Proline X
Performance Optimized Down Fire Wide Sealed 12" Enclosure | Focal SUB 30 KXE
SKU: PO 12-S DFW KXE
- Alignment: 1.539 cu ft net. Qtc 0.674, Fc 42.5 Hz, F3 44.7 Hz
- Down Fire Wide: 41"W x 14"D x 8.3125"H in down fire position, lower than the standard 30 x 15 (8.99 in)
- Height Set By: the 6.77 in motor, 0.75 in clearance above it; holds more air than the standard box, so Qtc is lower
- Driver: Focal SUB 30 KXE, 800 W RMS, 22.5 mm Xmax, 6.77 in mounting depth
- Standoffs: Included, 1.75 in, shipped uninstalled. Installed height near 10.0625 in
Financing available. Choose Shop Pay Installments at checkout.
Performance Optimized Down Fire Wide Sealed 12" Enclosure | Focal SUB 30 KXE
More enclosures cut for Focal subwoofers: Focal Subwoofer Boxes
Proline X Performance Optimized Down Fire Wide 12" Sealed
Cut for the Focal SUB 30 KXE
The Down Fire Wide Format
Down Fire Wide is the same driver in a different shape. The standard Performance Optimized Down Fire cabinet for the Focal SUB 30 KXE is 30 by 15 inches. This one runs 41 inches wide by 14 inches deep: 1 inch shallower front to back and 11 inches longer.
Fourteen inches is not arbitrary. A 12 inch frame needs about 13 inches of baffle to sit on, so 14 is the practical minimum depth for this driver size. The Focal SUB 30 KXE frame measures 12.52 inches across and sits on the 14 inch deep baffle with about 0.74 inches of baffle fore and aft.
Spreading the airspace along 41 inches instead of 30 means the cabinet does not have to climb to find it. This box stands 8.3125 inches tall, against 8.99 for the standard 30 x 15 Focal SUB 30 KXE cabinet, both measured in the down fire position without feet. That is 0.6775 inches lower.
Which one to choose. The standard 30 x 15 is the pick when length is limited. This one is the pick when height or depth is the limit and you have 41 inches of run. Plan around the installed height: the 1.75 inch standoffs put the finished stack near 10.0625 inches.
Performance, Performance Optimized, and Micro
Proline X builds three tiers of Down Fire enclosure. The difference is not finish or materials, it is whether the cabinet was designed for a category or for a driver, and how much of the fitting work is already done for you.
| Performance | Performance Optimized | Micro Series | |
|---|---|---|---|
| Fitment | Universal. Accepts any subwoofer that clears the published cutout and mounting depth. | Woofer specific. Cut for one named subwoofer, with cutout, mounting depth, magnet clearance and displacement drawn in CAD from that driver. | Woofer specific. Cut for one named subwoofer. |
| Footprint | Sized to the driver diameter. 24.5 by 13.5 inches on the 10 inch. | Shared 30 by 15 inch platform on most builds. Down Fire Wide variants like this one run long and shallow for under seat fitment. | Compact per driver footprint. 21.5 by 14.5 inches on the 10 inch. |
| Front baffle | Single, 3/4 inch. | Double layer, outer layer machined as a flush recess. 1.5 inch. | Double, 1.5 inch. |
| Driver mounting | Solid flange. You drill your own mounting holes. | 8/32 threaded inserts, stainless machine screws included. | 8/32 threaded inserts, stainless machine screws included. |
| Joinery | V-groove and dado, CNC cut. | V-groove and dado, CNC cut, perimeter cross brace. | Stack fab, dowel reinforced. |
| Published alignment | Modeled Qtc profiles across a range of drivers. No single response curve. | A real predicted Qtc and F3 for that exact driver, calculated from its own Thiele-Small parameters. | Target alignment described in the listing. |
| Carpet | Gray standard, black optional. | Plush black. | Plush black. |
| Warranty | 1 year limited. | 1 year limited. | 2 years. |
Feet ship with every tier, uninstalled on purpose. Mount them where your floor wants them for a down fire install, or leave them off and run the cabinet front firing or up firing. The orientation is yours to choose.
