Any 6.5 inch subwoofer with a standard cutout whose published parameters suit 0.75 cubic feet vented at 35.0 Hz; check the maker's recommended ported volume against it.

Professional Series 6.5 inch Subwoofer Box

Proline X

Professional Series Ported 6.5" Universal Enclosure

Q: Why is this enclosure tuned to 35.0 Hz?

Tuning is chosen for in-car response rather than an anechoic curve; this cabinet lands at 35.0 Hz on 0.75 cubic feet net.

Q: What makes this Professional rather than Performance Optimized?

The box. A Performance Optimized cabinet is cut to fit a trunk shape on a 1.5 inch double baffle; this one is a full-size front-firing box on a 2.25 inch triple baffle. It carries a 2 year warranty against 1.

Q: Threaded inserts or a kit?

Threaded insert kit included: inserts sized to a standard 6.5 inch subwoofer, the correct drill bit, allen-head screws, allen key and gasket tape.

Q: Is a driver included?

No; this is a universal enclosure.

Q: Would a sealed box be better for me?

That depends on the driver you put in it. A sealed alignment trades output near tuning for a flatter, more controlled response; a vented one like this trades some control for more output. Check the driver's own published sealed and vented recommendations before you choose.

Q: How does the port work?

It is a slot port of 12.0 square inches tuned to 35.0 Hz.

Q: How heavy is it and how does it ship?

18 lb, 23.50" W x 8.25" H x 14.75" D external. It ships as a UPS parcel; the price includes shipping in the 48 states.

SKU: Pro6-P XL

QUICK SPECS

Alignment: 0.75 cu ft net vented at 35.0 Hz
Driver: Universal, not driver-specific
Build: Front-firing standard box, triple 2.25" baffle, dado joinery
Cabinet: 23.50" W x 8.25" H x 14.75" D, 18 lb

Shipping Included No freight charges at checkout on US orders. International orders are quoted live carrier rates at checkout.

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.

$ 262.99

Hurry! Only 5 left in stock.

Financing available. Choose Shop Pay Installments at checkout.

Professional Series Ported 6.5" Universal Enclosure

$ 262.99

Enclosure Type Ported

External Dimensions 23.50" W x 8.25" H x 14.75" D

Gross Volume 1.01 cu ft

Net Volume 0.75 cu ft

Tuning Frequency 35.0 Hz

Port Area 12.0 Square Inches

Weight 18 lbs

INSTALLER'S TAKE

I built this as a universal box because not every six and a half inch driver needs its own pinned enclosure, and a lot of them land in a similar Vas and Fs range.

Before you buy, check your driver's own published ported recommendation against 0.75 cubic feet at 35.0 Hz. If your driver's numbers are close to that, this box will get you close to what its maker specifies; if they are far off, it will not.

Wire whatever coil configuration your driver ships in the way its own manufacturer recommends; that is outside what this box controls.

It ships dry. Do not add polyfill to a ported box. Set your subsonic filter around 28 Hz, below this box's own tuning.

Product Details

Professional Series Ported 6.5" Universal Enclosure

This is a universal enclosure: it is cut to a standard 6.5 inch cutout rather than to one driver, so it fits any subwoofer whose published parameters suit the airspace below.

0.75 cu ft net Universal cutout Built in Tennessee

What this cabinet is

0.75 cubic feet net with a slot port of 12.0 square inches tuned to 35.0 Hz. There is no driver-specific claim on this page: bring the subwoofer you want to run and check its published parameters against the airspace and tuning above before you buy.

This cabinet is cut to a standard cutout rather than one driver, so there is no single alignment to model; the volume and tuning are stated for the buyer to check against their driver's published parameters.

The cabinet

23.50" W x 8.25" H x 14.75" D external. It ships as a UPS parcel; the price includes shipping in the 48 states.

There is no driver pinned to this cabinet and no driver-specific claim is made here: check whatever six and a half inch driver you are installing against its own published ported recommendation before assuming this box is the right size for it. The 0.75 cubic feet and 35.0 Hz tuning are the store's own build figures.

Enclosure Specifications

Series	Proline X Professional
Enclosure Type	Universal \| Front-Firing Standard Box
External Width	23.50 Inches
External Height	8.25 Inches
External Depth	14.75 Inches
Internal Volume (Net)	0.75 Cubic Feet
Port Tuning (Fb)	35.0 Hz
Port Area	12.0 Square Inches
Driver Fitment	Universal, No Driver-Specific Cutout
Material	Langboard Elite 3/4" MDF
Joinery	Dado Joinery (CNC-Cut), Flat Panels
Front Baffle Construction	Triple-Layer 2.25" MDF
Baffle Layers	3
Acrylic	Glossy Black Universal Logo Insert, Outer Layer, Standard
Terminal Cup	Proline X ABS/Carbon Fiber Composite \| Back Panel, Terminal-Cup Side \| 12g OFC Pre-Wired
Damping	None - Ships Dry. Polyfill Detunes A Ported Enclosure
Carpet Finish	Plush Black
Weight	18 lb
Shipping	UPS Ground Parcel, Included In The 48 States
Bundle Options	Enclosure Only
Warranty	2-Year Limited (Enclosure)
Manufactured	Tullahoma, Tennessee, USA

Performance Graphs

Woofer Details

Materials

Material

Built From a Spec Sheet, Not a Sales Sheet

Every Proline X Professional 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, 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.

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 Professional 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.