Proline X
Performance Optimized Down Fire Sealed Dual 12" Enclosure | Alpine RSW12
SKU: PO 12D-S DF RSW
- Alignment: 0.70 cu ft net per chamber, 1.402 cu ft net total. F3 in the low 30 Hz range. Qtc 1.73 / Fc 49 Hz / F3 33.9 Hz (D2), Qtc 1.80 / Fc 52 Hz / F3 35.4 Hz (D4)
- Chambers: Two fully separate sealed chambers, 3/4" MDF full divider, one shared side-mounted terminal cup
- Drivers: Pair of Alpine RS-W12D2 or RS-W12D4, 600W RMS each and 1200W combined, 20mm Xmax, 1144 cm² total cone area, neodymium motor
- Build: Proline X V-groove and dado joinery, double-layer 1.5" front baffles at both positions, perimeter cross-brace, 12g OFC to both driver positions
- Cabinet: 30"W x 15"D x 9.4375"H measured in down fire position, square corners, no standoffs
Financing available. Choose Shop Pay Installments at checkout.
Performance Optimized Down Fire Sealed Dual 12" Enclosure | Alpine RSW12
Proline X Performance Optimized Down Fire Dual 12" Sealed
Cut and tuned for a pair of Alpine RS-W12 Shallows
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, with cabinet height as the variable. A few drivers need a wider or deeper platform. | Compact per driver footprint. 21.5 by 14.5 inches on the 10 inch. |
| Front baffle | Single, 3/4 inch. | Double, 1.5 inch, outer layer machined as a flush recess. | 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 airspace, the cutout and the cabinet height all come from the Alpine RS-W12's own published numbers. A Performance box fits your subwoofer. A Performance Optimized box was built for it.
Built Around the Alpine RS-W12
Two full 12s in a cabinet 9.4375 inches tall on a 30 by 15 inch footprint, shorter than most dual 10 enclosures. Each baffle is bored to the RS-W12's 11-5/8 inch, 295mm cutout, and each driver gets the same alignment the single driver Down Fire cabinet uses. Against one RS-W12 in that alignment, the pair delivers roughly 6 dB more maximum output.
Cone area is 572 cm² per driver and 1144 cm² across the pair, the most in the Proline X Down Fire line. Each RS-W12 ships as the RS-W12D2, dual 2 ohm, or the RS-W12D4, dual 4 ohm, 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 for low distortion at high excursion, a vented coil former, and motor cooling fins. Frames are die-cast aluminum with black anodized threaded rear mounting frames and aluminum dust caps.
Neodymium is what makes a dual 12 cabinet this size practical. A pair of conventional ferrite 12s in separate chambers would demand substantially more height for the same net volume per driver. At Alpine's published 0.05 cubic feet displaced each, both drivers together consume less internal volume than a single conventional 12 typically does. Free air resonance is 28.0 Hz and efficiency bandwidth product runs 24.3 to 24.8 depending on coil, well inside the range that calls for a sealed load.
Net Volume, Not Gross
Total internal gross volume is 1.502 cubic feet, split by the divider into two chambers. After Alpine's published 0.05 cubic feet of displacement per driver, that leaves 0.70 cubic feet net per chamber and 1.402 cubic feet net total. The per chamber number is the one that governs the sound: each driver only ever sees its own 0.70, which sits between Alpine's small and medium sealed recommendations and puts the F3 in the low 30 Hz range.
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.
Both coil variants are worth stating because the enclosure ships without drivers. In 0.70 cubic feet the Dual 2-Ohm, Qts 0.980 against a 42.04 litre Vas, reaches Qtc 1.73 with resonance lifted to 49 Hz and half power at 33.9 Hz. The Dual 4-Ohm, Qts 1.003 against a 43.84 litre Vas, reaches Qtc 1.80 with resonance at 52 Hz and half power at 35.4 Hz. They land close together here, closer than the 10 inch pair does, and both figures are anechoic, before any cabin gain.
Alpine's published sealed range runs 0.6 to 1.5 cubic feet per driver: 0.60 net gives 35 Hz, 0.90 net gives 30.5 Hz, 1.20 net gives 29 Hz. We build 0.70 per chamber because it is what holds a dual 12 under 9.5 inches while still reaching into the low 30s. Firing down into the floor, the sealed rolloff meets rising cabin gain below 60 Hz, and in-car response extends well below the published figure. Wire both drivers identically so both chambers stay matched.
Down Fire Construction
Cut with V-groove and dado joinery on our ShopSabre routers from Langboard Elite 3/4 inch MDF. Every panel joint is a machined interlocking groove that mechanically locks before adhesive is applied, which keeps both chambers airtight under sustained pressure cycling. Perimeter cross-bracing ties the long spans together, which earns its keep on a baffle carrying two 295mm openings. Corners are square on Down Fire cabinets.
