Proline X PO 10-S W KXE sealed wedge, front baffle with gloss black insert and pre-wired leads, 20.4 by 13 inches.

Proline X

Performance Optimized Wedge Sealed 10" Enclosure | Focal SUB 25 KXE

Q: Does this fit the Focal SUB 25 KXE, and will any other 10 inch fit?

The SUB 25 KXE, yes. The baffle is cut to 9.30 in (236 mm). Loudspeaker Database lists a 235 mm cutout, but Focal's own drawing puts the basket at 235.2 mm just under the flange, which a 235 mm hole would not pass; the 236 mm cut clears it and the 268 mm frame still covers it with margin. The 6.77 inch motor clears the cabinet with 0.75 inch to spare, and the KXE ships in one version, dual 4 ohm, so there is no coil variant to choose.Any other 10, no. The airspace is engineered around the KXE's 0.52 Qts and 20 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 0.83 cubic feet, and what alignment does it target?

It is the Butterworth volume on Focal's published Fs 38 Hz, Qts 0.52 and Vas 20 liters: system Qtc 0.707, maximally flat, with resonance and half power both at 51.7 Hz. Focal's own closed-box simulations for this driver run at 16 and 30 liters, and this volume sits between them.One caveat on Focal's sheet: its moving mass and resonance imply a Vas nearer 16 liters than the printed 20. If that is the truer figure, this cabinet reads Qtc 0.67 instead, a touch more damped. 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 25 KXE at 600 watts RMS and 1200 watts maximum, so target 420 to 600 watts RMS at the final load.The SUB 25 KXE carries two 4 ohm voice coils (3.2 ohms DC each): wire them in parallel for a nominal 2 ohm load or in series for 8 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 driver fires 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 51.7 Hz on this page.

Q: Why is the front baffle double-layered?

The baffle is two bonded 3/4 inch sheets, 1.5 inches through. The KXE moves 736 cubic centimeters of air at its 22.5 mm excursion limit, and a single 3/4 inch panel flexes under that load, which smears output and works the driver loose over time.The outer layer is machined as a flush recess to Focal's 10.55 inch frame, so the driver bolts to the inner layer and sits flush with the gloss black acrylic insert.

Q: What is the expected low-frequency extension?

Anechoic F3 is 51.7 Hz with system resonance at 51.7 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 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 0.83 cubic feet 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, 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 25 KXE, so you set the driver in the recess, mark its holes, drill and press the inserts. The Focal SUB 25 KXE is purchased separately, and the cabinet is cut direct fit to it, not a general purpose 10 inch box.

SKU: PO 10-S W KXE BB

QUICK SPECS

Best For: Focal SUB 25 KXE Trunk-Fit Builds
Net Volume: 0.83 cu ft (0.95 cu ft Gross)
Driver Match: Focal SUB 25 KXE (dual 4 ohm)
Construction: Rear-Firing Wedge | V-Groove/Dado | Double 1.5" Baffle | Threaded 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.

$ 269.99

Acrylic Insert Color

In Stock and Ready to Ship

Financing available. Choose Shop Pay Installments at checkout.

Performance Optimized Wedge Sealed 10" Enclosure | Focal SUB 25 KXE

Enclosure Type Sealed

External Dimensions 20.38" W x 13" H x 13.34" D at base tapering to 8.61" D at top

Gross Volume 0.95 cu ft

Net Volume 0.83 cu ft

Shipping Weight 33 lbs

Front Panel Thickness 1.5"

INSTALLER'S TAKE

Built to the KXE's Butterworth volume on Focal's figures, 0.83 cubic feet, Qtc 0.707. If Vas is really 16 liters, as the moving mass suggests, it reads 0.67. Either way it is flat, not boomy.

The 6.77 inch motor is deep for a 10; it sets the top of the wedge at 8.61 and clears with 0.75 to spare. That is why this wedge is slightly deeper than it is tall.

