Proline X Pro 8-P X8 Professional Series ported enclosure, front baffle with slot port and branded gloss black acrylic insert, 28 by 14 inches, 34.4 square inches of port area.
Proline X Pro 8-P X8 Professional Series ported enclosure, front baffle with slot port and branded gloss black acrylic insert, 28 by 14 inches, 34.4 square inches of port area.

Proline X

Professional Series Ported 8" Enclosure | Sundown Audio X-Series v.3 8" X-8

SKU: Pro 8-P X8

QUICK SPECS
  • Alignment: 1.49 cu ft net vented at 32.5 Hz. F3 28.0 Hz anechoic, 4.42 dB passband ripple
  • Driver: Sundown Audio X-Series v.3 8" X-8 D2, 800 W RMS, 19.0 mm Xmax, 48.50 Hz Fs
  • Build: Front-firing standard box, 2.25" three-layer baffle with the woofer flush-mounted in the outer layer, Sundown Audio logo acrylic, dado joinery, 34.4 sq in front slot port beside the woofer wrapped with two bends, along the back and forward along the far side, port and excursion gated at 800 W
  • Cabinet: 28.00" W x 14.00" H x 17.50" D, 56 lb, threaded insert kit included
Shipping Icon
Shipping Included No freight charges at checkout on US orders. International orders are quoted live carrier rates at checkout.
USA Flag Rounded
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.
$ 471.99
In Stock and Ready to Ship
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Proline X Pro 8-P X8 Professional Series ported enclosure, front baffle with slot port and branded gloss black acrylic insert, 28 by 14 inches, 34.4 square inches of port area.

Professional Series Ported 8" Enclosure | Sundown Audio X-Series v.3 8" X-8

Regular price $ 471.99
Sale price $ 471.99 Regular price
Unit price

More enclosures cut for Sundown Audio subwoofers: Sundown Audio Subwoofer Boxes

Enclosure Type Ported
External Dimensions 28.00" W x 14.00" H x 17.50" D
Gross Volume 2.67 cu ft
Net Volume 1.49 cu ft
Tuning Frequency 32.5 Hz
Port Area 34.4 Square Inches
Shipping Weight 62 lbs
INSTALLER'S TAKE

I built this box on Sundown's own published numbers for the X-8, and the D2 and D4 versions of this driver share the same basket, so one cabinet and one listing covers both.

The port here is modeled clean past the coil's own 800 watt rating, out to 1411 watts, before mouth velocity becomes the limiting factor rather than the coil.

Wire the D2 coil in series for 4 ohms or parallel for 1 ohm; wire the D4 coil in series for 8 ohms or parallel for 2 ohms. A parallel load under 1 ohm needs an amplifier rated for it.

Sundown Audio publishes no mounting hole locations for the X-Series v.3 8" X-8, so the inserts are not in the baffle when the box arrives. The insert kit is in the box: set the inserts where the woofer's own holes fall, with the drill bit and the 2.5 inch allen-head screws in the kit, and lay the gasket tape before the woofer goes down.

The Performance Optimized wedge is the smaller and cheaper box, and I try it first for every driver. I could not make its port keep up with the X-Series v.3 8" X-8: the calmest port that fits that envelope goes noisy at about 524 watts, under what this coil is rated to take, so I did not sell you that box.

It ships dry. Do not add polyfill to a ported box. Set your subsonic filter at 28 Hz.

Product Details
Enclosure Specifications
Performance Graphs
Woofer Details
Materials
Product Details

Proline X Professional 8" Ported

A ported eight-inch box built to Sundown's own numbers for the X-Series v.3 X-8

1.49 cu ft net Tuned 32.5 Hz F3 28.0 Hz 2.25" three-layer baffle Cut for the X-Series v.3 8" X-8 Built in Tennessee
1.49cu ft net
32.5Hz tuning
28.0Hz F3 anechoic
34.4sq in port area

Why this driver is vented at 32.5 Hz

The Sundown Audio X-Series v.3 11 inch X-8 D2 carries an 8.7 inch frame and a full 7.0 inch mounting depth, and this cabinet gives it 1.495 cubic feet net, vented at 32.5 Hz through a 34.4 square inch port beside the woofer on the front face. F3 lands at 28.0 Hz with 4.42 dB of passband ripple. The 28.0 by 14.0 by 17.5 inch enclosure carries a two-bend wrap port, and the D4 version of this driver shares the same cabinet.

