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Proline X PO 12-S DFW TW3 sealed down-fire wide enclosure for the JL Audio 12TW3, 41 inches wide by 5.5 inches tall, feet add 1.75 inches of height.
Proline X PO 12-S DFW TW3 sealed down-fire wide enclosure, end panel with side-mounted terminal cup, 5.5 inches tall by 14 inches deep.

Performance Optimized · Datasheet

Performance Optimized Down Fire Wide Sealed 12" Shallow Sub Enclosure JL Audio 12TW3 · Single 12" Sealed enclosure

Net volume
0.869 cu ft after the brace and 0.029 cu ft displacement
Max mounting depth
3.50 Inches (JL Audio Spec)
Cutout
11.625 Inches (JL Audio Spec)
External dimensions
41 in W × 5.5 in in the down fire position H × 14 in D
Front baffle
1.5 in double baffle, outer layer machined as a flush recess
Buy at Audio IntensityFactory-direct, ships from Tullahoma
JL Audio 12TW3Buy at Audio Intensity
  • Alignment: 0.869 cu ft net. Qtc 0.917, Fc 45.7 Hz, F3 37.5 Hz
  • Down Fire Wide: 41"W x 14"D x 5.5"H in down fire position, excludes standoffs, square corners
  • Versus the standard 30 x 15: 6.4375 in tall and 0.862 cu ft net there, 5.5 in tall and 0.869 cu ft net here
  • Driver: JL Audio 12TW3-D4 (DVC 4Ω), 400W RMS, 15.2mm Xmax, 3.50" mounting depth, 13.2" tab-ear frame
  • Standoffs: Included, 1.75 in, shipped uninstalled. Installed height 7.25 in

Spec of record

Technical specifications

SeriesProline X Performance Optimized Down Fire Wide
Compatible DriverJL Audio 12TW3-D4. Direct fit
Enclosure TypeSealed, down fire, floor coupled
Intended FitmentSpaces where height or depth is the limit and 41 in of run is available
Chamber ConfigurationSingle chamber, windowed U-brace, one side-mounted terminal cup
External Width41 in
External Depth14 in
External Height5.5 in in the down fire position, excludes standoffs
Installed Height7.25 in including the 1.75 in standoffs
Internal Volume, Gross0.91 cu ft
Internal Volume, Net0.869 cu ft after the brace and 0.029 cu ft displacement
Height Set ByAirspace; 1.25 in clearance above the motor
AlignmentQtc 0.917, Fc 45.7 Hz, F3 37.5 Hz anechoic
Comparison, Standard 30 x 156.4375 in tall, 0.862 cu ft net. Wide format is 5.5 in tall with 0.869 cu ft net
Driver Fs26.46 Hz
Driver Qts0.531
Driver Qes / Qms0.558 / 10.766
Driver Vas48.73 Liters
Driver Re (Series)9.280 Ohm
Driver Sd539 cm²
Driver Xmax (One-Way Linear)15.2mm / 0.60 in
Driver Displacement0.029 Cubic Feet
Driver Sensitivity82 dB (1W/1m)
Driver Power Handling400 Watts RMS / 800 Watts Peak
Driver ConeMica-Injected Polypropylene (MIPP) | Rubber Surround
Driver Dust CapAluminum-Alloy (Heat-Dissipating)
Driver Voice Coil2.5 in | Aluminum
Driver FrameCast Alloy | Tab-Ear Mounting, 13.2 in
Driver TechnologyPatented Thin-Line / Concentric Tube Suspension
Driver OrientationTab ears run along the 41 in length, about 0.4 in of baffle fore and aft
Mounting Depth Required3.50 Inches (JL Audio Spec)
Cutout Diameter11.625 Inches (JL Audio Spec)
Voice Coil ConfigurationDual 4-Ohm | 2Ω Parallel or 8Ω Series At The Driver
Recommended Power200-400 Watts RMS (JL Audio Rated Range)
MaterialLangboard Elite 3/4 in MDF
ConstructionShopSabre CNC, V-groove and dado joinery
Panel Thickness0.75 in
Front Baffle1.5 in double baffle, outer layer machined as a flush recess
Internal BracingWindowed U-brace, dadoed to the shell
Corner ProfileSquare, Down Fire series standard
Driver Mounting8/32 threaded inserts with stainless machine screws
Terminal CupOne Proline X ABS and carbon fiber composite, side mounted, pre-wired 12 gauge OFC
StandoffsIncluded, 1.75 in, shipped uninstalled
DampingLight polyfill wall lining, does not alter acoustic volume
CarpetPlush Black
Bundle OptionsEnclosure only, bring your own JL Audio 12TW3-D4
Warranty1 Year Limited
Built InTullahoma, Tennessee

Modelled response

Performance in this enclosure

Net airspace
0.869
cu ft net
System Qtc
0.92
sealed
Half power
37.5
Hz · F3
Xmax at
678
W RMS · no filter
With 25 Hz subsonic
752
W RMS · +11%
Amplifier
400
W RMS recommended
This enclosure holds 0.869 cu ft net . In it the JL Audio 12TW3-D4 runs a system Qtc of 0.92 with half power at 37.5 Hz, and the cone reaches its 15.2 mm travel limit at 678 W, above the driver’s 400 W thermal rating, so heat stops you before travel does. Run a subsonic filter at 25 Hz and that becomes 752 W — +75 W, or 11 percent more power for the same 15.2 mm of travel.

01Is it a sealed driver?

