Proline Performance Optimized Series PO 12-S W 2XLD subwoofer enclosure, showing a black acrylic front cover with a circular wood-grain insert and dimension markings of 19.77 inches by 15 inches.A performance-optimized subwoofer enclosure shown on a dark blue gradient background with measurement callouts and product details. The enclosure is dark gray/black with a circular speaker port in the center.

Performance Optimized · Datasheet

Performance Optimized Wedge Sealed 12" Enclosure | PowerBass 2XL-1240D Single 12" Sealed enclosure

Net volume
0.75 cu ft
Max mounting depth
5.4000 in required
Cutout
11.0000 in
External dimensions
19.77 in W × 15 in at the seat face H × 12.30 in at the base D
Front baffle
1.5 in, double baffle
Buy at Audio Intensity
  • Best For: PowerBass 2XL-1240D Trunk-Fit Builds
  • Net Volume: 0.75 cu ft (0.89 cu ft Gross)
  • Alignment: Qtc 0.601, fc 51.6 Hz, F3 62.3 Hz
  • Driver Match: 2XL-1240D
  • Impedance: dual 4 ohm coils
  • Construction: Rear-Firing Wedge | V-Groove/Dado | Double 1.5" Baffle | Threaded Inserts

Technical specifications

SpecificationValue
SeriesProline X Performance Optimized Wedge
Compatible DriverPowerBass 2XL-1240D, quantity 1. Direct fit
ConfigurationSingle 12 inch, single chamber sealed wedge
Mounting PositionTrunk or cargo area, tall face against the rear seat back
Firing DirectionRearward into the trunk. Not a down fire design, no feet included
External Width19.77 in
External Height15 in at the seat face
External Depth12.30 in at the base, tapering to 6.84 in at the top
Internal Volume, Gross0.89 cu ft
Internal Volume, Net Acoustic0.75 cu ft
AlignmentQtc 0.601, fc 51.6 Hz, F3 62.3 Hz anechoic
Driver Cutout11.0000 in
Driver Mounting Depth5.4000 in required
Power Handling450 watts RMS
ImpedanceDual 4 ohm voice coils
MaterialLangboard Elite MDF
ConstructionCNC cut, V-groove and dado joinery
Panel Thickness0.75 in
Front Baffle1.5 in, double baffle
Internal BracingWindowed C brace
Driver MountingThreaded inserts at every mounting location, stainless machine screws included
Terminal CupsOne Proline X ABS and carbon fiber composite, side mounted, pre wired 12 gauge OFC
DampingLight polyfill wall lining, does not alter acoustic volume
CarpetPlush black
Weight26.8 lb
Warranty1 Year Limited
Built InTullahoma, Tennessee

Performance in this enclosure

Net airspace
0.75
cu ft per chamber
System Qtc
0.60
sealed
Half power
62.3
Hz · F3
Xmax at
393
W RMS · no filter
With 25 Hz subsonic
566
W RMS · +44%
Amplifier
450
W RMS recommended
This enclosure holds 0.75 cu ft net per chamber. In it the PowerBass 2XL-1240D runs a system Qtc of 0.60 with half power at 62.3 Hz, and the cone reaches its 11.5 mm travel limit at 393 W, below the driver’s 450 W thermal rating, so travel is what stops you here, not heat. Run a subsonic filter at 25 Hz and that becomes 566 W — +174 W, or 44 percent more power for the same 11.5 mm of travel.

01Is it a sealed driver?

Efficiency bandwidth product places the motor before anything else is decided.

EBP = Fs ÷ Qes = 81.5
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 D4 81.5
D4 · EBP 81.5
At 81.5 the 2XL-1240D sits in the transition band, not the sealed band. That is not a mismatch: a transition motor works in either alignment, and sealed buys a smaller box and a gentler roll-off at the cost of some low-end output. Stage 02 shows what this airspace actually does with it.

02What the box does to it

0.75 cu ft against a 47.5 L Vas.

α = Vas ÷ Vb = 2.24  ·  Fc = Fs√(α+1) = 52 Hz  ·  Qtc = 0.60
20 30 50 70 100 150 200 +6 +0 -6 -12 -18 -24 FREQUENCY · Hz LEVEL · dB −3 dB
D4 · Qtc 0.60, Fc 52 Hz, F3 62.3 Hz
The box lifts resonance from 28.7 Hz free-air to 52 Hz and half power lands at 62.3 Hz, anechoic, before any cabin gain.

03The watts that reach Xmax (in this enclosure)

Travel scales with the square root of power, so there is one wattage that puts the cone exactly on 11.5 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.

