Proline X PO 12D-S W KXE sealed wedge, front baffle with gloss black insert and pre-wired leads, 32 by 16 inches.

Proline X

Performance Optimized Wedge Sealed Dual 12" Enclosure | Focal SUB 30 KXE

Q: Does this fit the Focal SUB 30 KXE, and will any other 12 inch fit?

The SUB 30 KXE, yes. The baffle is cut to 11.23 in (285 mm). Loudspeaker Database lists a 284 mm cutout, but Focal's own drawing puts the basket at 284.2 mm just under the flange, which a 284 mm hole would not pass; the 285 mm cut clears it and the 318 mm frame still covers it with margin. The 6.77 inch motor clears the cabinet with 4.35 inch to spare, and the KXE ships in one version, dual 4 ohm, so there is no coil variant to choose. Run two so the chambers match.Any other 12, no. The airspace is engineered around the KXE's 0.46 Qts and 50 liters of Vas, and a different woofer that happened to drop into the hole would not see the alignment printed on this page.

Q: Why 1.25 cubic feet per chamber, and what alignment does it target?

It sits just under the 1.30 cubic foot Butterworth volume on Focal's published Fs 29 Hz, Qts 0.46 and Vas 50 liters, which keeps the cabinet to 17.44 inches deep at the base: system Qtc 0.714, a hair above maximally flat, with resonance at 45.0 Hz and half power at 44.6 Hz. Focal's own closed-box response chart for this driver is drawn at 25 and 35 liters, and this volume sits at the larger of the two.One caveat on Focal's sheet: its moving mass and resonance imply a Vas nearer 58 liters than the printed 50. If that is the truer figure, this cabinet reads Qtc 0.75 instead, a touch livelier. Either way it is a well-behaved sealed alignment.

Q: What amplifier power should I run, and how should I wire it?

Focal rates the SUB 30 KXE at 800 watts RMS per driver and 1600 watts maximum, so target 560 to 800 watts RMS per driver at the final load.Each SUB 30 KXE carries two 4 ohm voice coils (3.2 ohms DC each): series for 8 ohms, parallel for 2. Wire both drivers identically. Each driver in series with the pair in parallel gives 4 ohms, the safe load on any amplifier; each driver in parallel with the pair in series also gives 4; all four coils in parallel is 1 ohm and needs an amplifier rated for it; all in series is 16 ohms. Confirm your amplifier's minimum stable impedance first.

Q: Why the wedge angle, and why rear-firing into the trunk?

The seat-side face carries a 20 degree rake that matches the lean of a factory rear seat back, so the cabinet sits flush against it and the cargo space in front stays usable. The baffle is the vertical trunk-lid-side face, so the drivers fire rearward into the trunk cavity.The trunk acts as an acoustic extension for the sealed box, and the cabin adds real output below 50 Hz, so in-vehicle response runs deeper than the anechoic 44.6 Hz on this page.

Q: Why two separate chambers instead of one shared volume?

Two drivers sharing one sealed volume load each other: each driver's compression stroke becomes the pressure the other works against, which blurs the alignment either would have alone. A bonded full-height 3/4 inch divider gives each driver its own 1.25 cubic feet and its own polyfill.It also means a failure in one driver does not unload the other, and the alignment on this page is the alignment in each chamber, not an average across a shared box.

Q: What is the expected low-frequency extension?

Anechoic F3 is 44.6 Hz per chamber with system resonance at 45.0 Hz. At Qtc 0.71 the response is maximally flat into the rolloff, so F3 and fc coincide.Those figures exclude cabin gain. In a car the cabin's transfer function adds real output below 50 Hz, so in-vehicle response runs deeper than the numbers above.

Q: Do I need to add polyfill or damping?

No. Polyfill is already installed in both chambers as a light wall lining to control internal reflections, and the quantity is chosen so it does not change the acoustic volume.Do not add more. Packing a sealed box with fill makes it behave as though it were larger, which walks the alignment away from the 1.25 cubic feet per chamber this cabinet was built to.

Q: Is the driver included, and are the threaded inserts installed?

No driver. This is an enclosure only. You receive the cabinet finished in plush black carpet with the gloss black acrylic baffle insert, one side-mounted pre-wired terminal cup to both positions, the polyfill lining already in place, and a threaded insert kit with stainless machine screws.The inserts ship loose on purpose: Focal prints no bolt circle for the SUB 30 KXE, so you set the driver in the recess, mark its holes, drill and press the inserts. The pair of Focal SUB 30 KXE is purchased separately, and the cabinet is cut direct fit to it, not a general purpose 12 inch box.

