Soundstream XXX-18

18″ subwoofer · 1 Ω · 10,000 W RMS

Specs

22.3 HzFs

0.18Qts

5.50 ft³Vas

1.38″Xmax

All Thiele/Small parameters ↓

Weight & fit

11 1/8″Mounting depth

16 3/4″Cutout

10,000 WRMS · 1 Ω

Mounting drawing ↓

Box size

2.28 ft³ sealedoutside 20 1/16″ × 20 1/16″ × 13 5/8″ · F3 108 Hz

4.41 ft³ ported, 30 Hz31 1/4″ × 20 7/8″ × 23 1/16″ · port: slot 4 5/16 × 19 7/16″, 49 1/16″ long

Box details and plans ↓

The Soundstream XXX-18 is a 18″ subwoofer. With Qts 0.18 and EBP 117 it suits a ported box: deeper and louder; sealed, the bass sounds a bit dry. Long excursion (Xmax 1.38″) — built for loud music and high power.

Open ported box in designer Open sealed box in designer

Source	web.archive.org · manufacturer data
Checked against source	October 2026
Thiele/Small parameters	complete
Mounting dimensions	2 of 4 — missing: frame outer diameter, magnet diameter; the designer will use an estimate

The published specs don’t add up:

Sd of 149.1 in² is unusual for a 18″ (typically 151.9–209.3 in²).
This sub has 4 voice coils — wiring options are calculated as for a single coil; check the final impedance against the spec sheet.

Recommended box

For a sedan, one sub, 10,000 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

2.28 ft³ (64.5 L)

Net volume

Bass character (Qtc)	Dry and tight · 0.34
Fc	41 Hz
F3 (−3 dB, no cabin gain)	108 Hz
Example box (outside)	20 1/16″ × 20 1/16″ × 13 5/8″

Open sealed box in designer

Ported

deeper, louder

4.41 ft³ (125 L)

Net volume

Tuning (Fb)	30 Hz
Port	slot 4 5/16 × 19 7/16″, 49 1/16″ long
Port velocity at 10,000 W	142 ft/s
F3 (−3 dB, no cabin gain)	91 Hz
Example box (outside)	31 1/4″ × 20 7/8″ × 23 1/16″

At 10,000 W this example’s port will be noisy: air speed 142 ft/s, while the limit is 82 ft/s. It stays quiet up to about 3,300 W. Full power needs a port of at least 146.1 in², which means a bigger box than this example — size it in the designer.

Open ported box in designer

Deeper: 2.86 ft³ (81 L) tuned to 27 Hz, 25 5/16″ × 20 7/8″ × 18 5/16″ 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	18″
Voice coils	1 Ω
RMS power	10,000 W
Fs	22.3 Hz
Qts	0.18
Qes	0.191
Qms	5.87
Vas	5.50 ft³

Re	1.2 Ω
Sd	149.1 in²
Xmax	1.38″
Vd	205.4 in³ calc.
Mms	429 g calc.
BL	19.4 T·m calc.
EBP	117 — suits ported calc.
Sensitivity, 1 W / 1 m	91.6 dB calc.

Mounting dimensions

Cutout diameter	16 3/4″
Mounting depth	11 1/8″

“≈” 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/20241206221935/https://www.soundstream.com/manuals/2009/XXX%

Similar 18″ subwoofers from other brands

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

Pride ST 18 D0.5 2.33 ft³ sealed · 6.07 ft³ ported
Kicker SoloX 18" 2-Ohm DVC (S18X2) 2.12 ft³ sealed · 6.53 ft³ ported
Pride S V.3 18 D1 2.31 ft³ sealed · 6.07 ft³ ported
Pride S V.3 18 D2 2.31 ft³ sealed · 6.07 ft³ ported
Resilient Sounds Team 18 D1 3.13 ft³ sealed · 5.30 ft³ ported
URAL Patriot 18 (2+2) 1.62 ft³ sealed · 5.33 ft³ ported

All 18″ subwoofers in our database →

FAQ

What box does the Soundstream XXX-18 need?

Recommended net volume: 2.28 ft³ sealed, 4.41 ft³ ported tuned to 30 Hz — for one sub in a sedan at 10,000 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.

What are the Soundstream XXX-18 Thiele/Small specs?

Fs 22.3 Hz, Qts 0.18, Vas 5.50 ft³, Xmax 1.38″, Sd 149.1 in².

What is the Soundstream XXX-18 mounting depth?

Mounting depth is 11 1/8″, cutout diameter 16 3/4″. The inside depth of the box must exceed the mounting depth by at least 1″.

How much power does the Soundstream XXX-18 handle and how do I wire it?

RMS power rating: 10,000 W. Wiring for several subs and amp power — in the wiring calculator.

Is the Soundstream XXX-18 better sealed or ported?

EBP 117: a ported box (4.41 ft³, tuned to 30 Hz) suits it best — deeper and louder. Sealed (2.28 ft³) the bass is drier.

What port does the Soundstream XXX-18 need?

For the 4.41 ft³ ported box tuned to 30 Hz: slot 4 5/16 × 19 7/16″, 49 1/16″ long, area 84.2 in²; or a round port Ø10 3/8″, ≈ 49 1/16″ long. Port air speed at 10,000 W: 142 ft/s.

What box do two Soundstream XXX-18 subs need?

Two subs need twice the volume: 4.56 ft³ sealed, or 8.83 ft³ ported at the same 30 Hz tuning with twice the port area. One shared chamber or one per sub — whatever fits your vehicle.