Cutout is 9.30, not the 235 mm Loudspeaker Database lists: Focal's own drawing puts the basket at 235.2 mm, so a 235 mm hole would not take it. The 268 mm frame covers 9.30 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 | Focal SUB 25 KXE

10" Sealed Wedge Enclosure | Rear-Firing Trunk-Load Design

0.83 ft3 Net0.95 ft3 GrossQtc 0.71Single Chamber Wedge20.38" x 13" x 8.61/13.34"Built in Tennessee

The Focal SUB 25 KXE in a Sealed Wedge

The SUB 25 KXE is the 10 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, 600 watts RMS and 1200 watts maximum, and 22.5 mm of one-way excursion, which moves 736 cubic centimeters of air at the limit, a great deal for a 10. It is also deep for its size, 6.77 inches of mounting depth on a 10.55 inch frame. Every figure comes from Focal's own SUB 25 KXE technical sheet. One number on it is soft: Focal prints 20 liters of Vas and runs its own closed-box simulations on it, but the published moving mass and resonance imply nearer 16 liters. At 16 the Qtc in this cabinet would read 0.67 instead of 0.71, so treat the alignment as a range a few hundredths wide.

0.83 cubic feet net is the Butterworth volume on Focal's published Fs 38 Hz, Qts 0.52 and Vas 20 liters: Qtc 0.707, maximally flat, with system resonance and half power both at 51.7 Hz. Focal's own closed-box simulations for this driver run at 16 and 30 liters (0.57 and 1.06 cubic feet); this volume sits between them.

Trunk-Load Wedge Design Explained

The driver mounts on the vertical trunk-lid-side face and fires 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 the Focal SUB 25 KXE

Half power lands at 51.7 Hz anechoic, before any cabin gain. Focal publishes the cone area outright, 327 square centimeters, and the driver displacement, 3 liters, which is already taken out of the net figure.

Alignment Numbers

Driver	System Qtc	fc	F3
SUB 25 KXE, dual 4 ohm	Qtc 0.707	51.7 Hz	51.7 Hz

Mounting Geometry

The baffle is cut to 9.30 in (236 mm). Loudspeaker Database lists a 235 mm cutout, but Focal's own drawing puts the basket at 235.2 mm just under the flange, which a 235 mm hole would not pass; the 236 mm cut clears it and the 268 mm frame still covers it with margin. The rear panel rakes 20 degrees, so the cavity deepens from 8.61 in at the top to 13.34 in at the base, and the 6.77 in motor clears it with 0.75 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 brace 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 38 Hz, Qts 0.52, Qes 0.58, Qms 5.0, Vas 20 L, Sd 327 cm2, Mms 163 g, Cms 0.12 mm/N, Bl 21.5 N/A, Re 6.4 ohm with the coils in series. Sensitivity 84.5 dB at 2.83 V.

Wiring the Focal SUB 25 KXE to Your Amplifier

The SUB 25 KXE carries two 4 ohm voice coils (3.2 ohms DC each): wire them in parallel for a nominal 2 ohm load or in series for 8 ohms. Confirm the final load against your amplifier's minimum stable impedance before powering the system.

Power handling is 600 watts RMS per driver. Aim for roughly 420 to 600 watts 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 pre-wired terminal cup, 12 gauge OFC to the driver position. Polyfill wall lining installed. Threaded insert kit and stainless machine screws in the box. 1 year limited warranty. Enclosure only, the driver is purchased separately. Call or text 931-563-5151.

Focal SUB 25 KXE: Built to a Butterworth Alignment

0.83 cubic feet net at Qtc 0.707, F3 51.7 Hz, cut direct fit and built to order in Tennessee.

