Performance Optimized Down Fire Wide Sealed Dual 10" Enclosure | Focal SUB 25 KXE

The Down Fire Wide Format

Down Fire Wide is the Performance Optimized answer to a specific problem: the space under the rear seat of a truck or SUV, or a narrow cargo floor, is long and shallow, and the standard 30 by 15 inch Down Fire cabinet will not go in it.

This cabinet takes the same pair of Focal SUB 25 KXE and turns the footprint sideways. It runs 41 inches wide by 12 inches deep by 10.5 inches tall: 3 inches shallower front to back than the standard 30 x 15 cabinet and 11 inches longer. The airspace given up in depth is recovered along the length, and each driver still gets its own separate chamber.

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.

Built Around a Pair of Focal SUB 25 KXE

The baffle is cut to 9.30 in (236 mm) at both positions. 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 10.55 inch (268 mm) frame still covers it with margin. That frame sits on the 12 inch deep baffle.

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, rated 600 watts RMS and 1200 watts maximum, with 22.5 mm of one-way excursion. It is 6.77 inches deep, which matters on a down fire, where the motor rises into the cabinet.

Every figure comes from Focal's own SUB 25 KXE technical sheet. One number on it is soft: Focal prints 20 liters of Vas, but the published moving mass and resonance imply nearer 16 liters. If that is the truer figure, the Qtc on this page reads a few hundredths lower, so treat it as a range a few hundredths wide.

Focal does not publish a position on down firing this driver, and this cabinet makes no claim on their behalf. The standoffs ship uninstalled, so front or up firing remains your choice at install time.

Net Volume and Alignment

Each chamber holds 0.836 cubic feet net, 1.672 cubic feet across both chambers, from 0.965 gross per chamber after the driver's 0.11 cubic feet of displacement.

Computed from Focal's published Fs 38 Hz, Qts 0.52 and Vas 20 liters, that produces Qtc 0.706 with Fc at 51.6 Hz and a predicted F3 of 51.7 Hz per chamber.

Height is the free dimension. With the footprint fixed at 41 by 12, the cabinet height was solved to put each chamber on the 0.83 cubic feet the standard 30 x 15 cabinet was built to, then rounded up to the next sixteenth so the airspace lands on the target rather than under it. The 6.77 inch mounting depth leaves 2.98 inches above the motor, so airspace set the height here, not clearance.

That is effectively the Butterworth alignment: maximally flat, with system resonance and half power almost coincident. Focal's own closed-box simulations for this driver run at 16 and 30 liters, and this volume sits between them.

These are anechoic figures. Firing down into the floor, the sealed rolloff meets rising cabin gain, so in-car response extends below them.

Two Chambers, Not One

This enclosure follows the Proline X standing design rule for dual sealed builds: two fully separate chambers divided by a bonded full-height 3/4 inch MDF panel.

Two drivers sharing one sealed volume interact acoustically. Each driver's compression phase becomes the pressure environment the other is working against, which smears transient response and blurs the alignment each would have on its own. A full divider eliminates that. Each driver gets its own 0.836 cubic feet and its own polyfill.

On a long cabinet the divider does structural work as well, tying the front and rear walls together at the center of a 41 inch span.

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 both chambers airtight under sustained pressure cycling. Corners are square on Down Fire cabinets, no radii. Polyfill is installed as a light wall lining, finished in plush black carpet.

The cabinet measures 41 inches wide by 12 inches deep by 10.5 inches tall, measured in the down fire position, excluding standoffs. The 1.75 inch standoffs ship with the enclosure but are not installed. Fitted, the installed height is 12.25 inches, so plan the space around that stack.

Power and Wiring

Focal rates the SUB 25 KXE at 600 watts RMS and 1200 watts maximum, 1200 watts RMS combined. Target 420 to 600 watts RMS per driver at the final load.

Each SUB 25 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. One side mounted cup feeds both positions.

Focal's drawing shows eight mounting holes but prints no bolt circle, so the baffle ships undrilled with a threaded insert kit: set the driver in the recess, mark its holes, drill, press the inserts and bolt it down.

Bring your own pair of SUB 25 KXE; the drivers are purchased separately. The enclosure carries a 1 year limited warranty. Questions on fitment or amplifier matching, call 931-563-5151.