This page is a Performance Optimized enclosure. The airspace, the cutout and the cabinet height all come from the driver's own numbers. A Performance box fits your subwoofer. A Performance Optimized box was built for it.
Built Around the Focal SUB 30 KXE
Nothing about this cabinet is generic. 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 airspace lands on 1.539 cubic feet net.
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, rated 800 watts RMS and 1600 watts maximum, with 22.5 mm of one-way excursion. It is 6.77 inches deep on a 12.52 inch frame, which matters on a down fire, where the motor rises into the cabinet. Every figure comes from Focal's own SUB 30 KXE technical sheet, including the published 4 liter displacement.
Net Volume and Alignment
The cabinet holds 1.539 cubic feet net, from 1.688 cubic feet gross after the brace and the driver's 0.14 cubic feet of displacement.
Height here is set by the driver's mounting depth, not by a volume target. The 6.77 inch motor needs 0.75 inch of clearance above it, so the cabinet can go no lower than 8.3125 inches. At that height the wide footprint holds 1.539 net, more than the 1.30 the standard 30 x 15 box was built to. More air lowers Qtc, which is the safe direction: a softer, better damped corner rather than a peakier one.
Computed from Focal's published Fs 29 Hz, Qts 0.46 and Vas 50 liters: Qtc 0.674, Fc 42.5 Hz, F3 44.7 Hz.
That lands just below maximally flat: a well-behaved sealed alignment with a slightly gentler corner than the standard box, which sits on Focal's Butterworth volume. Focal's own closed-box response chart is drawn at 25 and 35 liters; this cabinet, at about 44 liters, is larger than both.
True net, not marketing net. Internal volume is calculated from the machined cavity dimensions and the driver's displacement, not estimated from external dimensions minus wall thickness.
Down Fire Wide Construction
Cut with V-groove and dado joinery on our ShopSabre routers from Langboard Elite 3/4 inch MDF, a dense 48.5 lb/ft³ board with a 200 psi internal bond and 410,000 psi MOE. Every panel joint is a machined interlocking groove that mechanically locks before adhesive is applied, which keeps the cabinet airtight under sustained pressure cycling. Corners are square on Down Fire cabinets.
The cabinet measures 41 inches wide by 14 inches deep by 8.3125 inches tall, measured in the down fire position. Plan the space around the installed height rather than the cabinet height: the standoffs hold 1.75 inches under the baffle, so the finished stack sits near 10.0625 inches.
1.5 Inch Double Baffle
Two 3/4 inch layers laminated to 1.5 inches, with the outer layer machined as a flush recess so the driver bolts to the inner layer. Focal prints no bolt circle, so a threaded insert kit with stainless machine screws ships loose rather than pre-installed.
Windowed U-Brace
A windowed U-brace dadoed to the shell ties the long 41 inch panels together without taking a meaningful bite out of the airspace.
Side-Mounted Terminal Cup
Proline X ABS and carbon fiber composite cup with stainless hardware and copper ring terminals, pre-wired in 12 gauge OFC. Side mounted so it stays accessible with the baffle facing the floor.
Polyfill Installed
Polyfill is installed as a light wall lining to control internal reflections. It does not change the acoustic volume, so do not add more.
Motor Clearance and Orientation
The motor rises off the baffle into the cavity, so on a down fire cabinet the clearance that matters runs to the top panel. The 6.77 inch mounting depth leaves 0.793 inches above the motor in a 6.0625 inch internal height, against a 0.75 inch minimum. Height was set by that clearance, not by the airspace.
Focal does not publish a position on down firing this driver, and this cabinet makes no claim on their behalf. At the 1.75 inch standoff the floor slot is 0.79 times the cone area, under the 1.0 we aim for: the 12 inch cone is larger than the gap the feet leave under the baffle. Taller feet or a front-firing install both remove that, and the standoffs ship uninstalled so the choice is yours at install time.
