Proline X
Proline X P8T-S | Triple 8" Sealed Subwoofer Enclosure | V3
SKU: P8T-S III G
- Best For: Triple 8" sealed installs — wide soundstage, shallow depth, high cone area
- Volume: 1.35 ft³ Net (0.45 ft³ per driver)
- Tuning: N/A — Sealed
- Sonic Character: Tight, transient-accurate, wide dispersion
Financing available — choose Shop Pay Installments at checkout.
Proline X P8T-S | Triple 8" Sealed Subwoofer Enclosure | V3
Proline X P8T-S
Triple 8" Sealed Subwoofer Enclosure | V3
Three Drivers. Sealed. Built for Installs Where Depth Is the Limiting Factor.
The Proline X P8T-S is a triple 8" sealed enclosure built for installs that need the cone area of a larger driver without the depth requirement that comes with it. At 1.35 ft³ net — 0.45 ft³ per driver — and sealed alignment, this enclosure delivers controlled, accurate bass across a wide soundstage. Three 8" drivers in sealed alignment produce combined cone area that sits between a single 12" and a single 15" while keeping individual mounting depth at 10.5" — a configuration that opens up install locations that neither of those larger drivers can access.
At 29" wide, 10" tall, and 12" deep, the P8T-S fits across most trunk floors, behind most rear seats in full-size sedans and trucks, and against rear walls in dedicated build vehicles where a 15" would require too much depth. The 10" height and 12" depth profile makes this one of the most versatile multi-driver sealed enclosures in the Performance Series lineup.
A single terminal cup handles wiring for all three drivers internally — all three must be run at the same impedance. Every panel is CNC-cut from Langboard Elite MDF and assembled by hand in our Tennessee facility. Finish options are Dark Gray Trunkliner or Plush Black. Shipping is included.
Why Three 8" Drivers in Sealed Alignment
The triple 8" sealed configuration is an underutilized format in car audio. Most builders default to a single large driver when they want combined output — a 12" or 15" in a ported box. The P8T-S offers a different approach: three smaller drivers in sealed alignment that collectively produce the cone area of a large driver while individually maintaining the low moving mass and transient speed that defines the 8" format.
Each driver bay provides 0.45 ft³ of net internal volume — well within the recommended sealed range for most 8" drivers. All three drivers are working the same correctly-sized air load. The combined output across three drivers is significantly higher than a single 8" sealed, and the sealed alignment preserves the accuracy that makes the 8" format valuable for critical listening and SQ competition builds.
Combined Cone Area
Three 8" drivers produce combined cone area between a single 12" and a single 15" while keeping individual mounting depth at 10.5". A level of output that no single 8" enclosure can approach, from a box that fits where large-format drivers cannot.
Shallow Profile, High Output
At 10" tall and 12" deep, the P8T-S produces large-driver output from a profile that fits behind seats and across trunk floors where a 15" ported box would be completely impractical.
Wide Bass Dispersion
Three drivers spaced across a 29" baffle produce the widest bass dispersion in the Performance Series lineup. Low-frequency output is distributed evenly across the full width of the vehicle cabin.
0.45 ft³ Per Driver — Correctly Sized
Each chamber puts its driver in the center of the recommended sealed range for most 8" subwoofers. No damping material needed. No volume correction required. Three correctly-sized sealed chambers.
Construction: Three Driver Bays, One Build Standard
The P8T-S uses the same Langboard Elite MDF, V-groove and dado joinery, and in-house terminal cup construction as every enclosure in the Proline X Performance Series. Three driver bays require more internal bracing than a single or dual driver build — the P8T-S addresses this with heavy strategic bracing throughout the shared interior that controls panel resonance at the structure level.
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. Three drivers in sealed alignment demand consistent joint integrity across every panel — a single air leak compromises the acoustic seal on the affected chamber. Every seam on the P8T-S is mechanically locked before adhesive is applied.
Single Terminal Cup — All Three Drivers Internal
The P8T-S uses a single ABS/Carbon Fiber Composite recessed terminal cup built in-house at our Tennessee facility. All three 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. All three 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. All three driver cutouts are machined to identical diameter and position. Consistent geometry across every unit.
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 P8T-S spans 29" wide — sized to fit across most full-size trunk floors and behind most rear seats in full-size sedans and trucks. At 10" tall and 12" deep, it clears most behind-seat depth constraints that would eliminate a larger enclosure from consideration.
Dimensional Specifications
External Dimensions: 29" W x 10" H x 12" D
Net Internal Volume: 1.35 ft³ (0.45 ft³ per driver)
Tuning Frequency: N/A — Sealed
Subwoofer Cutout: 7.25"
Max Mounting Depth: 10.5"
Front Panel Thickness: 0.75" Single Baffle
Driver Compatibility
The P8T-S accommodates any 8" subwoofer with a cutout diameter at or below 7.25" and a mounting depth at or below 10.5". All three 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 P8T-S:
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. All three drivers must be run at the same impedance.
Ideal Install Applications
Rear Deck Builds
At 10" tall and 12" deep, the P8T-S is one of the few multi-driver enclosures viable for rear deck installations in sedans where deck depth accommodates the 10.5" max mounting depth.
Behind Rear Seat
The 10" height and 12" depth fit behind most rear seats in full-size sedans and trucks. The 29" width spans most rear floor openings in full-size vehicles without obstructing access to the cargo area.
Shallow Trunk Builds
For vehicles where trunk depth is the limiting factor but width is not — the P8T-S produces large-driver output from a 12" deep footprint that larger ported enclosures cannot match.
High-Excursion Driver Builds
The 10.5" max mounting depth is the deepest specification in the triple 8" format. Competition-grade 8" motors that will not fit shallower enclosures are viable candidates for the P8T-S.
Triple 8" Output. Shallow Profile. Tennessee-Built.
The Proline X P8T-S delivers combined triple 8" output from an enclosure that fits where large-format drivers cannot. Langboard Elite MDF. V-groove and dado joinery. In-house terminal cup. Hand-assembled in Tennessee and inspected before it ships.
Three drivers. Sealed accuracy. Combined cone area between a 12" and a 15" — in a 12" deep box. $199.99 Dark Gray Trunkliner. $209.99 Plush Black. Shipping included.
| Material | Langboard Elite MDF, 3/4" (18mm) |
| Enclosure Type | Sealed |
| Net Internal Volume | 1.35 ft³ (0.45 ft³ per driver) |
| Tuning Frequency | N/A |
| External Dimensions | 29" W x 10" H x 12" D |
| Subwoofer Cutout | 7.25" |
| Max Mounting Depth | 10.5" |
| 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, triple driver internal wiring |
| Wiring | Pre-wired 12g OFC speaker wire |
| Warranty | 1-Year Limited |
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 — 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.
Shop By Series