Threaded insert kit ships with this box. Sundown Audio does not publish the mounting hole locations for the X-Series v.3 8" X-8, so we cannot install the threaded inserts before it ships. The threaded insert kit comes in the box instead: inserts sized to the woofer, the correct drill bit, 2.5 inch allen-head screws, an allen key and woofer gasket tape. You set the inserts when you mount the woofer, and this box ships with one kit.

Sundown publishes a Qts of 0.486 for the X-8 D2, and the figure checks out against their own Qes of 0.533 and Qms of 5.542. The gate here is measured at the coil's rated power, 800 W, and the port stays clean past that rating, modeled to 1411 W before mouth velocity becomes the limiting factor. Ripple across the passband holds at 4.42 dB across the full 17.5 inch depth this cabinet gives the motor.

What makes it Professional

Three-layer baffle, flush mount

Three layers of 3/4 inch Langboard Elite make a 2.25 inch front. The outer layer is routed to the flange, so the woofer sits flush with the face; the two layers behind it carry the mounting hardware and the load.

Sundown Audio logo acrylic

A glossy black acrylic insert with the Sundown Audio mark sits in the outer layer beside the woofer. It is standard on every Professional cabinet.

Threaded insert kit ships with this box

Threaded insert kit included, inserts NOT pre-installed: the manufacturer publishes no mounting hole locations, so the kit ships with the box for installation when the woofer goes in: 8 to 12 inserts sized to the woofer, the correct drill bit, 2.5 inch allen-head screws, allen key and gasket tape.

Port gated at 800 W

The 34.4 square inch slot beside the woofer is sized so the channel runs 15.1 metres per second and the mouth 10.3 metres per second at the driver's rated power, under the 17 metres per second where a slot starts to chuff. The channel runs 11.00 inches along its wall, turns across the back wall for 19.25 inches, then turns again and runs forward along the far side for 2.91 inches: a two-bend wrap, which is how a 32.5 Hz tuning fits a 17.50 inch deep box.

Why this is a Professional build

Every driver is run through the Performance Optimized wedge and down-fire before this chassis; the Professional box is where a driver lands when that smaller envelope, 30 inches wide and 18 inches deep with a triangular side port, cannot give it what it needs at its rated power. The X-Series v.3 8" X-8 did not clear the port gate there. The calmest wedge port that fits that envelope is 13.0 square inches at 30.0 by 10.88 by 15.15 inches, and its mouth runs 21.0 metres per second at 800 W against the 17 metres per second line where a port starts to chuff. That port would stay clean to about 524 W. The slot on this box reaches 34.4 square inches and holds the mouth at 10.3 metres per second at 800 W.

What the price covers

Every Professional cabinet is priced the same way, by its size: this one is 3.97 cubic feet outside. Delivery to the 48 states is inside the price; it ships as a 56 lb parcel and checkout adds nothing.

What Sundown Audio recommend

Sundown Audio publish a vented box for the X-Series v.3 8" X-8 at 0.75 cubic feet on a basis they do not state, tuned to 32.0 Hz. This cabinet holds 1.49 cubic feet net and tunes to 32.5 Hz. They call for a port area of 12-16 sq in. The extra air lowers the low corner rather than raising output at tuning.

The cabinet

28.00" W x 14.00" H x 17.50" D external. Two windowed braces run front to back either side of the woofer, clearing the cutout by two and a half inches. The box ships dry: polyfill detunes a ported alignment. This is our single-eight ported envelope built around the X-8's own frame and motor depth. It ships as a parcel.

Nothing about this X-8 D2 build needed an estimate: frame, cutout, and mounting depth are Sundown's own published dimensions, and the Qts figure agrees with what its own Qes and Qms predict. The D4 coil shares the same basket and fits this same cabinet without a dimensional change. Sundown Audio does not publish the mounting hole locations for the X-Series v.3 8" X-8, so we cannot install the threaded inserts before it ships. The threaded insert kit comes in the box instead: inserts sized to the woofer, the correct drill bit, 2.5 inch allen-head screws, an allen key and woofer gasket tape. You set the inserts when you mount the woofer, and this box ships with one kit.

The numbers to respect

Set a 26 Hz subsonic filter, 24 dB per octave. Below tuning the vent stops loading the cone; with the filter in place the cone reaches 11.0 mm of its 19.0 mm at 800 W.

