Proline X
Performance Optimized Down Fire Wide Sealed 10" Enclosure | JL Audio 10W3v3
SKU: PO 10-S DFW W3
- Alignment: 1.156 cu ft net, Qtc 0.683, Fc 44.4 Hz, F3 46.0 Hz. Volume set by driver clearance, better damped than JL's 0.625 spec
- Down Fire Wide: 41"W x 12"D x 7.4375"H, 3" shallower than the standard 30 x 15 W3v3 cabinet, for under rear seats. Installed height 9.1875" on the 1.75" standoffs
- Driver: JL Audio 10W3v3-4 (SVC 4Ω), 500W RMS, 14.0mm Xmax, 5.93" mounting depth
- Build: Proline X V-groove and dado joinery, double-layer 1.5" front baffle with flush outer recess, windowed U-brace, 12g OFC side-mounted terminal cup
Financing available. Choose Shop Pay Installments at checkout.
Performance Optimized Down Fire Wide Sealed 10" Enclosure | JL Audio 10W3v3
More enclosures cut for JL Audio subwoofers: JL Audio Subwoofer Boxes
Proline X Performance Optimized Down Fire Wide 10" Sealed
Under rear seat fitment for trucks and SUVs. Cut for the JL Audio 10W3v3-4
The Down Fire Wide Format
Down Fire Wide is the Performance Optimized answer to a specific problem: the space under the rear seat of a truck or SUV, or a narrow cargo floor, is long and shallow, and a 30 by 15 inch Down Fire cabinet will not go in it.
So the cabinet is turned sideways. This one runs 41 inches wide by 12 inches deep by 7.4375 inches tall. It is the same 10W3v3-4, in a cabinet 3 inches shallower front to back than our standard 30 by 15 inch 10W3v3-4 cabinet and 11 inches longer. The airspace given up in depth is recovered along the length, so the driver still gets a properly sized chamber rather than a compromised one.
Which one to choose. If you have 15 inches of depth, the standard 30 by 15 inch cabinet is the pick: it is shorter end to end and stands 7.5625 inches tall. If depth stops at 12 inches and you have 41 inches of run, this is the cabinet that fits. Measure the depth first. Under seat spaces vary widely between cab configurations, and depth is almost always the limiting dimension.
Performance, Performance Optimized, and Micro
Proline X builds three tiers of Down Fire enclosure. The difference is not finish or materials, it is whether the cabinet was designed for a category or for a driver, and how much of the fitting work is already done for you.
| Performance | Performance Optimized | Micro Series | |
|---|---|---|---|
| Fitment | Universal. Accepts any subwoofer that clears the published cutout and mounting depth. | Woofer specific. Cut for one named subwoofer, with cutout, mounting depth, magnet clearance and displacement drawn in CAD from that driver. | Woofer specific. Cut for one named subwoofer. |
| Footprint | Sized to the driver diameter. 24.5 by 13.5 inches on the 10 inch. | Shared 30 by 15 inch platform on most builds. Down Fire Wide variants like this one run long and shallow for under seat fitment. | Compact per driver footprint. 21.5 by 14.5 inches on the 10 inch. |
| Front baffle | Single, 3/4 inch. | Double layer, outer layer machined as a flush recess. 1.5 inch. | Double, 1.5 inch. |
| Driver mounting | Solid flange. You drill your own mounting holes. | 8/32 threaded inserts, stainless machine screws included. | 8/32 threaded inserts, stainless machine screws included. |
| Joinery | V-groove and dado, CNC cut. | V-groove and dado, CNC cut, perimeter cross brace. | Stack fab, dowel reinforced. |
| Published alignment | Modeled Qtc profiles across a range of drivers. No single response curve. | A real predicted Qtc and F3 for that exact driver, calculated from its own Thiele-Small parameters. | Target alignment described in the listing. |
| Carpet | Gray standard, black optional. | Plush black. | Plush black. |
| Warranty | 1 year limited. | 1 year limited. | 2 years. |
Feet ship with every tier, uninstalled on purpose. Mount them where your floor wants them for a down fire install, or leave them off and run the cabinet front firing or up firing. The orientation is yours to choose.
This page is a Performance Optimized enclosure. The cutouts, the cabinet height and the chamber volumes all come from the JL Audio 10W3v3-4's own published numbers. A Performance box fits your subwoofer. A Performance Optimized box was built for it.