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

EBP = Fs ÷ Qes = 47.4
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 D4 47.4
D4 · EBP 47.4
EBP under 50 means a motor that wants a sealed load. The 12TW3-D4 sits at 47.4, inside that band, which is why this is a sealed build rather than a ported one.

02What the box does to it

0.869 cu ft against a 48.7 L Vas.

α = Vas ÷ Vb = 1.98  ·  Fc = Fs√(α+1) = 46 Hz  ·  Qtc = 0.92
20 30 50 70 100 150 200 +6 +0 -6 -12 -18 -24 FREQUENCY · Hz LEVEL · dB −3 dB
D4 · Qtc 0.92, Fc 46 Hz, F3 37.5 Hz
The box lifts resonance from 26.5 Hz free-air to 46 Hz and half power lands at 37.5 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 15.2 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.

PXmax = 678 W unfiltered  →  752 W with a 25 Hz subsonic
20 30 50 70 100 150 200 0 4 8 12 16 FREQUENCY · Hz CONE TRAVEL · mm PAST LINEAR TRAVEL · Xmax 15.2 mm 678 W reaches Xmax here
D4 · 678 W, no filterD4 · 752 W with subsonic at 25 Hz, 24 dB/octXmax 15.2 mm one-way
Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 15.2 mm. Unfiltered that is 678 W, reached first at 29 Hz. It sits above the 400 W the driver can take thermally, so the voice coil gives up before the suspension does. 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 752 W before hitting the same 15.2 mm. That is 11 percent more amplifier for the price of one filter setting.
ParamValueUnitNote
Fs26.46Hzfree-air resonance
Qts0.531D4
Vas48.73Lequivalent compliance
Sd539.0cm²effective piston area
Xmax15.2mmone-way linear travel
Pe400Wcontinuous RMS
SPL83.9dB1 W / 1 m, derived from T/S

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

From the shop floor

Installer's take

Same 12TW3-D4 as the standard 30 by 15 box, laid out 41 by 14. One inch shallower, 11 inches longer, and 5.5 inches tall against 6.4375. Measure all three dimensions before choosing between them.

Airspace set the height here, 0.869 cubic feet net, with 1.25 inches clear above the motor.

Alignment is Qtc 0.917 with F3 at 37.5 Hz.

The 13.2 inch tab-ear frame is the fit detail. Ears run along the 41 inch length, about 0.4 inch of baffle fore and aft. 82 dB sensitivity, so run the full 400 watts.

Before you order

Questions

Why is this cabinet 41 inches wide instead of 30?

Because it trades length for depth and height. The standard single Down Fire platform is 30 wide by 15 deep; this one is 14 deep, 1 inch shallower, and runs 41 inches long to put the airspace along the length instead.

That lets it stand 5.5 inches tall against 6.4375 for the standard box. A 12 inch frame needs about 13 inches of baffle, so 14 is as shallow as a 12 can go. If you have 41 inches of run and height or depth is your limit, this is the shape that works.

How does this compare to the standard 30 x 15 12TW3-D4 enclosure?

The standard box is 30 by 15 by 6.4375 inches and holds 0.862 cubic feet net. This one is 41 by 14 by 5.5 inches and holds 0.869 cubic feet net.

Choose the standard box when length is limited. Choose this one when height or depth is the limit and you have 41 inches of run.

What alignment does this enclosure produce?

At 0.869 cubic feet net the result is Qtc 0.917, Fc 45.7 Hz and F3 37.5 Hz, calculated from the driver's own published Thiele-Small parameters.

That is above the 0.707 maximally flat reference, so there is real lift near the corner rather than a textbook flat curve. The figures are anechoic; in a car, cabin gain adds real output below 50 Hz, so in-vehicle response runs deeper.

How much power should I run, and how do I wire it?

JL Audio rates the 12TW3-D4 at 400 watts RMS and recommends 200 to 400 watts; at 82 dB sensitivity, aim for the top of that range.

The coils are dual 4-ohm, so impedance is set at the driver: 2 ohms in parallel, 8 ohms in series. Confirm the load against your amplifier's minimum stable impedance.

How tall is this once the standoffs are on?

The cabinet is 5.5 inches tall measured in the down fire position, excluding standoffs. The standoffs hold 1.75 inches under the baffle, so plan your space around 7.25 inches installed.

The standoffs ship uninstalled, so you can place them to suit your floor, or leave them off and run the cabinet front firing or up firing.

Where is the terminal cup located on a down fire enclosure?

Side mounted. Every Proline X Performance Optimized enclosure uses a side mounted terminal cup regardless of alignment, whether standard, wedge, or down fire. On this cabinet that keeps the connection accessible with the enclosure installed, since the baffle faces the floor. The cup is our Proline X ABS and carbon fiber composite unit with stainless hardware, copper ring terminals, and pre-wired 12 gauge OFC.

How is this enclosure built?

V-groove and dado joinery, CNC cut on ShopSabre routers from Langboard Elite MDF, with square corners as the Down Fire standard. Every panel joint is a machined interlocking groove that locks before adhesive is applied, which keeps the cabinet airtight under sustained pressure cycling.

The 1.5 inch double baffle has its outer layer machined as a flush recess so the driver bolts to the inner layer, and a windowed U-brace stiffens the long panels. Polyfill is installed as a light wall lining; do not add more, since packing a sealed box makes it act larger and moves the alignment. Assembled and inspected in Tullahoma, Tennessee.

Is the JL Audio 12TW3-D4 included with this enclosure?

No. This listing is for the enclosure only. Bring your own JL Audio 12TW3-D4. The cutout and cabinet height are cut direct fit for this driver.

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