Soundstream USA8

8″ subwoofer · dual 4 Ω · 150 W RMS

48 HzFs, resonance

0.58Qts

0.71 ft³Vas

0.14″Xmax

150 WRMS

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:

The spec sheet's Qts 0.64 doesn't match its Qes and Qms (they give 0.58).

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

smaller, tighter

0.78 ft³ (22 L)

Net volume

Bass character (Qtc)	Tight and punchy · 0.80
Fc	66 Hz
F3 (−3 dB, no cabin gain)	62 Hz
Example box (outside)	10 1/4″ × 10 1/4″ × 19 7/16″

Open sealed box in designer

Ported

deeper, louder

0.57 ft³ (16 L)

Net volume

Tuning (Fb)	41 Hz
Port	slot 1 15/16 × 14 5/16″, 75″ long
Port velocity at 150 W	15 ft/s
F3 (−3 dB, no cabin gain)	50 Hz
Example box (outside)	31 1/2″ × 15 3/4″ × 9 9/16″

The volume and tuning are the recommendation, but the port doesn’t fit this example box. Size the box and port in the designer.

Open ported box in designer

Deeper: 1.31 ft³ (37 L) tuned to 43 Hz, 31 1/2″ × 15 3/4″ × 8 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	8″
Voice coils	dual 4 Ω
RMS power	150 W
Fs	48 Hz
Qts	0.58
Qes	0.61
Qms	11.9
Vas	0.71 ft³

Re (one coil)	2.68 Ω
Sd	34.1 in²
Xmax	0.14″
Vd	4.7 in³ calc.
Mms	38 g calc.
BL	7.1 T·m calc.
EBP	79 — sealed or ported calc.
Sensitivity, 1 W / 1 m	87.6 dB calc.

Mounting dimensions

Cutout diameter	7 1/8″
Mounting depth	3 1/2″

“≈” 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/20060911083113/http://www.soundstream.com:80/manuals/sbw/usa

Other Soundstream 8″ models

Soundstream EXACT 8 8″ · 4 Ω
Soundstream R3.8 8″ · dual 2 Ω

Similar 8″ subwoofers from other brands

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

Polk Audio EX8 (EX Series II) 0.57 ft³ sealed · 0.53 ft³ ported
Polk Audio MM2084 DVC 0.78 ft³ sealed · 0.57 ft³ ported
Polk Audio db840DVC 0.67 ft³ sealed · 0.57 ft³ ported
Polk Audio DXi804 DVC 0.67 ft³ sealed · 0.57 ft³ ported
Dayton Audio PCS8-4 0.42 ft³ sealed · 0.57 ft³ ported
Polk Audio MM840DVC 0.53 ft³ sealed · 0.57 ft³ ported

FAQ

What box does the Soundstream USA8 need?

Recommended net volume: 0.78 ft³ sealed, 0.57 ft³ ported tuned to 41 Hz — for one sub in a sedan at 150 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.

What are the Soundstream USA8 Thiele/Small specs?

Fs 48 Hz, Qts 0.58, Vas 0.71 ft³, Xmax 0.14″, Sd 34.1 in².

What is the Soundstream USA8 mounting depth?

Mounting depth is 3 1/2″, cutout diameter 7 1/8″. The inside depth of the box must exceed the mounting depth by at least 1″.

How much power does the Soundstream USA8 handle and how do I wire it?

RMS power rating: 150 W. Dual 4 Ω voice coils: series gives 8 Ω, parallel gives 2 Ω at the amp. Wiring for several subs and amp power — in the wiring calculator.