Built Around the 10W3v3-4
Nothing about this cabinet is generic. The baffle is bored to the 10W3v3-4's 9.0625 inch cutout, 230mm, and the cabinet height is set by the driver's 5.93 inch mounting depth, 151mm, which is deep for this program. The 10W3v3-4 is a conventional deep motor driver rather than a shallow, so the cabinet is built around clearing it rather than around a target volume.
It is a single 4-ohm voice coil subwoofer rated 500 watts RMS with a recommended amplifier range of 150 to 500 watts. Mineral-filled polypropylene cone, rubber surround, 14.0mm of one-way linear excursion, and 53.475 square inches of piston area. JL Audio's Dynamic Motor Analysis handles motor linearity, and Elevated Frame Cooling routes air through slots above the top plate directly onto the voice coil.
Published Thiele-Small parameters are Fs 31.49 Hz, Qts 0.485, and Vas of 32.23 liters, with Qes 0.523 and Qms 7.017. Sensitivity is 84.87 dB at 1 watt.
Net Volume, Not Gross
The cabinet measures 1.214 cubic feet gross and 1.156 cubic feet net after the driver's published 0.049 cubic feet of displacement and the brace are subtracted. That is larger than the 0.625 cubic foot box JL Audio recommends, and the reason is fitment rather than preference.
True net, not marketing net. Internal volume is calculated from the machined cavity dimensions and the driver's published displacement, not estimated from external dimensions minus wall thickness.
Height on this cabinet is set by the driver's mounting depth, not by a volume target. The 5.93 inch driver reaches 4.43 inches past the inner baffle into the cabinet, and we hold 0.75 inch of clearance above the motor. That fixes the cabinet at 7.4375 inches tall, and on a 41 by 12 footprint that height holds 1.156 cubic feet net, more than the 1.09 cubic feet the standard cabinet was built to. More air in a sealed box lowers Qtc, which is the safe direction: slightly more damping and a gentler approach to the rolloff.
The constraint improves the result. At 1.156 cubic feet net the system sits at Qtc 0.683, Fc 44.4 Hz, F3 46.0 Hz, just under the 0.707 maximally flat reference: flat anechoic response to the corner, clean transient behavior with no overhang, and a gentle 12 dB per octave rolloff that integrates naturally with rising cabin gain below 60 Hz. Sealed Qtc always falls as the box grows, and the fitment requirement pushed this one onto a textbook alignment.
Down Fire Wide Construction
Cut with V-groove and dado joinery on our ShopSabre routers from Langboard Elite 3/4 inch MDF, a dense 48.5 lb/ft³ board with a 200 psi internal bond and 410,000 psi MOE. Every panel joint is a machined interlocking groove that mechanically locks before adhesive is applied, which keeps the cabinet airtight under sustained pressure cycling. Corners are square on Down Fire cabinets.
The cabinet measures 41 inches wide by 12 inches deep by 7.4375 inches tall, measured in the down fire position and excluding standoffs. The 1.75 inch standoffs ship uninstalled so you can place them to suit your floor; installed, the finished stack is 9.1875 inches. Plan the space around that figure, not the cabinet height.
1.5 Inch Double Baffle
Two 3/4 inch layers laminated to 1.5 inches, with the outer layer machined as a flush recess so the driver bolts to the inner layer. The driver lands on 8/32 threaded inserts, with stainless machine screws included. The 10W3v3-4's 10.5 inch frame sits on the 12 inch deep baffle.
Windowed U-Brace
A windowed U-brace dadoed to the shell ties the front and rear walls together across the 41 inch span, and polyfill is installed as a light wall lining.
Side-Mounted Terminal Cup
Proline X ABS and carbon fiber composite cup with stainless hardware and copper ring terminals, pre-wired in 12 gauge OFC. Side mounted so it stays accessible with the baffle facing the floor.
Standoffs Included
1.75 inch standoffs ship with the enclosure, uninstalled. Mount them for a down fire install, or leave them off and run the cabinet front firing or up firing.
Power and Wiring
JL Audio rates the 10W3v3-4 at 500 watts RMS continuous and recommends 150 to 500 watts of amplifier power. Run the top of that range. Sensitivity is 84.87 dB at 1 watt, and Elevated Frame Cooling is what keeps the coil in shape when you do.
Wiring is straightforward: a single voice coil at 4 ohms nominal, so there is no series or parallel decision at the driver and the amplifier simply sees 4 ohms through the side-mounted cup. Confirm your amplifier is comfortable at that load before setting gain.
Bring your own JL Audio 10W3v3-4; the driver is purchased separately. The enclosure carries a 1 year limited warranty.
