Proline X
Performance Optimized Down Fire Wide Sealed Dual 12" Shallow Sub Enclosure | Alpine RSW12
SKU: PO 12D-S DFW RSW
- Alignment: 0.701 cu ft net per chamber. RS-W12D2, dual 2 ohm: Qtc 1.730, Fc 49.4 Hz, F3 33.8 Hz; RS-W12D4, dual 4 ohm: Qtc 1.797, Fc 51.9 Hz, F3 35.4 Hz
- Down Fire Wide: 41"W x 14"D x 7.75"H in down fire position, excludes the 1.75" standoffs (installed height 9.5"). Stands lower than the standard 30 x 15 at 9.4375"
- Height set by: airspace; 3.75" of clearance above the motor
- Chambers: Two fully separate sealed chambers, 3/4" MDF full divider, one shared side-mounted terminal cup
- Driver: Alpine RS-W12D2 (DVC 2 ohm) or RS-W12D4 (DVC 4 ohm), 600W RMS / 1800W peak, 20mm Xmax, 572 cm2 Sd, neodymium motor
- Build: Langboard Elite MDF, V-groove and dado, 1.5" double baffle with flush outer recess, full divider, 12g OFC side-mounted terminal cup
Financing available. Choose Shop Pay Installments at checkout.
Performance Optimized Down Fire Wide Sealed Dual 12" Shallow Sub Enclosure | Alpine RSW12
More enclosures cut for Alpine subwoofers: Alpine Subwoofer Boxes
Proline X Performance Optimized Down Fire Wide Dual 12" Sealed
41 inch wide, 14 inch deep format. Cut for a pair of Alpine RS-W12 Shallows
The Down Fire Wide Format
Down Fire Wide is the Performance Optimized answer to a space that is long rather than deep or tall. This cabinet runs 41 inches wide by 14 inches deep by 7.75 inches tall: 1 inch shallower front to back than our standard 30 by 15 inch Down Fire platform, and 11 inches longer.
Fourteen inches is the practical minimum for a 12 inch driver: a 12 inch frame needs about 13 inches of baffle. Each RS-W12's 12.82 inch frame sits on the 14 inch deep baffle with about 0.59 inch of baffle outside the flange fore and aft. Because the airspace is spread along 41 inches instead of 30, the wide cabinet usually stands lower than the standard box, and it does here: 7.75 inches against 9.4375 inches for the standard 30 by 15 RS-W12 cabinet.
With the footprint fixed at 41 by 14, height is the free dimension, and it was solved to the airspace: 0.701 cubic feet net per chamber, against 0.70 in the standard box. The motor clears the top panel with 3.75 inches to spare, so clearance did not set the height.
Which one to choose. The standard 30 by 15 is the pick when length is limited. This one is the pick when height or depth is the limit and you have 41 inches of run: under or behind a rear bench, or along a cargo wall. Measure depth and height first; depth is usually the dimension that decides it.
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 mounting depth and the chamber volumes all come from the Alpine RS-W12's own numbers. A Performance box fits your subwoofer. A Performance Optimized box was built for it.
Built Around a Pair of Alpine RS-W12
Two full 12s in a cabinet 7.75 inches tall. Each baffle is bored to the RS-W12's 11-5/8 inch, 295mm cutout, and the internal height is set by a driver Alpine publishes at only 0.05 cubic feet of displacement. A conventional 12 displaces two to four times that.
Cone area is 572 cm² per driver. The RS-W12 ships as the RS-W12D2, dual 2 ohm, or the RS-W12D4, dual 4 ohm, both rated 600 watts RMS and 1800 watts peak with 20mm of one way linear excursion and 54mm of peak to peak mechanical travel. The motor is a high-grade neodymium design driving a 4 inch high-temperature USA-wound voice coil, with Alpine's DD Linear dual magnetic gap, a vented coil former and motor cooling fins. The frame is die-cast aluminum with a black anodized threaded rear mounting frame.
Neodymium is what makes a dual 12 cabinet this size practical. At Alpine's published 0.05 cubic feet displaced each, both drivers together consume less internal volume than a single conventional 12 typically does.
