Dual 8 Sub Enclosure|Proline X|Audio Intensity

Proline X Subwoofer Enclosures Proline X Performance P8D-P Ported Enclosure for Dual 8" Subwoofers

Proline X

Proline X P8D-P | Dual 8" Ported Subwoofer Enclosure | V3

SKU: P8D-P III G

QUICK SPECS

Best For: Dual 8" ported installs — maximum output from a compact footprint
Volume: 1.5 ft³ Net (0.75 ft³ per driver)
Tuning: 36Hz
Sonic Character: High output, extended low-frequency, ported efficiency

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.

$ 199.99

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In Stock and Ready to Ship

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Proline X P8D-P | Dual 8" Ported Subwoofer Enclosure | V3

Enclosure Type Ported

External Dimensions 24" x 11" x 16"

Net Volume 1.5cu ft

Tuning Frequency 36Hz

Cutout Diameter 7.25"

Front Panel Thickness .75"

Max Mounting Depth 7.3"

INSTALLER'S TAKE

The 36Hz tuning on this enclosure is the right call for a dual 8" ported build. You get usable output down into the low 30s without the port velocity issues that come with tuning too low on a smaller driver. At 0.75 ft³ per chamber the drivers have enough room to move efficiently without the box working against them — this is not an undersized ported box that chokes output to hit a compact dimension target.
The 7.3" max mounting depth is the spec to check before you order. Standard 8" drivers fit without issue. If you are running a higher-excursion motor with a deep basket, measure your mounting depth first — drivers exceeding 7.3" will not clear the baffle. The two independent terminal cups keep the wiring job clean. Each driver gets its own connection point, impedance loads are handled separately, and you are not dealing with internal splices you did not make.
At 24" wide this fits across most trunk floors and behind most rear seats. If trunk space is tight, measure the available width before ordering — the P8D-P is noticeably wider than the sealed P8D-S.

Product Details

Proline X P8D-P

Dual 8" Ported Subwoofer Enclosure | V3

1.5 ft³ Net 36Hz Tuning Ported Bass Reflex Single Shared Cup Langboard Elite MDF Built in Tennessee

Dual 8" Ported Output. Compact Enough to Fit Where Larger Boxes Cannot.

The Proline X P8D-P is a dual 8" slot-ported enclosure built for installs that need serious output from a footprint that a 10" or 12" ported box cannot match. At 1.5 ft³ net — 0.75 ft³ per driver — and tuned to 36Hz, this enclosure gives two 8" drivers the combined air space and port geometry to produce output that competes with a single 12" ported enclosure while staying within the dimensional constraints of a dual 8" build.

At 24" wide, 11" tall, and 16" deep, the P8D-P is sized for a dedicated trunk build. The 16" depth is the critical dimension — this enclosure fits across most trunk floors but is not a behind-seat option. The 7.3" max mounting depth covers most standard 8" drivers. A single terminal cup handles wiring for both drivers internally — both drivers 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. Port geometry is CNC-cut to exact dimensions — tuning is consistent unit to unit. Finish options are Dark Gray Trunkliner or Plush Black. Shipping is included.

Why Dual 8" Ported at 36Hz

Two 8" drivers in a ported enclosure at 36Hz produce a fundamentally different output profile than either a dual 8" sealed or a single larger ported driver. The combined cone area of two 8" drivers approaches a single 12", and the ported alignment at 36Hz pushes that combined output into the upper sub-bass range where the efficiency peak delivers the most audible impact. The result is output that fills larger vehicles and dedicated listening spaces without requiring a larger driver format.

At 0.75 ft³ per driver, each chamber is well within the recommended ported range for most 8" subwoofers. Port velocity stays controlled at these volumes — no chuffing, no audible port noise at real-world listening levels. Both drivers are working the same correctly-sized air load at the same tuning frequency.

Combined Cone Area

Two 8" drivers in ported alignment produce combined cone area and output that approaches a single 12" ported enclosure — in a box that is significantly shorter and fits installations a 12" cannot.

