Performance Optimized Down Fire Sealed 10" Enclosure Focal SUB 25 KXE · Single 10" Sealed enclosure

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.

Because the KXE's 6.77 inch mounting depth sets the minimum cabinet height on the 30 by 15 platform, not the target volume. The motor reaches 5.27 inches into the cavity and needs 0.75 inch above it, which puts the cabinet at 8.27 inches tall and the airspace at 1.18 cubic feet whether the alignment wants it or not.

The result is a slightly over-damped alignment, Qtc 0.658, resonance 48.1 Hz, half power 51.9 Hz: a gentle rolloff rather than a flat one. The wedge and the dual down fire, where the motor does not bind, hold the 0.83 Butterworth volume.

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.

The cabinet is 8.27 inches tall measured in the down fire position, and that figure excludes the standoffs. The standoffs hold 1.75 inches under the baffle, so plan your space around a finished stack of roughly 10.02 inches.

The footprint is the standard Performance Optimized down fire platform, 30.00 inches wide by 15.00 deep. Height is the only dimension solved to the driver, and here it is the KXE's 6.77 inch motor that sets it.

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.

Anechoic F3 is 51.9 Hz with system resonance at 48.1 Hz. Below Qtc 0.707 the rolloff is gentle and F3 sits above fc, which is what an over-damped sealed box does.

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.

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 1.18 cubic feet this cabinet was built to.

No driver. This is an enclosure only. You receive the cabinet finished in plush black carpet, one side-mounted pre-wired terminal cup, the polyfill lining already in place, the standoffs, 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.