Net Volume, Not Gross
Total gross volume is 1.532 cubic feet, split by the divider into two chambers. After the brace and Alpine's published 0.05 cubic feet of displacement per driver, each chamber holds 0.701 cubic feet net, 1.402 cubic feet net total.
True net, not marketing net. Internal volume is calculated from the machined cavity dimensions and the driver's displacement, not estimated from external dimensions minus wall thickness.
Both coil variants are worth stating because the enclosure ships without drivers. The RS-W12D2 is Qts 0.98 against a 42.04 liter Vas and Fs 28 Hz. The RS-W12D4 is Qts 1.003 against a 43.84 liter Vas and Fs 29 Hz; that Qts is derived from Alpine's published Qes and Qms, since the printed total does not follow from them.
| Coil | System Qtc | Fc | F3 |
|---|---|---|---|
| RS-W12D2, dual 2 ohm | Qtc 1.730 | 49.4 Hz | 33.8 Hz |
| RS-W12D4, dual 4 ohm | Qtc 1.797 | 51.9 Hz | 35.4 Hz |
With a Qts near 1.0 this driver can never reach a flat sealed alignment; every sealed box built for it is underdamped, with a clear rise just above the corner. That lift is what makes a thin neodymium 12 hit hard in a small box. The half-power point still lands in the mid 30s.
These figures are anechoic. Firing down into the floor, the sealed rolloff meets rising cabin gain below about 60 Hz, so in-car response extends below the published F3.
Two Chambers, Not One
This enclosure follows the Proline X standing design rule for dual sealed builds: two fully separate chambers divided by a bonded full-height 3/4 inch MDF panel.
Two drivers sharing one sealed volume interact acoustically. Each driver's compression phase becomes the pressure environment the other is working against, which smears transient response and blurs the alignment each would have on its own. A full divider eliminates that. Each RS-W12 gets its own 0.701 cubic feet net and its own polyfill.
On a long cabinet the divider does structural work as well, tying the front and rear walls together at the centre of the 41 inch span.
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 both chambers airtight under sustained pressure cycling. Corners are square on Down Fire cabinets.
The cabinet measures 41 inches wide by 14 inches deep by 7.75 inches tall, measured in the down fire position, excluding the feet. The 1.75 inch standoffs ship with the enclosure but are not installed, so the installed height is 9.5 inches. Plan the space around that figure.
1.5 Inch Double Baffle
Two 3/4 inch layers laminated to 1.5 inches, the outer layer machined as a flush recess so the driver bolts to the inner layer, with 8/32 threaded inserts at each driver position, stainless machine screws included.
Round Frame, 14 Inch Baffle
The 11.625 inch cutouts sit side by side along the 41 inch length on the 14 inch deep baffle, leaving about 0.59 inch of baffle outside the flange fore and aft. No rotation or special layout is needed for a round frame.
Separate Chambers
A bonded full-height 3/4 inch divider gives each driver its own 0.701 cubic feet and its own light polyfill wall lining, and ties the walls together mid span.
One Shared Terminal Cup
Proline X ABS and carbon fiber composite cup with stainless hardware and copper ring terminals, side mounted and pre-wired in 12 gauge OFC to both driver positions in parallel.
Power and Wiring
Alpine rates each RS-W12 at 600 watts RMS and 1800 watts peak, so the pair takes 1200 watts RMS combined. Target 500 to 600 watts RMS per driver.
One side mounted terminal cup serves both chambers, pre-wired in 12 gauge OFC to both driver positions in parallel. Both versions are dual voice coil, so you set final impedance at the drivers; Alpine's application guide covers every wiring option. Wire both drivers identically so the chambers stay matched.
Bring your own pair of RS-W12D2 or RS-W12D4; the drivers are purchased separately. The enclosure carries a 1 year limited warranty.