36Hz Tuning — Efficient and Extended

36Hz places the port output peak in the upper sub-bass range where bass impact is most audible. Strong output from the mid-30s through the upper bass range without the port velocity issues that come with tuning too low on a dual 8" build.

0.75 ft³ Per Driver

Each driver bay provides 0.75 ft³ of net internal volume — the center of the recommended ported range for most 8" drivers. Both drivers operate at the same correctly-sized air load with controlled port velocity at listening levels.

Wide Bass Dispersion

Two drivers spaced across a 24" baffle produce a wider, more even bass presentation across the vehicle cabin than a single driver of any size. Low-frequency output is distributed more evenly from driver seat to passenger seat.

Construction: CNC-Cut Port Geometry, Single Shared Terminal Cup

The P8D-P uses the same Langboard Elite MDF and V-groove and dado joinery construction as every enclosure in the Proline X Performance Series. The port geometry is CNC-cut to exact dimensions — port length and cross-section are consistent unit to unit, which means tuning frequency does not vary between enclosures. A single terminal cup handles both drivers internally.

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

Every panel joint uses V-groove and dado joinery — CNC-cut interlocking grooves that mechanically lock panels before adhesive is applied. Port panels are joined with the same interlocking geometry as the enclosure walls — consistent, airtight, and resistant to shear forces at the joint level rather than relying solely on adhesive.

Single Terminal Cup — Same Impedance Required

The P8D-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 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.

CNC-Cut Port Geometry

Port length, cross-section, and position are machine-cut to exact dimensions on ShopSabre CNC routers. Tuning frequency is consistent unit to unit — no hand-cut variance in port dimensions.

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 P8D-P is a dedicated trunk build. At 24"W x 11"H x 16"D, the 16" depth makes this a trunk floor enclosure — not a behind-seat option. Measure your available trunk depth carefully before ordering.

Dimensional Specifications

External Dimensions: 24" W x 11" H x 16" D

Net Internal Volume: 1.5 ft³ (0.75 ft³ per driver)

Tuning Frequency: 36Hz

Subwoofer Cutout: 7.25"

Max Mounting Depth: 7.3"

Front Panel Thickness: 0.75" Single Baffle

Driver Compatibility

The P8D-P accommodates any 8" subwoofer with a cutout diameter at or below 7.25" and a mounting depth at or below 7.3". 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 P8D-P:

Image Dynamics ID8 V4 → Prodigy NB2-8D4 → Image Dynamics IDQ8 V4 → Prodigy NB5-8D4 → Arc Audio Arc Series 8" →

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

Dedicated Trunk Builds

At 24" wide and 16" deep, the P8D-P is designed to span a trunk floor. The 16" depth requires a dedicated trunk install — measure your available depth before ordering.

High-Output Compact Systems

Two 8" drivers in ported alignment produce output that competes with a single 12" ported enclosure in a box that fits installations a 12" cannot reach. Maximum output from the dual 8" format.

Wide Soundstage Builds

Two drivers spaced across a 24" baffle produce a wider bass presentation than any single-driver enclosure. For installs where even bass distribution across the full cabin width is the goal.

Step Up From Sealed

For builds currently running the P8D-S that need more output and lower frequency extension — the P8D-P is the direct step up. Same driver compatibility, significantly more output.

Dual 8" Ported Output. Tennessee-Built. Shipping Included.

The Proline X P8D-P delivers dual 8" ported performance from an enclosure that fits where larger boxes cannot. Langboard Elite MDF. V-groove and dado joinery. CNC-cut port geometry. In-house terminal cup. Hand-assembled in Tennessee and inspected before it ships.

Two drivers. Ported efficiency. Output that competes with a single 12". $199.99 Dark Gray Trunkliner. $209.99 Plush Black. Shipping included.

Specifications

Material	Langboard Elite MDF, 3/4" (18mm)
Enclosure Type	Slot-Ported Bass Reflex
Net Internal Volume	1.5 ft³ (0.75 ft³ per driver)
Tuning Frequency	36Hz
External Dimensions	24" W x 11" H x 16" D
Subwoofer Cutout	7.25"
Max Mounting Depth	7.3"
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.