Power, Mounting and Warranty
Focal rates the SUB 30 KXE at 800 watts RMS and 1600 watts maximum. The SUB 30 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 load against your amplifier's minimum stable impedance before powering the system.
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. The enclosure carries a 1 year limited warranty. Bring your own SUB 30 KXE; the driver is purchased separately.
Cut for the Driver, Not the Catalog
Down Fire Wide, 41 inches long and 14 deep, cut for one driver model and built one at a time in Tullahoma, Tennessee. Questions on fitment or amplifier matching, call us at 931-563-5151.
| Specification | Value |
|---|---|
| Series | Proline X Performance Optimized Down Fire Wide |
| Compatible Driver | Focal SUB 30 KXE (K2 Power), quantity 1. Direct fit |
| Enclosure Type | Sealed, down fire, floor coupled |
| Intended Fitment | Where height or depth is the limit and 41 in of length is available |
| Firing Direction | Down firing. Feet ship uninstalled, so front or up firing is also possible |
| External Width | 41 in |
| External Depth | 14 in |
| External Height | 8.3125 in, measured in down fire position, excludes standoffs |
| Installed Height | 10.0625 in including the 1.75 in standoff |
| Standard 30 x 15 Equivalent | 30 in W x 15 in D x 8.99 in H, 1.30 cu ft net |
| Internal Height | 6.0625 in |
| Internal Volume, Gross | 1.688 cu ft |
| Internal Volume, Net | 1.539 cu ft after the brace and displacement |
| Height Set By | Driver clearance: 0.793 in above the motor, the 0.75 in minimum plus rounding |
| Alignment | Qtc 0.674, Fc 42.5 Hz, F3 44.7 Hz, anechoic |
| Focal Closed-Box Chart | Drawn at 25 L and 35 L, Focal technical sheet |
| 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 |
| Voice Coil | 65 mm dual 4 ohm, CCAW on a glass fiber former, 4 layers |
| Floor Slot | 0.79 times the cone area at the 1.75 in standoff |
| Parameter Source | Focal SUB 30 KXE technical sheet, v1 29/09/2023 |
| Driver Power Handling | 800 W RMS / 1600 W maximum |
| Wiring Options | Dual 4 ohm coils: 2 ohm in parallel, 8 ohm in series |
| Mounting Depth | 6.77 in |
| Woofer Opening | 11.23 in |
| Driver Frame Diameter | 12.52 in, sits on the 14 in baffle |
| Driver Displacement | 0.14 cu ft |
| Material | Langboard Elite 3/4 in MDF |
| Joinery | V-groove and dado, CNC cut on ShopSabre routers |
| Panel Thickness | 0.75 in |
| Front Baffle | 1.5 in double baffle, outer layer machined as a flush recess |
| Internal Bracing | Windowed U-brace, dadoed to the shell |
| Corner Profile | Square, Down Fire series standard |
| Driver Mounting | Threaded insert kit included, NOT pre-installed: Focal prints no bolt circle |
| Terminal Cup | One Proline X ABS and carbon fiber composite, side mounted, pre-wired 12 gauge OFC |
| Damping | Polyfill installed as a light wall lining, does not alter acoustic volume |
| Standoffs | Included, 1.75 in, shipped uninstalled |
| Carpet | Plush black |
| Bundle Options | Enclosure only, bring your own SUB 30 KXE |
| Warranty | 1 year limited |
| Built In | Tullahoma, Tennessee |
01Is it a sealed driver?
Efficiency bandwidth product places the motor before anything else is decided.
02What the box does to it
1.539 cu ft against a 50.0 L Vas.
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.
| 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.
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.
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 |
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.
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.
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.
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.
Handcrafted in USA
Hand-assembled at our facility in Tullahoma, TN. Every enclosure is inspected before it ships.
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.
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