PXmax = 393 W unfiltered  →  566 W with a 25 Hz subsonic
20 30 50 70 100 150 200 0 4 8 12 FREQUENCY · Hz CONE TRAVEL · mm PAST LINEAR TRAVEL · Xmax 11.5 mm 393 W reaches Xmax here
D4 · 393 W, no filterD4 · 566 W with subsonic at 25 Hz, 24 dB/octXmax 11.5 mm one-way
Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 11.5 mm. Unfiltered that is 393 W, reached first at 20 Hz. It sits under the 450 W the driver can take thermally, so the enclosure sets the ceiling, not the voice coil. The dashed traces are the same driver behind a subsonic filter at 25 Hz, 24 dB/oct: stopping the cone wasting travel below the passband lets it take 566 W before hitting the same 11.5 mm. That is 44 percent more amplifier for the price of one filter setting.
ParamValueUnitNote
Fs28.70Hzfree-air resonance
Qts0.334D4
Vas47.50Lequivalent compliance
Sd510.7cm²effective piston area
Xmax11.5mmone-way linear travel
Pe450Wcontinuous RMS
SPL86.9dB1 W / 1 m, derived from T/S

Driver parameters as published by powerbassusa.com. Curves computed against this enclosure’s actual net airspace.

Installer's take

This one is straightforward. 0.75 cubic feet net is PowerBass's own published sealed airspace for the 2XL-1240D and we cut to it exactly, which lands at Qtc 0.601. PowerBass publishes 0.587 at the same volume, so there is no argument to have about the alignment.

F3 lands at 62.3 Hz anechoic. That is high for a 12 inch, and it is the driver rather than the cabinet: at a Qts of 0.334 the 2XL-1240D is past the knee for sealed loading, so no sealed box gets it much below 61 Hz. Adding volume makes it worse, not better. If you want the deepest sealed 12 inch in this range, the XL-1244 reaches 46.2 Hz.

On impedance: Dual 4 ohm coils give 8 ohms in series or 2 ohms in parallel on a single driver. Two ohms is the usual choice.

Measure the base depth. This cabinet is 12.30 inches deep at the trunk floor, 6.84 at the top, and 19.77 wide. The floor dimension is what decides whether it goes in.

Questions

Will this enclosure fit the 2XL-1240D exactly?

Yes. The baffle is CNC cut to 11.0000 in for the 2XL-1240D's published cutout and the cabinet clears its 5.4000 in mounting depth. Threaded inserts are pressed in at every mounting location so the driver bolts to metal, not to MDF.

Why 0.75 cubic feet net?

It is PowerBass's published sealed recommendation for the 2XL-1240D. In it the driver runs Qtc 0.601 with fc at 51.6 Hz and F3 at 62.3 Hz. PowerBass publishes Qtc 0.587 and F3 62 Hz for the same airspace, so our numbers and theirs agree.

What amplifier power should I run, and what impedance?

The 2XL-1240D is rated 450 watts RMS, so 450 across the driver. Dual 4 ohm coils give 8 ohms in series or 2 ohms in parallel on a single driver. Two ohms is the usual choice. Aim for roughly 315 to 450 watts at the final wired impedance.

How does a wedge enclosure improve the sound in a trunk installation?

The angled seat-side face matches the roughly 20 degree lean of a factory rear seat, so the cabinet sits flat against it instead of leaving a wasted triangle. The vertical trunk-lid-side face carries the driver, firing rearward into the trunk cavity, which acts as an acoustic extension into the cabin.

Why is the front baffle double-layered?

The baffle is two bonded 3/4 inch sheets, 1.5 inches through. A subwoofer pushes as hard against its mounting surface as it does against the air, and a single 3/4 inch panel flexes under that load. With 11.5 mm of one-way travel and 450 watts on tap that matters.

What is the expected low-frequency extension?

F3 lands at 62.3 Hz anechoic. That is high for a 12 inch, and it is the driver rather than the cabinet: at a Qts of 0.334 the 2XL-1240D is past the knee for sealed loading, so no sealed box gets it much below 61 Hz. Adding volume makes it worse, not better. If you want the deepest sealed 12 inch in this range, the XL-1244 reaches 46.2 Hz. Qtc is 0.601, so the rolloff is clean rather than peaked. These figures are anechoic and exclude cabin gain, which in most vehicles adds real output below 40 Hz.

Do I need to add polyfill or damping?

No. Polyfill is already installed as a light wall lining to control internal reflections, and the quantity is chosen so it does not change the acoustic volume. Do not add more. Packing a sealed box with fill makes it behave as though it were larger, which on this driver moves Qtc down and F3 up.

Is the driver included?

No. This is an enclosure only. You receive the cabinet finished in plush black carpet, with threaded inserts at the driver position, stainless machine screws, one side-mounted pre-wired terminal cup and the polyfill lining already installed.

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