Proline - X Dual 6.5" Ported Subwoofer Enclosure - Precision Sound Performance|Proline X|Audio Intensity

Proline X

Proline X P6D-P | Dual 6.5" Ported Subwoofer Enclosure | V3

SKU: P6D-P-G

QUICK SPECS

Best For: Dual 6.5" subwoofer builds / Space-limited installs
Volume: 0.60 ft³ (Net Total)
Tuning: 40Hz
Sonic Character: Tight, High-Output, Dynamic

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.

$ 179.99

Color

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Proline X P6D-P | Dual 6.5" Ported Subwoofer Enclosure | V3

Enclosure Type Ported

External Dimensions 24" x 8" x 12"

Net Volume .6 cu ft

Tuning Frequency 40

Cutout Diameter 5.97"

Front Panel Thickness 1.5"

Max Mounting Depth 7.75"

INSTALLER'S TAKE

I’ve dropped a pair of high-excursion 6.5s into this box for several hatchback builds, and the results consistently catch people off guard. Most guys expect 6.5s to sound like mid-bass drivers, but in this enclosure, they actually dig into the sub-40Hz range without losing that "snap" on the kick drums. The build quality is noticeably better than the "China boxes" you find elsewhere—the 3/4" MDF makes the box feel like a brick, which is exactly what you want to prevent resonance. It’s the easiest way to get real bass without losing your entire trunk.

Product Details

Proline X P6D-P

Dual 6.5" Ported Subwoofer Enclosure | V3

0.60 ft³ Net 40Hz Tuning Ported Bass Reflex 1.5" Double Baffle Langboard Elite MDF Built in Tennessee

Two Drivers. One Ported Enclosure. Built for Compact Installs That Need Real Output.

The Proline X P6D-P is a dual 6.5" slot-ported enclosure built for installs that need the output of two drivers without the footprint of a larger single-driver box. At 0.60 ft³ net and tuned to 40Hz, this enclosure gives two 6.5" drivers the combined air space and port geometry to produce output that a single 6.5" — sealed or ported — cannot replicate. Two drivers in a shared ported alignment produce wider dispersion, more cone area moving air, and a more even bass presentation across the vehicle cabin.

At 24" wide, 8" tall, and 12" deep, the P6D-P fits across the rear floor of most compact vehicles, behind the rear seat of mid-size sedans, and in trunk positions where a single 10" or 12" enclosure would be too deep. It is the correct choice when a single 6.5" is not enough but a larger driver format is not an option.

Every panel is CNC-cut from Langboard Elite MDF to exact internal volume and assembled by hand in our Tennessee facility. The 1.5" double baffle handles the mechanical demands of two drivers sharing a single front panel without flexing. A single terminal cup handles wiring for both drivers internally — both drivers must be run at the same impedance. Shipping is included.

Why Dual 6.5" Ported at 40Hz

Two 6.5" drivers in a ported alignment at 40Hz is not an arbitrary configuration. It is the result of matching driver size, available enclosure volume, and tuning frequency to produce the most output from the smallest possible footprint. Each driver bay is 0.30 ft³ — well within the recommended ported range for most 6.5" subwoofers — and the shared port is tuned to 40Hz, a point that balances deep extension with controlled port velocity on a compact driver.

The 40Hz tuning point on the P6D-P sits slightly higher than the P6-P's 38Hz, which is appropriate for a dual driver configuration — the combined cone area and air mass benefit from a slightly higher tuning point that keeps port velocity in check at the output levels two drivers can achieve. The result is extended, efficient bass that works in compact spaces without the port noise that comes from pushing a small port too hard.

Double the Cone Area

Two 6.5" drivers moving in the same enclosure produce combined cone area that approaches a single 10" driver. The P6D-P generates output that a single 6.5" enclosure — sealed or ported — cannot match regardless of tuning.

Wider Bass Dispersion

Two drivers spaced across a 24" baffle produce a wider, more even bass presentation across the vehicle cabin than a single point source. The low-frequency field is more uniform from driver seat to passenger seat.

40Hz Tuning — Controlled and Extended

40Hz provides strong output through the upper sub-bass range while keeping port velocity manageable for a compact dual-driver enclosure. Deep enough to be felt, controlled enough to stay clean at volume.

Compact Footprint, Serious Output

At 24" wide and 8" tall, the P6D-P delivers dual-driver output from a footprint that fits in spaces a single 10" or 12" ported enclosure would never clear.

