Sony XS-GTX121L
12″ subwoofer · 4 Ω · 300 W RMS
The Sony XS-GTX121L is a 12″ subwoofer. With Qts 0.43 and EBP 57 it works both sealed and ported: sealed is tighter and smaller, ported is deeper and louder. Modest excursion (Xmax 0.19″) — for clean sound at moderate levels, not for SPL competitions.
| Source | sony.com, sony.co.uk · manufacturer data |
|---|---|
| Checked against source | October 2026 |
| Thiele/Small parameters | complete |
| Mounting dimensions | 0 of 4 — missing: cutout, mounting depth, frame outer diameter, magnet diameter; the designer will use an estimate |
- Fs, Vas and Sd don't match the moving mass of 157 g (they give 197 g) — one of the spec sheet values is probably wrong.
Recommended box
For a sedan, one sub, 300 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| Bass character (Qtc) | Tight and punchy · 0.80 |
|---|---|
| Fc | 51 Hz |
| F3 (−3 dB, no cabin gain) | 48 Hz |
| Example box (outside) | 14 3/16″ × 14 3/16″ × 11 9/16″ |
Ported
deeper, louder| Tuning (Fb) | 30 Hz |
|---|---|
| Port | slot 1 9/16 × 14 5/16″, 36 7/16″ long |
| Port velocity at 300 W | 44 ft/s |
| F3 (−3 dB, no cabin gain) | 30 Hz |
| Example box (outside) | 31 1/2″ × 15 3/4″ × 11 1/8″ |
Deeper: 2.83 ft³ (80 L) tuned to 27 Hz, 31 1/2″ × 15 3/4″ × 15″ outside — a bigger box with flatter deep bass. Open in the calculator
Projects with this subwoofer
Boxes that users designed and published: plans, cut sheet and response graph.
Thiele/Small parameters
| Size | 12″ |
|---|---|
| Voice coils | 4 Ω |
| RMS power | 300 W |
| Fs | 27.5 Hz |
| Qts | 0.43 |
| Qes | 0.479 |
| Qms | 4.67 |
| Vas | 2.05 ft³ |
| Re | 3.43 Ω |
|---|---|
| Sd | 76.1 in² |
| Xmax | 0.19″ |
| Vd | 14.1 in³ calc. |
| Mms | 197 g calc. |
| BL | 15.6 T·m calc. |
| EBP | 57 — sealed or ported calc. |
| Sensitivity, 1 W / 1 m | 86 dB calc. |
Mounting dimensions
| Cutout diameter | ≈ 11 1/8″ |
|---|---|
| Mounting depth | ≈ 5 7/8″ |
Where it fits in a vehicle
Spots from our vehicle guides where the cutout, mounting depth and recommended box fit. The spot sizes are approximate — measure your own vehicle.
- Bronco 4-door — behind the rear seat sealed and ported box
- Wrangler 4-door, hard top — behind the rear seat sealed and ported box
- Wrangler 4-door, soft top — behind the rear seat sealed and ported box
- Silverado / Sierra Crew Cab — under the rear seat sealed and ported box
- FJ Cruiser — behind the rear seat sealed and ported box
- El Camino 1978–87 — behind the seat sealed and ported box
- Cherokee XJ — cargo area, spare moved out sealed and ported box
- Excursion — behind the third row sealed and ported box
- Mustang 2015–2023 coupe — trunk sealed and ported box
- Challenger / Charger — trunk sealed and ported box
- Club Car Precedent — under the rear seat sealed box
“≈” 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
- sony.com/electronics/support/res/manuals/4290/42904362M.pdf
- sony.co.uk/electronics/support/car-marine-entertainment-in-car-speakers/xs-gtx12
Other Sony 12″ models
- Sony XS-GSW121D 12″ · dual 4 Ω
- Sony XS-GTR120L 12″ · 4 Ω
- Sony XS-GTR121L 12″ · 4 Ω
- Sony XS-GTX120L 12″ · 4 Ω
- Sony XS-L12S 12″ · 4 Ω
- Sony XS-W122ES 12″ · 2 Ω
- Sony XS-W124ES 12″ · 4 Ω
Similar 12″ subwoofers from other brands
Close in Fs, Qts and Vas — a box of similar volume will suit them.
- Crossfire C312D2-V3 0.88 ft³ sealed · 1.66 ft³ ported
- Earthquake Subzero 12 0.81 ft³ sealed · 1.62 ft³ ported
- Alpine S2-W12D2 0.78 ft³ sealed · 1.45 ft³ ported
- JBL GTO1214 1.06 ft³ sealed · 1.66 ft³ ported
- Resilient Sounds Gold 12 D4 0.88 ft³ sealed · 1.55 ft³ ported
- Infinity Kappa 120.9W 0.92 ft³ sealed · 1.55 ft³ ported
FAQ
What box does the Sony XS-GTX121L need?
Recommended net volume: 0.85 ft³ sealed, 1.66 ft³ ported tuned to 30 Hz — for one sub in a sedan at 300 W. Fit the box to your space and amp in the free calculator, with plans and a cut sheet.
What are the Sony XS-GTX121L Thiele/Small specs?
Fs 27.5 Hz, Qts 0.43, Vas 2.05 ft³, Xmax 0.19″, Sd 76.1 in².
How much power does the Sony XS-GTX121L handle and how do I wire it?
RMS power rating: 300 W. Wiring for several subs and amp power — in the wiring calculator.
Is the Sony XS-GTX121L better sealed or ported?
EBP 57: both work — sealed 0.85 ft³ is tighter and smaller, ported 1.66 ft³ tuned to 30 Hz is deeper and louder.
What port does the Sony XS-GTX121L need?
For the 1.66 ft³ ported box tuned to 30 Hz: slot 1 9/16 × 14 5/16″, 36 7/16″ long, area 22.6 in²; or a round port Ø5 3/8″, ≈ 36 7/16″ long. Port air speed at 300 W: 44 ft/s.
What box do two Sony XS-GTX121L subs need?
Two subs need twice the volume: 1.70 ft³ sealed, or 3.32 ft³ ported at the same 30 Hz tuning with twice the port area. One shared chamber or one per sub — whatever fits your vehicle.