Proline X Performance P12D - S Dual 12 - inch Sealed Subwoofer Box|Proline X|Audio Intensity

Proline X

Proline X P12D-S | Dual 12" Sealed Subwoofer Enclosure | V3

SKU: P12D-S III-G

QUICK SPECS

Best For: Dual 12" sealed installs — accurate bass, wide soundstage
Volume: 2.0 ft³ Net — shared air space, heavily braced
Tuning: N/A — Sealed
Sonic Character: Tight, transient-accurate, flat response

Shipping Included No freight charges at checkout. What you see is what you pay.

Built in Tennessee CNC cut from 3/4" Langboard Elite MDF. V-groove and dado joinery.

Advanced Terminal Cup Built in-house. ABS/Carbon Fiber. Stainless steel hardware. Copper ring terminals.

$ 219.99

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Proline X P12D-S | Dual 12" Sealed Subwoofer Enclosure | V3

Enclosure Type Sealed

External Dimensions 28" x 14.5" x 12.5"

Net Volume 2.0ftcu ft

Tuning Frequency N/A

Cutout Diameter 11.13"

Front Panel Thickness .75"

Max Mounting Depth 10"

INSTALLER'S TAKE

The 2.0 ft³ shared air space on this enclosure gives dual 12" drivers a well-proportioned sealed load. The shared chamber with heavy internal bracing keeps the build compact while distributing the air load evenly across both drivers — both are working the same air mass, which produces a more cohesive low-frequency response than two undersized independent chambers would.
The 7" max mounting depth covers most standard 12" drivers. High-excursion competition motors with extended baskets are the exception — check your driver's published mounting depth before ordering. At 28" wide and 12.5" deep this enclosure fits across most trunk floors and behind most rear seats in full-size trucks and sedans. Single terminal cup handles both drivers internally — both must be run at the same impedance. Confirm your amplifier output and driver impedances before wiring.

Product Details

Proline X P12D-S

Dual 12" Sealed Subwoofer Enclosure | V3

2.0 ft³ Net Sealed Alignment Shared Air Space 7" Max Depth Langboard Elite MDF Built in Tennessee

Two 12" Drivers. One Sealed Enclosure. Wide Soundstage, Controlled Bass.

The Proline X P12D-S is a dual 12" sealed enclosure built for installs that need the output and soundstage width of two drivers without the depth requirement of a large single-driver ported box. At 2.0 ft³ net in a shared air space with heavy internal bracing, and sealed alignment, this enclosure delivers controlled, accurate bass across a presentation that no single 12" can replicate. Two 12" drivers in sealed alignment produce combined cone area that approaches a single 18" driver while maintaining the transient accuracy and flat response that sealed alignment delivers.

At 28" wide, 14.5" tall, and 12.5" deep, the P12D-S fits across most full-size trunk floors without the depth commitment of a single 12" ported box or a dual 12" ported build. The 7" max mounting depth covers the majority of standard 12" drivers. Both drivers share a single terminal cup — both must be run at the same impedance.

Every panel is CNC-cut from Langboard Elite MDF to exact internal volume and assembled by hand in our Tennessee facility. Finish options are Dark Gray Trunkliner or Plush Black. Shipping is included.

Why Dual 12" Sealed

Two 12" drivers in sealed alignment is one of the most capable bass configurations available in a compact depth profile. The combined cone area approaches a single 18" driver — but at 12.5" deep, the P12D-S fits across a full-size trunk floor where an 18" ported box would require an entirely custom build to accommodate. The sealed alignment preserves the transient accuracy and flat response that makes the 12" format valuable for musical listening, applied at a combined output level that fills large vehicles and pressurizes the cabin at moderate power levels.

The shared 2.0 ft³ air space with heavy internal bracing provides both drivers with a larger effective acoustic load than two individual 1.0 ft³ separated chambers — the drivers interact with a combined air mass that produces a more cohesive low-frequency response across the full 28" baffle width.

Combined Cone Area

Two 12" drivers produce combined cone area approaching a single 18" while maintaining the transient accuracy and flat response of sealed alignment. More output than any single 12" at any power level — in a 12.5" deep enclosure.

Compact Depth Profile

At 12.5" deep, the P12D-S fits across full-size trunk floors where a single 12" ported or dual 12" ported build would require significantly more depth. The output-to-depth ratio is the strongest argument for this configuration.

Wide Bass Presentation

Two drivers spaced across a 28" baffle produce a wider, more even low-frequency field than any single point source. Bass is distributed more evenly across the full cabin width from driver seat to passenger seat.

Shared Air Space — Cohesive Response

The shared 2.0 ft³ interior with heavy internal bracing provides a larger effective acoustic load per driver than separated chambers. Both drivers work the same combined air mass for a more cohesive low-frequency response across the full 28" baffle.

Construction: Shared Air Space, Maximum Bracing, Single Terminal Cup

The P12D-S uses the same Langboard Elite MDF and V-groove and dado joinery construction as every enclosure in the Proline X Performance Series. The interior is a single shared air space with heavy strategic bracing throughout — not two separated chambers. Two 12" motors in a shared air space generate significant combined pressure on every panel simultaneously. The bracing strategy on the P12D-S is calculated to control panel resonance at the output levels two 12" drivers can produce.

Langboard Elite MDF — Named, Verified, Documented

Every panel is cut from Langboard Elite MDF — 3/4" (18mm), a named, mill-documented panel stock produced in the United States. The specifications below are pulled directly from Langboard's published mill data.