Cut for the Driver, Not the Catalog
Down Fire Wide, built for the space under a rear bench, one at a time in Tullahoma, Tennessee. Questions on fitment or amplifier matching, call 931-563-5151.
| Series | Proline X Performance Optimized Down Fire Wide |
| Enclosure Type | Sealed | Down Fire Geometry | Floor-Coupled |
| Intended Fitment | Under The Rear Seat Of Trucks And SUVs, Or Narrow Cargo Floors, Where Depth Is The Limiting Dimension |
| Driver-Specific Fitment | JL Audio 10W3v3-4 (SVC 4Ω) |
| Internal Volume (Gross) | 1.214 Cubic Feet |
| Internal Volume (Net After Displacement) | 1.156 Cubic Feet |
| JL Audio Recommended Sealed Volume | 0.625 Cubic Feet (This Cabinet Is Larger Because Driver Clearance Sets Its Height) |
| Target System Qtc | 0.683 (Just Under Textbook Maximally Flat) |
| Predicted Fc | 44.4 Hz |
| Predicted F3 | 46.0 Hz |
| Comparison, Standard 30x15 W3v3 | 30 x 15 x 7.5625 Inches, 1.09 Cubic Feet Net. The Wide Cabinet Holds More Air At Its Clearance-Set Height |
| Driver Fs | 31.49 Hz |
| Driver Qts | 0.485 |
| Driver Qes / Qms | 0.523 / 7.017 |
| Driver Vas | 1.138 Cubic Feet / 32.23 Liters |
| Driver Sd | 53.475 sq in / 0.0345 m² |
| Driver Xmax (One-Way Linear) | 14.0mm / 0.550 in |
| Driver Displacement | 0.049 Cubic Feet / 1.39 L (Published by JL Audio) |
| Driver Sensitivity | 84.87 dB (1W/1m) |
| Driver Power Handling | 500 Watts RMS Continuous |
| Recommended Amplifier Power | 150 to 500 Watts RMS (JL Audio Spec) |
| Driver Cone | Mineral-Filled Polypropylene | Rubber Surround |
| Driver Technology | Dynamic Motor Analysis (DMA) | Elevated Frame Cooling |
| Mounting Depth Required | 5.93 Inches / 151mm (JL Audio Spec) |
| Cutout Diameter | 9.0625 Inches / 230mm (JL Audio Spec) |
| Driver Overall Diameter | 10.5 Inches / 267mm (JL Audio Spec) |
| Baffle Configuration | Down Firing - Driver Fires Toward Floor |
| Material | Langboard Elite 3/4" MDF |
| Front Baffle Construction | Double-Layer 1.5" MDF | Outer Layer Flush Recess, Driver Mounts To Inner Layer |
| Motor Clearance | 0.76 Inch Above The Motor (0.75 Minimum) |
| Joinery | V-Groove and Dado (CNC-Cut) |
| Corner Profile | Square (Down Fire Series Standard) |
| Standoffs | 1.75 Inch, Included, Shipped Uninstalled |
| Construction | ShopSabre CNC / Windowed U-Brace |
| External Width | 41 Inches |
| External Depth | 12 Inches |
| External Height | 7.4375 Inches |
| Dimension Reference | All External Dimensions Measured In Down Fire Position, Excluding Standoffs |
| Installed Height | 9.1875 Inches With The 1.75 Inch Standoffs |
| Voice Coil Configuration | Single Voice Coil | 4 Ohm Nominal |
| Mounting Hardware | 8/32 Threaded Inserts | Stainless Steel Machine Screws Included |
| Terminal Cup | Proline X ABS/Carbon Fiber Composite | Side Mounted | 12g OFC Pre-Wired |
| Damping | Polyfill Pre-Installed As A Light Wall Lining |
| Carpet Finish | Plush Black |
| Bundle Options | Enclosure Only (Bring Your Own JL Audio 10W3v3-4) |
| Warranty | 1-Year Limited (Enclosure) |
| Manufactured | Tullahoma, Tennessee, USA |
01Is it a sealed driver?
Efficiency bandwidth product places the motor before anything else is decided.
02What the box does to it
1.156 cu ft against a 32.2 L Vas.
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 14.0 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.
| Param | Value | Unit | Note |
|---|---|---|---|
| Fs | 31.49 | Hz | free-air resonance |
| Qts | 0.485 | 4 | |
| Vas | 32.23 | L | equivalent compliance |
| Sd | 345.0 | cm² | effective piston area |
| Xmax | 14 | mm | one-way linear travel |
| Pe | 500 | W | continuous RMS |
| SPL | 84.7 | dB | 1 W / 1 m, derived from T/S |
Driver parameters as published by jlaudio.com. Curves computed against this enclosure’s actual net airspace.
