Performance Optimized Wedge 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.

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.

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 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.

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.

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.

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.

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.