Enclosure Specifications
SeriesProline X Professional
Driver-Specific FitmentSundown Audio X-Series v.3 8" X-8 D2 (D2)
Enclosure TypePorted | Front-Firing Standard Box
External Width28.00 Inches
External Height14.00 Inches
External Depth17.50 Inches
Internal Volume (Gross)2.67 Cubic Feet
Internal Volume (Net After Displacement)1.49 Cubic Feet
Port TypeVertical Slot Beside The Woofer | Front Exit | Two 90 Degree Bends, Wrapped Along The Back And Far Side
Port Geometry2.75 x 12.50 Inches, 34.4 Square Inches, 43.16 Inches Of Path
Port Area34.4 Square Inches
Port Tuning (Fb)32.5 Hz
Port Mouth1/2 In Roundover On All Four Edges, 50.6 Square Inches At The Face
Port Air Velocity15.1 m/s In The Channel, 10.3 m/s At The Mouth, At 800 W (17.0 m/s Chuff Threshold)
Design Power Basis800 W RMS (1.2 x The Driver Rating) For Port Velocity And Excursion
Predicted F328.0 Hz (Anechoic)
Passband Ripple4.42 dB (Anechoic)
Subsonic Filter26 Hz High-Pass, 24 dB/Octave - REQUIRED On A Vented Enclosure
Driver Fs48.50 Hz
Driver Qts0.486
Driver Qes / Qms0.533 / 5.542
Driver Vas3.933 Liters / 0.139 Cubic Feet
Driver Sd198.9 Square Centimeters
Driver Mms157.13 g
Driver BL23.22
Driver Re6.0 Ohm
Driver Xmax19mm (One-Way)
Driver Displacement0.13 Cubic Feet (Published by Sundown Audio)
Driver Sensitivity81.1 dB
Driver Power Handling800 Watts RMS
Driver Overall Diameter8.700 Inches (Sundown Audio Spec)
Mounting Depth Required7.000 Inches (Sundown Audio Spec)
Cutout Diameter7.375 Inches (Sundown Audio Spec)
Flush Mount Recess9.625 Inches In The Outer Layer
MaterialLangboard Elite 3/4" MDF
ConstructionShopSabre CNC / Two Windowed Braces Front To Back Either Side Of The Woofer
JoineryDado Joinery (CNC-Cut), Flat Panels
Front Baffle ConstructionThree 3/4" MDF layers, 2.25" total | Woofer Flush-Mounted In The Outer Layer
Baffle Layers3
AcrylicGlossy Black Sundown Audio Logo Insert, Outer Layer, Standard
Mounting HardwareThreaded Insert Kit Included: 8-12 Inserts, Drill Bit, 2.5 In Allen-Head Screws, Allen Key, Gasket Tape
Voice Coil ConfigurationD2
Terminal CupProline X ABS/Carbon Fiber Composite | Back Panel, Terminal-Cup Side | 12g OFC Pre-Wired
DampingNone - Ships Dry. Polyfill Detunes A Ported Enclosure
Recommended Power560-800 Watts RMS (Sundown Audio Rated: 800W RMS)
Carpet FinishPlush Black
Shipping Weight62 lb
ShippingUPS Ground Parcel, Included In The 48 States
Bundle OptionsEnclosure Only (Bring Your Own Sundown Audio X-Series v.3 8" X-8)
Warranty2-Year Limited (Enclosure)
ManufacturedTullahoma, Tennessee, USA
Performance Graphs
Net airspace
1.49
cu ft
Tuning
32.5
Hz · Fb
Half power
28.0
Hz · F3, anechoic
Xmax at
2375
W RMS · 26 Hz subsonic
With NO filter
1092
W RMS · unfiltered
Port
10.3
m/s at the mouth · 800 W

01Is this driver right for a ported box?

Efficiency bandwidth product places the motor before anything else is decided.

EBP = Fs ÷ Qes = 91.0
SEALED 0–50 TRANSITION 50–100 PORTED 100–150 0 50 100 150 EBP 91.0
Sundown Audio X-Series v.3 8" X-8 D2 · EBP 91.0
Between 50 and 100 a driver takes either load, and the choice becomes one of priorities rather than of physics. The Sundown Audio X-Series v.3 8" X-8 D2 reads 91.0. Ported buys output and low-end reach around tuning; sealed buys a shallower rolloff below it. This cabinet takes the first trade.

02What the box does to it

1.49 cu ft net against a 3.9 L Vas, vented at 32.5 Hz.