SKU: PO 12D-S W KXE BB

QUICK SPECS

Best For: Dual Focal SUB 30 KXE Trunk-Fit Builds
Net Volume: 1.25 cu ft per chamber (2.85 cu ft Gross Total)
Driver Match: Pair of Focal SUB 30 KXE (dual 4 ohm), matched
Construction: Dual Chamber | Rear-Firing Wedge | V-Groove/Dado | Double 1.5" Baffle | 1 Shared Terminal Cup | Insert Kit

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.

$ 389.99

Acrylic Insert Color

In Stock and Ready to Ship

Financing available. Choose Shop Pay Installments at checkout.

Performance Optimized Wedge Sealed Dual 12" Enclosure | Focal SUB 30 KXE

Enclosure Type Sealed

External Dimensions 32.00" W x 16" H x 17.44" D at base tapering to 11.62" D at top

Gross Volume 2.85 cu ft

Net Volume 2.50 cu ft

Shipping Weight 60 lbs

Front Panel Thickness 1.5"

INSTALLER'S TAKE

Built at 1.25 cubic feet per chamber, just under the KXE's 1.30 Butterworth volume, to keep the base at 17.44 inches: Qtc 0.714. If Vas is really nearer 58 liters, as the moving mass suggests, it reads 0.75. Either way it is flat, not boomy.

Two chambers at 1.25 each, pinned at the 32 inch cap, 16 tall, 17.44 at the base. Wire the pair identically; each driver in series and the pair in parallel is 4 ohms.

Cutout is 11.23, not the 284 mm Loudspeaker Database lists: Focal's own drawing puts the basket at 284.2 mm, so a 284 mm hole would not take it. The 318 mm frame covers 11.23 fine.

Inserts ship in the kit, not pressed: Focal prints no bolt circle. Mark from the driver, drill, press. If we get the hole pattern later this changes to pre-installed.

Product Details

Performance Optimized Wedge | Dual Focal SUB 30 KXE

Dual 12" Sealed Wedge Enclosure | Rear-Firing Trunk-Load Design

1.25 ft3 Net per Chamber2.85 ft3 GrossQtc 0.71Two Separate Chambers32.00" x 16" x 11.62/17.44"Built in Tennessee

A Pair of Focal SUB 30 KXE in a Sealed Wedge

The SUB 30 KXE is the 12 inch of Focal's K2 Power line: an aramid-fiber K2 sandwich cone on a butyl surround, a 65 mm dual 4 ohm voice coil, 800 watts RMS and 1600 watts maximum, and 22.5 mm of one-way excursion, which moves 1130 cubic centimeters of air at the limit, well past a typical 12. It carries the same deep motor as the 10 inch KXE, 6.77 inches of mounting depth on a 12.52 inch frame. Every figure comes from Focal's own SUB 30 KXE technical sheet. One number on it is soft: Focal prints 50 liters of Vas and draws its closed-box response chart on it, while its own compliance implies 52.5 and the published moving mass and resonance nearer 58 liters. At 58 the Qtc in this cabinet would read 0.75 instead of 0.71, so treat the alignment as a range a few hundredths wide.

1.25 cubic feet net per chamber sits just under the 1.30 cubic foot Butterworth volume on Focal's published Fs 29 Hz, Qts 0.46 and Vas 50 liters: Qtc 0.714, a hair above maximally flat, with system resonance at 45.0 Hz and half power at 44.6 Hz. Focal's own closed-box response chart for this driver is drawn at 25 and 35 liters (0.88 and 1.24 cubic feet); this volume sits at the larger of the two.

Two Fully Separate Chambers

A bonded full-height 3/4 inch MDF divider splits the cabinet into two sealed chambers of 1.25 cubic feet net each, so every driver sees exactly the airspace it would have in the single wedge. Two drivers sharing one volume load each other; the divider removes that, and each chamber carries its own polyfill.

The cabinet is pinned at the 32 inch dual width cap, 16 inches tall, 11.62 inches deep at the top and 17.44 at the base, with the depth absorbing the airspace. One shared side-mounted terminal cup feeds both driver positions.

Trunk-Load Wedge Design Explained

The drivers mount on the vertical trunk-lid-side face and fire rearward into the trunk cavity.

Seat-Side Face Matches Seat Lean

Angled face matches the roughly 20 degree factory seat lean.

Trunk-Lid-Side Face Fires the Woofer

Vertical baffle, cone firing rearward into the trunk cavity.

Trunk Cavity Loading

The trunk acts as an acoustic extension for a smoother presentation.

Preserves Trunk Cargo Space

The wedge tucks against the seat back and the space in front stays usable.

Engineered for a pair of Focal SUB 30 KXE

Half power lands at 44.6 Hz anechoic, before any cabin gain. Focal publishes the cone area outright, 502 square centimeters, and the driver displacement, 4 liters, which is already taken out of the net figure.