Built From a Spec Sheet, Not a Sales Sheet
Every Proline X Performance Series enclosure is CNC-cut from Langboard Elite MDF, 3/4" (18mm) panels produced to published mill specifications. Most enclosure manufacturers source generic MDF without published data. We can tell you the internal bond rating, the modulus of elasticity, the modulus of rupture, and the face and edge screw holding strength for every panel in this enclosure, because we chose the material based on those numbers, not on price or availability.
Langboard Elite is produced in the United States. The specifications below are pulled directly from Langboard's published mill data and are verifiable. This is the same panel stock used in our full Proline X lineup.
Langboard Elite MDF: Published Mill Data
| Property | Value | Why It Matters |
|---|---|---|
| Panel Stock | Langboard Elite MDF | Named, verifiable panel source, not generic "high-density MDF" |
| Thickness | 3/4" (18mm) | Industry standard for subwoofer enclosures; panels below this flex under pressure |
| Density | 48.5 lbs/ft³ | Higher density = less porosity, better screw retention, reduced resonance |
| Internal Bond | 200 psi | Measures resistance to delamination under sustained internal pressure. The most enclosure-relevant spec on this sheet |
| Modulus of Rupture (MOR) | 4,200 psi | Bending strength before the panel breaks, relevant for larger unsupported baffle spans |
| Modulus of Elasticity (MOE) | 410,000 psi | Stiffness under load; higher MOE means less panel flex under bass pressure, less resonance |
| Face Screw Holding | 325 lbs | How firmly the panel surface holds a screw; critical for baffle joint integrity over time |
| Edge Screw Holding | 250 lbs | Panel edge retention, relevant for every joint that isn't face-to-face |
200 psi: The Number That Actually Matters for Enclosures
The internal bond rating measures how well the MDF panel resists delamination under sustained pressure applied perpendicular to the face. In a subwoofer enclosure, every bass transient generates a pressure pulse that pushes outward on every panel simultaneously. A panel that begins to delaminate internally loses stiffness gradually. The symptoms are slow: a box that starts to sound softer, less defined, less punchy over months of use. 200 psi internal bond is the spec that determines how long this enclosure holds its acoustic integrity under daily use at real power levels.
410,000 psi MOE: Less Flex, Less Resonance
The modulus of elasticity measures panel stiffness, its resistance to bending under load. A stiffer panel flexes less under the pressure generated by a high-excursion driver at volume. Panel flex is a source of acoustic coloration: the panel itself begins to radiate sound at its own resonant frequency, adding distortion to the output. 410,000 psi stiffness combined with V-groove and dado joinery means the panels stay rigid and the bracing controls resonance at the structure level, not the panel level. The bass you hear comes from the driver, not the box.
325 lb Face / 250 lb Edge: Joints That Stay Locked
Screw holding strength determines how firmly the panel grips a fastener at the face and at the edge. This matters most at the baffle joint, where the front panel meets the side panels and where the driver is mounted. A panel with low screw holding strength allows fasteners to loosen over time under vibration, leading to air gaps at the joint and loss of acoustic seal. 325 lb face screw holding strength means the baffle hardware stays put. Combined with dado joinery and adhesive, the front panel on a Proline X Performance Series enclosure is not going anywhere.
Named Panel Stock: Not "Premium MDF"
The phrase "premium MDF" or "high-density MDF" appears on marketing copy for enclosures across every price point, from $40 to $400. It is not a specification. It is a description with no defined standard. Langboard Elite is a named, sourced, mill-documented product with published data. We name it in our copy because naming it holds us accountable to the spec. You can look up Langboard Elite independently, verify the numbers on this page, and confirm you are getting what we say you are getting. That is the point.
Why Proline X?
Most enclosures are built to a price point. Proline X is built to a spec. Every box starts with published-data MDF, gets CNC-cut to exact internal volume, and is assembled by hand in our Tennessee facility. The difference shows up in the measurements, and in how the box holds up two years into daily use.
CNC-Cut to Spec
Panels are machine-cut on ShopSabre CNC routers and joined with V-groove and dado joinery. Consistent geometry, no hand-cut variance, no gaps at the joints.
Handcrafted in USA
Hand-assembled at our facility in Tullahoma, TN. Every enclosure is inspected before it ships.
Tuned to the Build
Internal volume and port geometry are calculated to spec and CNC-cut to exact dimensions. The box performs the same way every time.
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