Performance Optimized Down Fire Sealed 12" Enclosure Focal SUB 30 KXE · Single 12" Sealed enclosure

The SUB 30 KXE, yes. 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 6.77 inch motor clears the cabinet with 1.46 inch to spare, and the KXE ships in one version, dual 4 ohm, so there is no coil variant to choose.

Any other 12, no. The airspace is engineered around the KXE's 0.46 Qts and 50 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 29 Hz, Qts 0.46 and Vas 50 liters: system Qtc 0.707, maximally flat, with resonance and half power both at 44.6 Hz. Focal's own closed-box response chart for this driver is drawn at 25 and 35 liters, and this volume sits at the larger of the two.

One caveat on Focal's sheet: its moving mass and resonance imply a Vas nearer 58 liters than the printed 50. If that is the truer figure, this cabinet reads Qtc 0.74 instead, a touch livelier. Either way it is a well-behaved sealed alignment.

Focal rates the SUB 30 KXE at 800 watts RMS and 1600 watts maximum, so target 560 to 800 watts RMS at the final load.

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 your amplifier's minimum stable impedance first.

The cabinet is 8.99 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 10.74 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.

The baffle is two bonded 3/4 inch sheets, 1.5 inches through. The KXE moves 1130 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 12.52 inch frame, so the driver bolts to the inner layer.

Anechoic F3 is 44.6 Hz with system resonance at 44.6 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 1.30 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 30 KXE, so you set the driver in the recess, mark its holes, drill and press the inserts. The Focal SUB 30 KXE is purchased separately, and the cabinet is cut direct fit to it, not a general purpose 12 inch box.