Construction: Built to Handle Two Drivers

A dual-driver enclosure places more mechanical demand on the front panel than a single-driver build. Two motors, two cutouts, two mounting flanges — all on the same baffle. The P6D-P addresses this with a 1.5" double baffle and the same Langboard Elite MDF construction that runs across the entire Proline X Performance Series.

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 numbers below are pulled from Langboard's published mill data — not marketing language.

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

1.5" Double Baffle

The front panel on the P6D-P is a 1.5" double baffle — two layers of 3/4" Langboard Elite MDF laminated together. Two drivers mounted side by side on a single baffle create a combined mechanical load that a standard 0.75" panel is not designed to handle long-term. The double baffle eliminates flex, eliminates resonance at the front panel, and holds both driver mounting flanges with the screw retention of a 1.5" solid panel rather than two thin panels trying to act as one.

V-Groove and Dado Joinery

Every panel joint uses V-groove and dado joinery — CNC-cut interlocking grooves that mechanically lock panels before adhesive is applied. The dado creates a tongue-and-groove mechanical interlock that resists shear forces regardless of glue strength. Every corner is locked. Every seam is airtight.

Single Terminal Cup — Shared Internal Wiring

The P6D-P 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. Both drivers must be run at the same impedance — confirm your amplifier output and driver impedances match before wiring. The recessed mount protects terminals from cargo contact. Stainless steel hardware, aluminum landing plates, and copper ring terminals are pre-wired with 12g OFC speaker wire.

ShopSabre CNC Routers

Every panel is machine-cut on ShopSabre industrial CNC routers. Consistent geometry, no hand-cut variance, no gaps at the joints. Both driver cutouts are machined to identical diameter and position.

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 provides a stealth OEM appearance. 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 P6D-P spans 24" wide — sized to fit across most rear floors and behind most rear seats in compact and mid-size vehicles. At 8" tall and 12" deep, it clears most behind-seat depth constraints that would eliminate a larger enclosure from consideration.

Dimensional Specifications

External Dimensions: 24" W x 8" H x 12" D

Net Internal Volume: 0.60 ft³ (0.30 ft³ per driver)

Tuning Frequency: 40Hz

Subwoofer Cutout: 5.97"

Max Mounting Depth: 7.75"

Front Panel Thickness: 1.5" Double Baffle

Driver Compatibility

The P6D-P accommodates any 6.5" subwoofer with a cutout diameter at or below 5.97" and a mounting depth at or below 7.75". Both drivers must be the same model and impedance. Verify published specifications before ordering.

Compatible Driver

The following driver is available from Audio Intensity and has been verified for fitment in the P6D-P:

Triton SX6D4 — 6.5" Dual 4-Ohm Subwoofer →

Note: The Proline X 6" subwoofer will be available shortly and will replace this recommendation once live.

Ideal Install Applications

Behind Rear Seat

At 8" tall and 12" deep, the P6D-P fits behind the rear seat of most compact and mid-size sedans without requiring seat modification. The 24" width spans most rear floor openings cleanly.

Compact Trunk Floor

The low profile makes the P6D-P viable as a flat trunk floor installation in vehicles where available depth is limited but width is not. Measure available trunk depth before ordering.

Rear Deck Builds

The 8" height and dual-driver spread make the P6D-P a strong candidate for rear deck installations in sedans where the deck depth accommodates the 7.75" max mounting depth.

Stealth Daily Installs

Dark Gray Trunkliner and a low-profile form factor make the P6D-P blend into most vehicle interiors. Two drivers produce output that does not match the visual footprint of the enclosure.

Dual Driver Output. Compact Footprint. Tennessee-Built.

The Proline X P6D-P delivers dual 6.5" ported output from an enclosure that fits where larger boxes cannot. Langboard Elite MDF. V-groove and dado joinery. 1.5" double baffle. In-house terminal cup. Hand-assembled in Tennessee and inspected before it ships.

Two drivers. One enclosure. Real bass where it was not possible before. $179.99 Dark Gray Trunkliner. $189.99 Plush Black. Shipping included.

Specifications

Material	Langboard Elite MDF, 3/4" (18mm)
Enclosure Type	Slot-Ported Bass Reflex
Net Internal Volume	0.60 ft³ (Total)
Tuning Frequency	40Hz
External Dimensions	24" W x 8" H x 12" D
Subwoofer Cutout	5.97"
Max Mounting Depth	7.75"
Front Panel Thickness	1.5" (Double Baffle)
Finish	Dark Gray Trunkliner / Plush Black (+$10)
Terminal Cup	ABS/Carbon Fiber Composite, recessed mount, stainless hardware, copper ring terminals
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.