Specifications

Specification	Value
Series	Proline X Performance Optimized Wedge
Compatible Driver	Focal SUB 25 KXE (K2 Power), quantity 1. Direct fit
Configuration	Single 10 inch, single chamber 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	20.38 in
External Height	13 in at the seat face
External Depth	13.34 in at the base, tapering to 8.61 in at the top
Internal Volume, Gross	0.95 cu ft
Internal Volume, Net Acoustic	0.83 cu ft after the brace and Focal's published 3 L displacement
Driver Mounting Depth	6.77 in required; 0.75 in clearance above the motor against the raked rear panel
Alignment	Qtc 0.707, fc 51.7 Hz, F3 51.7 Hz anechoic; about 0.67 if Vas is 16 L rather than Focal's 20
Focal Closed-Box Simulations	16 L (Qtc 0.80) and 30 L (Qtc 0.68), Focal technical sheet
Woofer Opening	9.30 in (236 mm); clears the 235.2 mm basket on Focal's drawing
Frame Outer Diameter	10.55 in (268 mm), Focal drawing
Bolt Circle	Not printed by Focal; threaded insert kit included
Driver Displacement	3 L / 0.11 cu ft, published by Focal
Fs / Qts / Qes / Qms	38 Hz / 0.52 / 0.58 / 5.0
Vas / Mms / Cms / Bl	20 L / 163 g / 0.12 mm/N / 21.5 N/A
Driver Sd	327 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	84.5 dB at 2.83 V / 1 m, Focal spec
Driver Power Handling	600 W RMS / 1200 W maximum
Wiring Options	Dual 4 ohm coils: 2 ohm in parallel, 8 ohm in series
Voice Coil	65 mm dual 4 ohm, CCAW on a glass fiber former, 4 layers
Parameter Source	Focal SUB 25 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	Windowed brace, dadoed to the shell
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
Acrylic Insert	Gloss black acrylic baffle insert standard; None variant minus $20
Damping	Light polyfill wall lining, does not alter acoustic volume
Carpet	Plush black
Shipping Weight	33 lb
Warranty	1 Year Limited
Built In	Tullahoma, Tennessee

Performance Graphs

Net airspace

0.83

cu ft

System Qtc

0.71

sealed

Half power

51.7

Hz · F3

Xmax at

936

W RMS · no filter

With 25 Hz subsonic

1180

W RMS · +26%

Amplifier

600

W RMS recommended

This enclosure holds 0.83 cu ft net . In it the Focal SUB 25 KXE runs a system Qtc of 0.71 with half power at 51.7 Hz, and the cone reaches its 22.5 mm travel limit at 936 W, above the driver’s 600 W thermal rating, so heat stops you before travel does. Run a subsonic filter at 25 Hz and that becomes 1180 W — +244 W, or 26 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 = 65.5

dual 4 ohm, coils in series · EBP 65.5

At 65.5 the SUB 25 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

0.83 cu ft against a 20.0 L Vas.

α = Vas ÷ Vb = 0.85 · Fc = Fs√(α+1) = 52 Hz · Qtc = 0.71

dual 4 ohm, coils in series · Qtc 0.71, Fc 52 Hz, F3 51.7 Hz

The box lifts resonance from 38.0 Hz free-air to 52 Hz and half power lands at 51.7 Hz, anechoic, before any cabin gain. Figures are Focal’s own SUB 25 KXE technical sheet. Vas is the one soft number: Focal prints 20 liters and its own closed-box simulations use it, while the published moving mass and resonance imply nearer 16; at 16 liters every Qtc on this page would read a few hundredths lower. 0.83 cubic feet is the Butterworth volume on Focal’s figures. The dual wedge and the dual down fire hold the same per chamber, so these numbers describe them too.

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 = 936 W unfiltered → 1180 W with a 25 Hz subsonic

dual 4 ohm, coils in series · 936 W, no filterdual 4 ohm, coils in series · 1180 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 936 W, reached first at 20 Hz. It sits above the 600 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 1180 W before hitting the same 22.5 mm. That is 26 percent more amplifier for the price of one filter setting.

Param	Value	Unit	Note
Fs	38.00	Hz	free-air resonance
Qts	0.520		dual 4 ohm, coils in series
Vas	20.00	L	equivalent compliance
Sd	327.0	cm²	effective piston area
Xmax	22.5	mm	one-way linear travel
Pe	600	W	continuous RMS
SPL	84.6	dB	1 W / 1 m, derived from T/S

Driver parameters as published by Focal SUB 25 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.