Pro 8D-P X8 placeholder
Pro 8D-P X8 placeholder

Proline X

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

SKU: Pro 8D-P X8

QUICK SPECS
  • Alignment: 2.18 cu ft net vented at 33.0 Hz. F3 28.4 Hz anechoic, 3.65 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, 40.6 sq in front slot port beside the woofer with one bend along the back wall, port and excursion gated at 1600 W
  • Cabinet: 34.00" W x 14.00" H x 17.50" D, 59 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.
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Advanced Terminal Cup Built in-house. ABS/Carbon Fiber. Stainless steel hardware. Copper ring terminals.
$ 525.99
In Stock and Ready to Ship
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Pro 8D-P X8 placeholder

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

Regular price $ 525.99
Sale price $ 525.99 Regular price
Unit price
Enclosure Type Ported
External Dimensions 34.00" W x 14.00" H x 17.50" D
Gross Volume 3.41 cu ft
Net Volume 2.18 cu ft
Tuning Frequency 33.0 Hz
Port Area 40.6 Square Inches
Weight 59 lbs
INSTALLER'S TAKE

I built this one for a pair of X-Series v.3 8" X-8 in a single shared chamber, which is how a dual ported box should be built: one volume, one port, both drivers loading the same air.

It gets the full Professional treatment, a 2.25 inch three-layer baffle with both woofers flush mounted in the outer layer, and the port on the left of the face.

Wiring is where a dual bites you. These are two 2 ohm coils each, so you can land on 1 ohm with all four coils in parallel, 2 ohms as two series pairs in parallel, or 8 ohms with everything in series. Check what your amplifier is rated for before you wire it, not after.

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.

It ships dry. Do not add polyfill to a ported box. Set your subsonic filter at 26 Hz.

Product Details
Enclosure Specifications
Performance Graphs
Woofer Details
Materials
Product Details

Proline X Professional 8" Ported

A ported eight inch box for a pair of X-Series v.3 8" X-8, one shared chamber vented at 33.0 Hz

2.18 cu ft net Tuned 33.0 Hz F3 28.4 Hz 2.25" three-layer baffle Cut for the X-Series v.3 8" X-8 Built in Tennessee
2.18cu ft net
33.0Hz tuning
28.4Hz F3 anechoic
40.6sq in port area

Why this driver is vented at 33.0 Hz

This cabinet holds two X-Series v.3 8" X-8 in 2.177 cubic feet net, vented at 33.0 Hz through a 40.6 square inch port. F3 lands at 28.4 Hz with 3.65 dB of passband ripple. It measures 34.00 inches wide, 14.00 tall and 17.50 deep.

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 two kits, one per woofer.

Both drivers share one chamber and one port rather than sitting in separate boxes, so the pair works against the whole volume and the port is sized for the pair rather than doubled. The port carries 40.6 square inches of area at 33.0 Hz, and the design power for the velocity and excursion checks is 1600 W for the pair. Passband ripple holds at 3.65 dB across the tuning, with F3 at 28.4 Hz.

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 1600 W

The 40.6 square inch slot beside the woofer is sized so the channel runs 23.4 metres per second and the mouth 16.6 metres per second at the driver's rated power, under the 17 metres per second where a slot starts to chuff. The channel runs 10.50 inches along its wall and turns once along the back wall for another 18.29 inches, which is why a 33.0 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 40.6 square inches and holds the mouth at 16.6 metres per second at 1600 W.

What the price covers

Every Professional cabinet is priced the same way, by its size: this one is 4.82 cubic feet outside. Delivery to the 48 states is inside the price; it ships as a 59 lb parcel and checkout adds nothing. The Performance Optimized 8 inch ported wedge is $329.99. The $196 difference is the larger box and the port this driver needs to run at its rating.

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 2.18 cubic feet net and tunes to 33.0 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

34.00" W x 14.00" H x 17.50" D external. A windowed brace runs front to back beside the woofer, clearing the cutout by two and a half inches. The box ships dry: polyfill detunes a ported alignment. This is our dual 8 inch Professional envelope, built around the X-Series v.3 8" X-8's own frame and mounting depth, with both woofers on one face and the port on the left. It ships as a parcel.

Port mouth velocity peaks at 16.6 m/s against the 17 m/s point where a slot begins to chuff, and 23.4 m/s in the channel, both measured at the pair's design power. Both drivers must be the same model and the same coil: mixing them puts unequal loads on one shared chamber, and neither driver sees the airspace it was picked for. 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 two kits, one per woofer.

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 1600 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 Width34.00 Inches
External Height14.00 Inches
External Depth17.50 Inches
Internal Volume (Gross)3.41 Cubic Feet
Internal Volume (Net After Displacement)2.18 Cubic Feet
Port TypeVertical Slot Beside The Woofer | Front Exit | One 90 Degree Bend Along The Back Wall
Port Geometry3.25 x 12.50 Inches, 40.6 Square Inches, 35.79 Inches Of Path
Port Area40.6 Square Inches
Port Tuning (Fb)33.0 Hz
Port Mouth1/2 In Roundover On All Four Edges, 57.4 Square Inches At The Face
Port Air Velocity23.4 m/s In The Channel, 16.6 m/s At The Mouth, At 1600 W (17.0 m/s Chuff Threshold)
Design Power Basis1600 W RMS (1.2 x The Driver Rating) For Port Velocity And Excursion
Predicted F328.4 Hz (Anechoic)
Passband Ripple3.65 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 / Windowed Brace Front To Back Beside 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
Weight59 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
2.18
cu ft
Tuning
33.0
Hz · Fb
Half power
28.4
Hz · F3, anechoic
Xmax at
2292
W RMS · 26 Hz subsonic
With NO filter
1112
W RMS · unfiltered
Port
16.6
m/s at the mouth · 1600 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

2.18 cu ft net against a 3.9 L Vas, vented at 33.0 Hz.

Fb = 33.0 Hz  ·  F3 = 28.4 Hz  ·  passband ripple 3.65 dB
20 30 50 70 100 150 200 +16 +12 +8 +4 0 −4 −8 −12 −16 −20 −24 −28 FREQUENCY · Hz LEVEL · dB −3 dB Fb 33.0
Sundown Audio X-Series v.3 8" X-8 D2 · Fb 33.0 Hz, F3 28.4 Hz
Anechoic, before any cabin gain, with the 26 Hz subsonic filter already applied. The vent takes over below 33 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 publish no sealed volume for it — 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 = 2292 W with a 26 Hz subsonic  ·  1112 W with none  →  the filter is worth 2.1×
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 2292 W reaches Xmax here
2292 W · subsonic at 26 Hz, 24 dB/oct1112 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 2292 W, reached first at 29 Hz. Take the filter away and the same cabinet reaches 19.0 mm on 1112 W — the filter is worth 2.1× 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 1112 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 cabinet takes two of them in one shared chamber, so both drivers see the same air and the same port. Each opening 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 33.0 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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