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

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

Nothing about this cabinet is generic. 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 airspace lands on 0.83 cubic feet net per chamber, the Butterworth volume on Focal's figures.

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 on a 10.55 inch frame, 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 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.

Two Chambers, Not One Volume

This enclosure follows the Proline X standing rule for dual sealed builds: two fully separate chambers split by a bonded full height 3/4 inch MDF divider, each driver in its own 0.83 cubic feet with its own polyfill.

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 either would have on its own. A full divider removes that entirely. One shared side mounted terminal cup feeds both driver positions, so the cabinet stays a single connection point.

Net Volume, Not Gross

Each chamber is built at 0.83 cubic feet net per driver, out of 1.93 gross after the divider and Focal's published 3 liter driver displacement. At 0.83 cubic feet the KXE lands at Qtc 0.707, maximally flat, with system resonance and half power both at 51.7 Hz. Focal's own closed-box simulations run at 16 and 30 liters, and this volume sits between them.

Down Fire Construction

Cut with V-groove and dado joinery on our ShopSabre routers from Langboard Elite 3/4 inch MDF. 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 30.00 inches wide by 15.00 inches deep by 11.23 inches tall, measured in the down fire position and excluding standoffs. 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 12.98 inches.

Motor Clearance and Orientation

The motors rise 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 puts the motor 5.27 inches into a 8.98 inch cavity, leaving 3.71 inches above the motor against a 0.75 inch minimum. Height was set by the airspace, above the minimum the clearance alone would have required.

Focal does not publish a position on down firing this driver, and this cabinet makes no claim on their behalf. The feet ship uninstalled, so if you would rather run it front firing or up firing, that is a decision you can make at install time without changing anything about the enclosure.

Power, Mounting and Warranty

Focal rates the SUB 25 KXE at 600 watts RMS and 1200 watts maximum, 1200 watts RMS combined. 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. 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 pair of SUB 25 KXE; the drivers are purchased separately.