Alignment Numbers (Per Chamber)

Driver (per chamber)	System Qtc	fc	F3
SUB 30 KXE, dual 4 ohm	Qtc 0.714	45.0 Hz	44.6 Hz

Mounting Geometry

The baffle is cut to 11.23 in (285 mm). Loudspeaker Database lists a 284 mm cutout, but Focal's own drawing puts the basket at 284.2 mm just under the flange, which a 284 mm hole would not pass; the 285 mm cut clears it and the 318 mm frame still covers it with margin. The rear panel rakes 20 degrees, so the cavity deepens from 11.62 in at the top to 17.44 in at the base, and the 6.77 in motor clears it with 4.35 in to spare. Focal's drawing shows eight mounting holes but prints no bolt circle, so the baffle ships undrilled with a threaded insert kit and stainless machine screws: set the driver in the recess, mark its holes, drill, press the inserts and bolt it down.

What the Numbers Rest On

Langboard Elite MDF

Premium 3/4 in MDF throughout.

V-Groove and Dado Joinery

CNC cut V-grooves at every panel intersection, sides and divider seated in dados.

Double-Layer 1.5" Front Baffle

Two bonded 3/4 in MDF sheets at the driver face, the outer layer machined as a flush recess.

Focal's Own Sheet

Fs 29 Hz, Qts 0.46, Qes 0.49, Qms 6.1, Vas 50 L, Sd 502 cm2, Mms 183 g, Cms 0.15 mm/N, Bl 21.3 N/A, Re 6.4 ohm with the coils in series. Sensitivity 86.5 dB at 2.83 V.

Wiring a pair of Focal SUB 30 KXE to Your Amplifier

Each SUB 30 KXE carries two 4 ohm voice coils (3.2 ohms DC each): series for 8 ohms, parallel for 2. Wire both drivers identically. Each driver in series with the pair in parallel gives 4 ohms, the safe load on any amplifier; each driver in parallel with the pair in series also gives 4; all four coils in parallel is 1 ohm and needs an amplifier rated for it; all in series is 16 ohms. Confirm the final load against your amplifier's minimum stable impedance before powering the system.

Power handling is 800 watts RMS per driver, 1600 across the pair. Aim for roughly 560 to 800 watts per driver at the impedance you wire.

Built in Tennessee, Backed by Audio Intensity

Cut and assembled in Tullahoma, Tennessee on our own CNC equipment. Finished in plush black carpet with the gloss black acrylic baffle insert, one shared pre-wired terminal cup, 12 gauge OFC to both driver positions. Polyfill wall lining installed. Threaded insert kit and stainless machine screws in the box. 1 year limited warranty. Enclosure only, the drivers are purchased separately. Call or text 931-563-5151.

Dual Focal SUB 30 KXE: Built to a Butterworth Alignment

1.25 cubic feet net per chamber at Qtc 0.714, F3 44.6 Hz, cut direct fit and built to order in Tennessee.

Specifications

Specification	Value
Series	Proline X Performance Optimized Wedge
Compatible Driver	Focal SUB 30 KXE (K2 Power), quantity 2. Direct fit
Configuration	Dual 12 inch, two separate chambers, sealed wedge
Mounting Position	Trunk or cargo area, tall face against the rear seat back
Firing Direction	Rearward into the trunk. Not a down fire design, no feet included
External Width	32.00 in, the dual width cap
External Height	16 in at the seat face
External Depth	17.44 in at the base, tapering to 11.62 in at the top
Internal Volume, Gross	2.85 cu ft total
Internal Volume, Net Acoustic	1.25 cu ft per chamber after the divider and Focal's published 4 L displacement per driver
Driver Mounting Depth	6.77 in required; 4.35 in clearance above the motor against the raked rear panel
Alignment per chamber	Qtc 0.714, fc 45.0 Hz, F3 44.6 Hz anechoic; about 0.75 if Vas is 58 L rather than Focal's 50
Focal Closed-Box Chart	Drawn at 25 L and 35 L, Focal technical sheet
Woofer Opening	11.23 in (285 mm), two; clears the 284.2 mm basket on Focal's drawing
Frame Outer Diameter	12.52 in (318 mm), Focal drawing
Bolt Circle	Not printed by Focal; threaded insert kit included
Driver Displacement	4 L / 0.14 cu ft, published by Focal
Fs / Qts / Qes / Qms	29 Hz / 0.46 / 0.49 / 6.1
Vas / Mms / Cms / Bl	50 L / 183 g / 0.15 mm/N / 21.3 N/A
Driver Sd	502 cm2, published by Focal
Xmax	22.5 mm one way, Focal spec
DC Resistance	3.2 + 3.2 ohm (6.4 ohm in series)
Driver Sensitivity	86.5 dB at 2.83 V / 1 m, Focal spec
Driver Power Handling	800 W RMS / 1600 W maximum per driver
Wiring Options	Dual 4 ohm coils: 2 ohm in parallel, 8 ohm in series; two drivers give 1, 4 or 16 ohm, see the wiring section
Voice Coil	65 mm dual 4 ohm, CCAW on a glass fiber former, 4 layers
Parameter Source	Focal SUB 30 KXE technical sheet, v1 29/09/2023
Material	Langboard Elite MDF
Construction	CNC cut, V-groove and dado joinery
Panel Thickness	0.75 in
Front Baffle	1.5 in double baffle, outer layer machined as a flush recess
Internal Bracing	Full-height 3/4 in divider
Driver Mounting	Threaded insert kit included, NOT pre-installed: Focal prints no bolt circle
Terminal Cups	One Proline X ABS and carbon fiber composite, side mounted, pre wired 12 gauge OFC to both driver positions
Acrylic Insert	Gloss black acrylic baffle insert standard; None variant minus $20
Damping	Light polyfill wall lining in both chambers, does not alter acoustic volume
Carpet	Plush black
Shipping Weight	60 lb
Warranty	1 Year Limited
Built In	Tullahoma, Tennessee

