Fi Audio Xv5 8 D1

8″ subwoofer · dual 1 Ω · 500 W RMS

38 HzFs, resonance

0.61Qts

0.26 ft³Vas

0.63″Xmax

500 WRMS

Source	ficaraudio.com · manufacturer data
Checked against source	October 2026
Thiele/Small parameters	complete
Mounting dimensions	3 of 4 — missing: magnet diameter; the designer will use an estimate

Recommended box

For a sedan, one sub, 500 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

0.35 ft³ (10 L)

Net volume

Bass character (Qtc)	Tight and punchy · 0.81
Fc	50 Hz
F3 (−3 dB, no cabin gain)	46 Hz
Example box (outside)	10 5/8″ × 10 5/8″ × 9 5/16″

Open sealed box in designer

Ported

deeper, louder

0.49 ft³ (14 L)

Net volume

Tuning (Fb)	41 Hz
Port	slot 1 15/16 × 14 5/16″, 86 3/8″ long
Port velocity at 500 W	32 ft/s
F3 (−3 dB, no cabin gain)	35 Hz
Example box (outside)	31 1/2″ × 15 3/4″ × 10 1/16″

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: 0.95 ft³ (27 L) tuned to 32 Hz, 19 5/8″ × 15 3/4″ × 8 11/16″ 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 1 Ω
RMS power	500 W
Fs	38 Hz
Qts	0.61
Qes	0.71
Qms	4.45
Vas	0.26 ft³

Re (one coil)	1.06 Ω
Sd	30.7 in²
Xmax	0.63″
Vd	19.3 in³ calc.
Mms	133 g calc.
BL	6.9 T·m calc.
EBP	54 — sealed or ported calc.
Sensitivity, 1 W / 1 m	79.5 dB calc.

Mounting dimensions

Cutout diameter	7 1/2″
Mounting depth	6 3/16″
Overall diameter	8 11/16″

Judging by its value, the published Re is for both coils in series — converted to per coil.

“≈” 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

ficaraudio.com/xv5-series-8/

Other Fi Audio 8″ models

Fi Audio Xv5 8 D2 8″ · dual 2 Ω

Similar 8″ subwoofers from other brands

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

DC Audio M3 8 D4 0.32 ft³ sealed · 0.49 ft³ ported
Sky High Car Audio BMX-8 D2 0.35 ft³ sealed · 0.46 ft³ ported
DL Audio Barracuda 8 Flat (2+2) 0.53 ft³ sealed · 0.53 ft³ ported
Cadence S2W8D2 0.32 ft³ sealed · 0.53 ft³ ported
Sundown Audio Ev5-8 D4 0.28 ft³ sealed · 0.49 ft³ ported
Quantum Audio QW3000/8D4 0.28 ft³ sealed · 0.53 ft³ ported

FAQ

What box does the Fi Audio Xv5 8 D1 need?

Recommended net volume: 0.35 ft³ sealed, 0.49 ft³ ported tuned to 41 Hz — for one sub in a sedan at 500 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.

What are the Fi Audio Xv5 8 D1 Thiele/Small specs?

Fs 38 Hz, Qts 0.61, Vas 0.26 ft³, Xmax 0.63″, Sd 30.7 in².

What is the Fi Audio Xv5 8 D1 mounting depth?

Mounting depth is 6 3/16″, cutout diameter 7 1/2″. The inside depth of the box must exceed the mounting depth by at least 1″.

How much power does the Fi Audio Xv5 8 D1 handle and how do I wire it?

RMS power rating: 500 W. Dual 1 Ω voice coils: series gives 2 Ω, parallel gives 0.5 Ω at the amp. Wiring for several subs and amp power — in the wiring calculator.