Langboard Elite — Published Mill Data

Density: 48.5 lbs/ft³ — higher density means less porosity, better screw retention, and reduced resonance

Internal Bond: 200 psi — resistance to delamination under sustained bass pressure cycling

Modulus of Elasticity: 410,000 psi — panel stiffness under load; less flex means less resonance

Face Screw Holding: 325 lbs — baffle hardware stays locked under vibration

Edge Screw Holding: 250 lbs — joint integrity at every panel edge connection

V-Groove and Dado Joinery

Pre Assembly showing dados and vcuts

Every panel joint uses V-groove and dado joinery — CNC-cut interlocking grooves that mechanically lock panels before adhesive is applied. On an enclosure spanning 28" wide with two 12" motors generating combined pressure on every panel simultaneously, joint integrity and panel rigidity are not optional — they are the structural foundation the enclosure depends on to maintain acoustic performance over time.

Single Terminal Cup — Same Impedance Required

The P12D-S uses a single ABS/Carbon Fiber Composite recessed terminal cup built in-house at our Tennessee facility. Both drivers are wired internally to the cup with stainless steel hardware, aluminum landing plates, and copper ring terminals, pre-wired with 12g OFC speaker wire. Both drivers must be run at the same impedance — confirm your amplifier output and driver impedances match before wiring.

ShopSabre CNC Routers

Every panel is machine-cut on ShopSabre industrial CNC routers. Both driver cutouts are machined to identical diameter and position across the 28" baffle. Consistent geometry across every unit produced.

Hand-Assembled in Tennessee

Every enclosure is hand-assembled at our Tennessee facility and inspected before it ships. No overseas manufacturing. No batch assembly shortcuts.

Dark Gray Trunkliner or Plush Black

Both finish options are professionally applied. Dark Gray Trunkliner blends with factory trunk materials. Plush Black delivers the traditional aftermarket look. Both are durably bonded for long-term wear.

Shipping Included

No freight charges at checkout. The price you see is the price you pay. The enclosure ships assembled and ready to install.

Fitment Guide

The P12D-S spans 28" wide and sits at only 12.5" deep — a compact depth profile for a dual 12" enclosure. It fits across most full-size trunk floors without the depth commitment of any ported 12" build.

Dimensional Specifications

External Dimensions: 28" W x 14.5" H x 12.5" D

Net Internal Volume: 2.0 ft³ — shared air space, heavily braced

Tuning Frequency: N/A — Sealed

Subwoofer Cutout: 11.15"

Max Mounting Depth: 7"

Front Panel Thickness: 0.75" Single Baffle

Driver Compatibility

The P12D-S accommodates any 12" subwoofer with a cutout diameter at or below 11.15" and a mounting depth at or below 7". Both drivers must be the same model and impedance. Verify published specifications before ordering.

Compatible Drivers

The following drivers are available from Audio Intensity and are compatible with the P12D-S:

Prodigy NB2-12D4 → Image Dynamics ID12 V4 → Prodigy NB3-12D4 → Arc Audio ARC12 D2 →

Always verify cutout diameter and mounting depth against your specific driver's published specifications before ordering. Both drivers must be run at the same impedance.

Ideal Install Applications

Full Trunk Floor Build

At 28" wide and 12.5" deep, the P12D-S spans a full-size trunk floor with less depth than most single 12" ported enclosures. A dual 12" sealed build that fits where ported builds of any size cannot.

SQ and DSP-Controlled Systems

Two sealed 12" drivers produce the combined output and wide bass presentation that SQ competition builds demand — with the flat sealed response that DSP-controlled systems can tune precisely. The most capable sealed configuration in the Performance Series lineup.

High-Output Daily Systems

Combined cone area approaching a single 18" in sealed alignment produces output that fills large vehicles and pressurizes the cabin at moderate power levels. A strong platform for daily high-output builds that prioritize accuracy over raw SPL.

Step Up From Single 12" Sealed

For builds running the P12-S that need more output and wider bass presentation without switching to a ported alignment — the P12D-S is the direct step up. Same driver compatibility, significantly more output and soundstage width.

Dual 12" Accuracy. Compact Depth. Tennessee-Built.

The Proline X P12D-S delivers dual 12" sealed performance in a 12.5" deep enclosure that fits where larger builds cannot. Langboard Elite MDF. V-groove and dado joinery. Heavy internal bracing. In-house terminal cup. Hand-assembled in Tennessee and inspected before it ships.

Two drivers. Sealed accuracy. Combined cone area approaching a single 18" — in a compact trunk floor footprint. $219.99 Dark Gray Trunkliner. $229.99 Plush Black. Shipping included.

Specifications

Material	Langboard Elite MDF, 3/4" (18mm)
Enclosure Type	Sealed
Net Internal Volume	2.0 ft³ Net — shared air space, heavily braced
Tuning Frequency	N/A
External Dimensions	28" W x 14.5" H x 12.5" D
Subwoofer Cutout	11.15"
Max Mounting Depth	7"
Front Panel Thickness	0.75" Single Baffle
Finish	Dark Gray Trunkliner / Plush Black (+$10)
Terminal Cup	ABS/Carbon Fiber Composite, recessed mount, stainless hardware, copper ring terminals — single cup, dual driver internal wiring
Wiring	Pre-wired 12g OFC speaker wire
Warranty	1-Year Limited

Materials

Material

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.

Specifications

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

Internal Bond

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.

Stiffness

410,000 psi MOE — Less Flex, Less Resonance

The modulus of elasticity measures panel stiffness — 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.

Screw Holding

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.

Sourcing

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.