Proline X
Performance Optimized Down Fire Sealed Dual 12" Enclosure | Alpine RS-W Shallow
SKU: PO 12D-S DF RS
- Alignment: 0.70 cu ft net per chamber - between Alpine's small and medium targets, F3 low 30 Hz range
- 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, 20mm Xmax, 1144 cm² combined cone area
- Cabinet: 30"W x 15"D x 9.4375"H measured in down fire position, square corners
Financing available — choose Shop Pay Installments at checkout.
Performance Optimized Down Fire Sealed Dual 12" Enclosure | Alpine RS-W Shallow
The Performance Optimized Down Fire Sealed Dual 12" Enclosure for the Alpine RS-W Shallow is a two-chamber sealed cabinet built around a pair of Alpine's neodymium shallow 12s. At 9.4375 inches tall on a 30 by 15 inch footprint, it puts two full 12s into a cabinet shorter than most dual 10 enclosures, with roughly 6 dB more maximum output than one RS-W12 in the same alignment.
Each Alpine RS-W12 is available as the RS-W12D2 (dual 2Ω) or RS-W12D4 (dual 4Ω), 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 uses a high-grade neodymium magnet 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. Die-cast aluminum frame, black anodized threaded rear mounting frame, aluminum dust cap, and a trim ring compatible with Alpine's RS grille kit. Cone area is 572 cm² per driver, 1144 cm² across the pair, the most in the Proline X Down Fire line.
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, giving each driver its own dedicated airspace. Two drivers sharing one sealed volume interact acoustically, with each driver's compression phase becoming the other's pressure environment, which smears transient response and blurs the alignment each would have on its own. Separate chambers eliminate that entirely.
Total internal gross volume is 1.502 cubic feet split into two chambers, giving 0.70 cubic feet net per driver after Alpine's published 0.05 cubic foot displacement. That sits between Alpine's small and medium sealed recommendations, placing the F3 in the low 30 Hz range per driver. Each driver sees the same alignment as the single-driver Down Fire cabinet.
Neodymium is what makes this cabinet practical. A pair of conventional ferrite 12s in separate chambers would demand substantially more height for the same net volume per driver. At 0.05 cubic feet displaced each, both of these drivers together consume less internal volume than a single conventional 12 typically does.
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.
Construction is the full Proline X Performance Optimized platform: ShopSabre CNC-cut Langboard Elite MDF with V-groove and dado joinery, perimeter cross-bracing, and double-layer 1.5 inch front baffles (two 3/4 inch sheets bonded) at both driver positions. Corners are square on Down Fire cabinets. Both drivers fire down into the floor, and one side-mounted Proline X ABS/carbon fiber composite terminal cup serves both chambers, fed in parallel to both driver positions with 12 gauge OFC.
Bring your own pair of RS-W12D2 or RS-W12D4 subwoofers. Both are dual voice coil, so you set your final impedance at the drivers. Wire both drivers identically.
Manufactured in Tullahoma, Tennessee. 1-year enclosure warranty.
| Enclosure Type | Sealed | Dual Driver | Down Fire Geometry | Floor-Coupled |
| Chamber Configuration | Two Fully Separate Chambers | Full Divider | Single Shared Side-Mounted Terminal Cup |
| Driver-Specific Fitment | Alpine RS-W12D2 (DVC 2Ω) or RS-W12D4 (DVC 4Ω) | Pair Required |
| Total Internal Gross Volume | 1.502 Cubic Feet |
| Per-Chamber Net Volume | 0.70 Cubic Feet |
| Total Net Volume | 1.402 Cubic Feet |
| Expected F3 | Low 30 Hz Range Per Driver (Between Alpine's 0.60 ft³ / 35 Hz and 0.90 ft³ / 30.5 Hz Points) |
| Alpine Published Sealed Range | 0.6 - 1.5 Cubic Feet Per Driver |
| Driver Power Handling | 600 Watts RMS / 1800 Watts Peak Each |
| Driver Xmax (One-Way) | 20mm |
| Driver Xmech (Peak-to-Peak) | 54mm |
| Cone Area | 572 cm² Each / 1144 cm² Total - Most In The Down Fire Line |
| 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) |
| Cutout Diameter (Each) | 11-5/8 Inches / 295mm (Alpine Spec) |
| Baffle Configuration | Down Firing - Both Drivers Fire Toward Floor |
| Material | Langboard Elite 3/4" MDF |
| Front Baffle Construction | Double-Layer 1.5" MDF at Both Driver Positions |
| Chamber Divider | 3/4" MDF Full Bonded Panel |
| Joinery | V-Groove and Dado (CNC-Cut) |
| Corner Profile | Square (Down Fire Series Standard) |
| Construction | ShopSabre CNC / Perimeter Cross-Brace |
| External Width | 30 Inches |
| External Depth | 15 Inches |
| External Height | 9.4375 Inches |
| Dimension Reference | All External Dimensions Measured In Down Fire Position |
| Voice Coil Configuration | Dual Voice Coil Per Driver - Final Impedance Set At The Drivers |
| Mounting Hardware | 8/32 Threaded Inserts | Stainless Steel Machine Screws Included | 2 Sets |
| Terminal Cup | One Proline X ABS/Carbon Fiber Composite | Side Mounted | 12g 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 | Dark Gray Trunkliner (Standard) or Plush Black (+$10) |
| Bundle Options | Enclosure Only (Bring Your Own Pair of RS-W12D2 or RS-W12D4) |
| 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
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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