Double Baffle, Flush Recess
Both front baffles are 1.5 inches, two bonded 3/4 inch sheets, with the outer layer machined as a flush recess so each driver bolts to the inner layer. That recovers 3/4 inch of internal clearance per chamber. Two sets of 8/32 threaded inserts with stainless machine screws included.
Side-Mounted Terminal Cup
One shared Proline X ABS and carbon fiber composite cup with stainless hardware, pre-wired in 12 gauge OFC to both driver positions. Side mounted so it stays accessible with the baffles facing the floor. Each driver is dual voice coil, so final impedance is set at the drivers.
Separate Chambers
A bonded full height 3/4 inch MDF divider gives each driver its own sealed airspace. Two drivers sharing one volume interact acoustically, each cone's compression phase becoming the other's pressure environment, which smears transients and blurs the alignment. Separate chambers eliminate that. Polyfill is pre-installed in each chamber.
Power and Warranty
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. In a 0.70 cubic foot chamber the cone reaches its 20.0mm one way limit at roughly 1340 to 1341 watts depending on coil, reached first around 48 Hz, far above what the driver can absorb thermally. The voice coil gives up before the suspension does.
A subsonic filter at 25 Hz, 24 dB per octave, stops the cone wasting travel below the passband and moves that same 20.0mm limit out to about 1347 to 1352 watts. That is roughly 1 percent more amplifier for the price of one filter setting.
Both versions are dual voice coil, so you set your final impedance at the drivers, and Alpine's application guide covers every wiring option. The enclosure carries a 1 year limited warranty. Bring your own pair of RS-W12D2 or RS-W12D4; the drivers are purchased separately.
Cut for the Driver, Not the Catalog
Two chambers, each machined to one driver's published numbers rather than one large box split down the middle by eye. Cut on our ShopSabre routers and built one at a time in Tullahoma, Tennessee.
| Series | Proline X Performance Optimized Down Fire |
| Compatible Driver | Alpine RS-W12D2 (DVC 2Ω) or RS-W12D4 (DVC 4Ω) | Pair Required |
| Enclosure Type | Sealed | Dual Driver | Down Fire Geometry | Floor-Coupled |
| Chamber Configuration | Two Fully Separate Chambers | Full Divider | Single Shared Side-Mounted Terminal Cup |
| Firing Direction | Down Firing, Both Drivers Fire Toward Floor |
| External Width | 30 Inches |
| External Depth | 15 Inches |
| External Height | 9.4375 Inches |
| Dimension Reference | All External Dimensions Measured In Down Fire Position |
| Total Internal Gross Volume | 1.502 Cubic Feet |
| Per-Chamber Net Volume | 0.70 Cubic Feet |
| Total Net Volume | 1.402 Cubic Feet |
| Alpine Published Sealed Range | 0.6 - 1.5 Cubic Feet Per Driver |
| Expected F3 | Low 30 Hz Range Per Driver (Between Alpine's 0.60 ft³ / 35 Hz and 0.90 ft³ / 30.5 Hz Points) |
| System Qtc (Per Chamber) | 1.73 (D2) | 1.80 (D4) |
| Predicted Fc (Per Chamber) | 49 Hz (D2) | 52 Hz (D4) |
| Predicted F3 (Per Chamber) | 33.9 Hz (D2) | 35.4 Hz (D4) |
| Driver Fs | 28.00 Hz (Free-Air Resonance) |
| Driver Qts | 0.980 (D2) | 1.003 (D4) |
| 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 Displacement | 0.05 Cubic Feet Each (Published by Alpine) |
| Mounting Depth | Direct Fit |
| Woofer Opening (Each) | 11-5/8 Inches / 295mm (Alpine Spec) |
| Standoffs | Not Used On This Model |
| Material | Langboard Elite 3/4" MDF |
| Construction | ShopSabre CNC / Perimeter Cross-Brace |
| Joinery | V-Groove and Dado (CNC-Cut) |
| Panel Thickness | 3/4 Inch |
| Front Baffle Construction | Double-Layer 1.5" MDF at Both Driver Positions |
| Chamber Divider | 3/4" MDF Full Bonded Panel |
| Corner Profile | Square (Down Fire Series Standard) |
| 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 |
| Terminal Cup | One Proline X ABS/Carbon Fiber Composite | Side Mounted | 12g OFC Pre-Wired to Both Driver Positions |
| Internal Wiring | 12 Gauge OFC, Pre-Wired to Both Driver Positions |
| Damping | Polyfill Pre-Installed Per Chamber |
| Recommended Power Per Driver | 500-600 Watts RMS (Alpine Rated: 600W RMS) |
| Carpet Finish | Plush Black |
| Weight | 44 lb |
| 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
0.70 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 a bigger one once a subsonic filter stops it wasting travel below the passband.
| Param | Value | Unit | Note |
|---|---|---|---|
| Fs | 28.00 | 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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