Performance Graphs

Net airspace

1.25

cu ft per chamber

System Qtc

0.71

sealed

Half power

44.6

Hz · F3

Xmax at

976

W RMS · no filter

With 25 Hz subsonic

1329

W RMS · +36%

Amplifier

800

W RMS recommended

This enclosure holds 1.25 cu ft net per chamber. In it the Focal SUB 30 KXE runs a system Qtc of 0.71 with half power at 44.6 Hz, and the cone reaches its 22.5 mm travel limit at 976 W, above the driver’s 800 W thermal rating, so heat stops you before travel does. Run a subsonic filter at 25 Hz and that becomes 1329 W — +352 W, or 36 percent more power for the same 22.5 mm of travel.

01Is it a sealed driver?

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

EBP = Fs ÷ Qes = 59.2

dual 4 ohm, coils in series · EBP 59.2

At 59.2 the SUB 30 KXE sits in the transition band, not the sealed band. That is not a mismatch: a transition motor works in either alignment, and sealed buys a smaller box and a gentler roll-off at the cost of some low-end output. Stage 02 shows what this airspace actually does with it.

02What the box does to it

1.25 cu ft against a 50.0 L Vas.

α = Vas ÷ Vb = 1.41 · Fc = Fs√(α+1) = 45 Hz · Qtc = 0.71

dual 4 ohm, coils in series · Qtc 0.71, Fc 45 Hz, F3 44.6 Hz

The box lifts resonance from 29.0 Hz free-air to 45 Hz and half power lands at 44.6 Hz, anechoic, before any cabin gain. Figures are Focal’s own SUB 30 KXE technical sheet. Vas is the one soft number: Focal prints 50 liters and draws its closed-box chart on it, while its own compliance implies 52.5 and the moving mass and resonance nearer 58; at 58 liters every Qtc on this page would read a few hundredths higher. Each chamber of this dual holds 1.25 cubic feet, just under the 1.30 Butterworth box, which keeps the cabinet to 17.44 inches deep at the base.

03The 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 22.5 mm — and a bigger one once a subsonic filter stops it wasting travel below the passband.

P_Xmax = 976 W unfiltered → 1329 W with a 25 Hz subsonic

dual 4 ohm, coils in series · 976 W, no filterdual 4 ohm, coils in series · 1329 W with subsonic at 25 Hz, 24 dB/octXmax 22.5 mm one-way

Every trace touches the limit and no further, because each is drawn at the exact power that puts that coil on 22.5 mm. Unfiltered that is 976 W, reached first at 20 Hz. It sits above the 800 W the driver can take thermally, so the voice coil gives up before the suspension does. The dashed traces are the same driver behind a subsonic filter at 25 Hz, 24 dB/oct: stopping the cone wasting travel below the passband lets it take 1329 W before hitting the same 22.5 mm. That is 36 percent more amplifier for the price of one filter setting.

Param	Value	Unit	Note
Fs	29.00	Hz	free-air resonance
Qts	0.460		dual 4 ohm, coils in series
Vas	50.00	L	equivalent compliance
Sd	502.0	cm²	effective piston area
Xmax	22.5	mm	one-way linear travel
Pe	800	W	continuous RMS
SPL	85.8	dB	1 W / 1 m, derived from T/S

Driver parameters as published by Focal SUB 30 KXE technical sheet. Curves computed against this enclosure’s actual net airspace.

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, 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 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.