Fb = 32.5 Hz  ·  F3 = 28.0 Hz  ·  passband ripple 4.42 dB
20 30 50 70 100 150 200 +8 +4 0 −4 −8 −12 −16 −20 −24 −28 −32 FREQUENCY · Hz LEVEL · dB −3 dB Fb 32.5
Sundown Audio X-Series v.3 8" X-8 D2 · Fb 32.5 Hz, F3 28.0 Hz
Anechoic, before any cabin gain, with the 26 Hz subsonic filter already applied. The vent takes over below 32 Hz and the cone stops doing the work there, which is what holds travel down at the bottom of the passband.

03Ported vs Sealed

No sealed comparison is shown for this driver.

A ported-versus-sealed chart is only worth reading against a sealed box someone would actually build: the one we make for the driver, or the one its maker recommends. Neither exists for the Sundown Audio X-Series v.3 8" X-8 D2 — we do not build a sealed enclosure for it and Sundown mark it Not Recommended for a sealed enclosure — so rather than compare this cabinet against itself stuffed and sealed, a box no one would build, the comparison is left out.

04The watts that reach Xmax (in this enclosure)

Travel scales with the square root of power, so there is one wattage that puts the cone exactly on Sundown's published 19.0 mm. The two traces are the same cabinet with the subsonic filter switched on and switched off.

PXmax = 2375 W with a 26 Hz subsonic  ·  1092 W with none  →  the filter is worth 2.2×
20 30 50 70 100 150 200 0 4 8 12 16 20 24 FREQUENCY · Hz CONE TRAVEL · mm PAST LINEAR TRAVEL · Xmax 19.0 mm 2375 W reaches Xmax here
2375 W · subsonic at 26 Hz, 24 dB/oct1092 W · no subsonic filterXmax 19.0 mm one-way, published
Each trace touches the limit and no further, because each is drawn at the exact power that puts the cone on 19.0 mm. With a 26 Hz subsonic that takes 2375 W, reached first at 28 Hz. Take the filter away and the same cabinet reaches 19.0 mm on 1092 W — the filter is worth 2.2× the safe power. A vent unloads the cone below tuning, so there is nothing holding it once the box stops loading: on a sealed build a subsonic filter is an improvement, here it is required equipment. The unfiltered trace is still rising where this chart stops at 20 Hz, so treat 1092 W as a bound rather than a floor. Every wattage on this page is a MECHANICAL limit, not an electrical one. It is the power at which the cone runs out of linear travel in this cabinet, and nothing more. What the voice coil can dissipate as heat is a separate ceiling set by the driver, not by the box — Sundown rate this one at 800 W RMS, and that is the number that binds first here: heat stops you before travel does, so treat 800 W as the ceiling and the travel figures above as headroom. Final wired impedance, amplifier output and how long you hold the level are all electrical questions this graph does not answer.
Woofer Details
Sundown treats the X 8 v.3 as the most they can get out of their 8 inch frame, and credits the gain over the earlier versions to the spider and surround rather than the motor. Their page publishes two mounting depths, 6.8 inches in one table and 7.0 in the other; this cabinet is cut to the deeper figure so it clears either. This enclosure is cut for 7.00 in of mounting depth and a 7.375 in cutout, taken from Sundown Audio's published figures rather than measured off a sample.
DriverSundown Audio X-Series v.3 8" X-8
Coil OptionsDual 2 Ohm or Dual 4 Ohm
BasketCustom Tooled 8 Inch Platform
MotorAluminum Magnet ID Shorting Ring
Motor Diameter6.88 in
Power, RMS800 W
Peak Power1600 W
Sensitivity81.1 dB (D2), 80.8 dB (D4), SPL (1W/1m)
Mounting Depth7.00 in
Cutout Diameter7.375 in
Frame Outside Diameter8.70 in
Driver Displacement0.13 cu ft
Driver Warranty2 Year Limited, Authorized Dealer Purchase, Original Owner
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

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

Handcrafted in USA

Hand-assembled at our facility in Tullahoma, TN. Every enclosure is inspected before it ships.

Tuned to the Build

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.

Frequently Asked Questions

Why is this enclosure tuned to 32.5 Hz?

Why is this a Professional build and not a Performance Optimized box?

Threaded inserts or a kit?

Do I need a subsonic filter?

Would a sealed box be better for me?

How does the front port work?

What does the price cover, and how does it ship?

Is the X-Series v.3 8" X-8 included?

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