 2 Ω

Similar 8″ subwoofers from other brands

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

Audison Prima APBMW S8-2.2 (BMW/MINI underseat, SVC 2 ohm) 0.53 ft³ sealed · 0.64 ft³ ported
Gladen RS 08 (SVC 4 ohm) 0.42 ft³ sealed · 0.53 ft³ ported
Deaf Bonce Apocalypse DB-SA2508 D2 0.67 ft³ sealed · 0.57 ft³ ported
Cadence S1W8D4.v2 0.64 ft³ sealed · 0.71 ft³ ported
Morel Ultimo Titanium 804 (SVC 4 ohm) 0.46 ft³ sealed · 0.64 ft³ ported
Dayton Audio PCS8-4 0.42 ft³ sealed · 0.57 ft³ ported

FAQ

What box does the Ground Zero GZTW 20TX (2x2 Ohm) need?

Recommended net volume: 0.60 ft³ sealed, 0.60 ft³ ported tuned to 41 Hz — for one sub in a sedan at 200 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.

What are the Ground Zero GZTW 20TX (2x2 Ohm) Thiele/Small specs?

Fs 39.4 Hz, Qts 0.54, Vas 0.74 ft³, Xmax 0.47″, Sd 34.5 in².

What is the Ground Zero GZTW 20TX (2x2 Ohm) mounting depth?

Mounting depth is 4″, cutout diameter 7 1/4″. The inside depth of the box must exceed the mounting depth by at least 1″.

How much power does the Ground Zero GZTW 20TX (2x2 Ohm) handle and how do I wire it?

RMS power rating: 200 W. Dual 2 Ω voice coils: series gives 4 Ω, parallel gives 1 Ω at the amp. Wiring for several subs and amp power — in the wiring calculator.