Fi Audio TEAM 18 D1

18″ subwoofer · dual 1 Ω · 4,000 W RMS

31.7 HzFs, resonance

0.43Qts

3.37 ft³Vas

1.30″Xmax

4,000 WRMS

Source	web.archive.org · 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, 4,000 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

2.30 ft³ (65 L)

Net volume

Bass character (Qtc)	Flat and accurate · 0.68
Fc	50 Hz
F3 (−3 dB, no cabin gain)	55 Hz
Example box (outside)	20 1/16″ × 20 1/16″ × 14 3/16″

Open sealed box in designer

Ported

deeper, louder

3.00 ft³ (85 L)

Net volume

Tuning (Fb)	34 Hz
Port	slot 4 1/8 × 19 7/16″, 54 1/2″ long
Port velocity at 4,000 W	69 ft/s
F3 (−3 dB, no cabin gain)	33 Hz
Example box (outside)	31 1/2″ × 20 7/8″ × 19 9/16″

Open ported box in designer

Deeper: 4.48 ft³ (127 L) tuned to 31 Hz, 31 1/2″ × 20 7/8″ × 27 1/16″ 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	dual 1 Ω
RMS power	4,000 W
Fs	31.7 Hz
Qts	0.43
Qes	0.45
Qms	9.91
Vas	3.37 ft³

Re (one coil)	0.75 Ω
Sd	187.6 in²
Xmax	1.30″
Vd	243.7 in³ calc.
Mms	548 g calc.
BL	13.5 T·m calc.
EBP	70 — sealed or ported calc.
Sensitivity, 1 W / 1 m	90.3 dB calc.

Mounting dimensions

Cutout diameter	16 3/4″
Mounting depth	11 3/4″
Overall diameter	18 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/20151202050949/http://www.ficaraudio.com:80/product/team-ser

Other Fi Audio 18″ models

Fi Audio BL-NEO 18 D1 18″ · dual 1 Ω
Fi Audio BL-NEO 18 D2 18″ · dual 2 Ω
Fi Audio BL18v3 D1 18″ · dual 1 Ω
Fi Audio BL18v3 D2 18″ · dual 2 Ω
Fi Audio BL18v3.1 D1 18″ · dual 1 Ω
Fi Audio BL18v3.1 D2 18″ · dual 2 Ω
Fi Audio BTL-NEO18 D1 18″ · dual 1 Ω
Fi Audio BTL-NEO18 D2 18″ · dual 2 Ω
Fi Audio BTL3 18 D1 18″ · dual 1 Ω
Fi Audio BTL3 18 D2 18″ · dual 2 Ω
Fi Audio BTL4 18 D1 18″ · dual 1 Ω
Fi Audio BTL4 18 D2 18″ · dual 2 Ω

Similar 18″ subwoofers from other brands

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

Audioque HDC318-A D1 1.70 ft³ sealed · 3.07 ft³ ported
Sundown Audio NSv4-18 D1 2.86 ft³ sealed · 5.23 ft³ ported
Ascendant Audio TEAM 18 D2 2.30 ft³ sealed · 5.54 ft³ ported
Ascendant Audio TEAM 18 D1 2.30 ft³ sealed · 5.54 ft³ ported
Sundown Audio SAv2-18 D4 1.87 ft³ sealed · 4.52 ft³ ported
Sundown Audio NSv5-18 D1 1.62 ft³ sealed · 2.83 ft³ ported

FAQ

What box does the Fi Audio TEAM 18 D1 need?

Recommended net volume: 2.30 ft³ sealed, 3.00 ft³ ported tuned to 34 Hz — for one sub in a sedan at 4,000 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.

What are the Fi Audio TEAM 18 D1 Thiele/Small specs?

Fs 31.7 Hz, Qts 0.43, Vas 3.37 ft³, Xmax 1.30″, Sd 187.6 in².

What is the Fi Audio TEAM 18 D1 mounting depth?

Mounting depth is 11 3/4″, 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 Fi Audio TEAM 18 D1 handle and how do I wire it?

RMS power rating: 4,000 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.