Cut for the Driver, Not the Catalog
We cut every Down Fire Wide cabinet to one driver's published cutout, mounting depth and airspace, then build it 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 |
| Compatible Driver | Alpine RS-W12D2 (DVC 2 ohm) or RS-W12D4 (DVC 4 ohm), pair required. Direct fit |
| Enclosure Type | Sealed, dual driver, down fire, floor coupled |
| Intended Fitment | Long, low spaces where height or depth is the limit and 41 in of run is available |
| Firing Direction | Down firing. Feet ship uninstalled, so front or up firing is also possible |
| Chamber Configuration | Two fully separate chambers, full divider, single shared side-mounted terminal cup |
| External Width | 41 in |
| External Depth | 14 in |
| External Height | 7.75 in in the down fire position, excludes standoffs |
| Installed Height | 9.5 in including the 1.75 in standoffs |
| Dimension Reference | All external dimensions measured in down fire position |
| Standard 30 x 15 Version | 9.4375 in tall, 0.70 cu ft net per chamber |
| Internal Volume, Gross | 1.532 cu ft total |
| Per-Chamber Net Volume | 0.701 cu ft after displacement |
| Total Net Volume | 1.402 cu ft |
| Height Set By | Airspace; 3.75 in clearance above the motor |
| Alignment, RS-W12D2, dual 2 ohm (per chamber) | Qtc 1.730, Fc 49.4 Hz, F3 33.8 Hz anechoic |
| Alignment, RS-W12D4, dual 4 ohm (per chamber) | Qtc 1.797, Fc 51.9 Hz, F3 35.4 Hz anechoic |
| Woofer Opening | 11.625 in each |
| Mounting Depth Required | 3.25 in |
| Frame Outer Diameter | 12.82 in |
| Driver Displacement | 0.05 cu ft |
| Driver Fs | 28.00 Hz (Free-Air Resonance) |
| Driver Qts | 0.980 (D2) | 1.003 (D4, derived from Alpine's Qes and Qms) |
| Driver Vas | 42.04 L (D2) | 43.84 L (D4) |
| Cone Area | 572 cm² Each / 1144 cm² Total, Most In The Down Fire Line |
| Driver Xmax (One-Way) | 20mm |
| Driver Xmech (Peak-to-Peak) | 54mm |
| Driver Power Handling | 600 Watts RMS / 1800 Watts Peak Each |
| Driver Voice Coil | 4 Inch, High-Temp USA Wire |
| Driver Motor | High-Grade Neodymium, DD Linear Dual Magnetic Gap |
| Driver Mounting | 8/32 Threaded Inserts | Stainless Steel Machine Screws Included | 2 Sets |
| Voice Coil Configuration | Dual Voice Coil Per Driver, Final Impedance Set At The Drivers |
| Recommended Power Per Driver | 500-600 Watts RMS (Alpine Rated: 600W RMS) |
| Material | Langboard Elite 3/4 in MDF |
| Joinery | V-groove and dado, CNC cut on ShopSabre routers |
| Front Baffle | 1.5 in double baffle, outer layer machined as a flush recess |
| Internal Bracing | Full-height 3/4 in bonded divider plus perimeter cross-brace |
| Corner Profile | Square (Down Fire series standard) |
| Terminal Cup | One Proline X ABS and carbon fiber composite, side mounted, pre-wired 12 gauge OFC to both driver positions |
| Standoffs | 1.75 in, included, shipped uninstalled |
| Damping | Polyfill installed as a light wall lining in each chamber |
| Carpet | Plush black |
| Bundle Options | Enclosure only (bring your own pair of RS-W12D2 or RS-W12D4) |
| Warranty | 1 year limited (enclosure) |
| Built In | 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
0.701 cu ft against a 42.0 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 20.0 mm, and in this alignment a subsonic filter barely moves it.
| Param | Value | Unit | Note |
|---|---|---|---|
| Fs | 28.00 / 29.00 | Hz | free-air resonance |
| Qts | 0.980 / 1.003 | D2 / D4 | |
| Vas | 42.04 / 43.84 | L | equivalent compliance |
| Sd | 572.0 | cm² | effective piston area |
| Xmax | 20 | mm | one-way linear travel |
| Pe | 600 | W | continuous RMS |
| SPL | 80.9 | dB | 1 W / 1 m, derived from T/S |
Driver parameters as published by Alpine R-Series Shallow application guide · Alpine R-Series Shallow application guide (Qts corrected from an impossible printed 1.49). 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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