Performance Optimized Down Fire Sealed Dual 12" Enclosure Focal SUB 30 KXE · Dual 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 4.21 inch to spare, and the KXE ships in one version, dual 4 ohm, so there is no coil variant to choose. Run two so the chambers match.

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.

Height. At Focal's published Fs 29 Hz, Qts 0.46 and Vas 50 liters the Butterworth box is 1.30 cubic feet per driver, and two of those on the 30 by 15 platform make a cabinet 16 inches tall. At 0.85 per chamber it stands 11.73 inches, in line with the taller dual 12 down fire boxes in the range.

The alignment is Qtc 0.807, resonance 50.9 Hz, half power 45.3 Hz: firmer than maximally flat, with a mild rise ahead of the rolloff and about 0.8 Hz less extension than the Butterworth box. Focal's own closed-box response chart is drawn at 25 and 35 liters; at about 24 liters per chamber this cabinet sits on the smaller 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 0.85 instead, a touch livelier.

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

Each SUB 30 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 your amplifier's minimum stable impedance first.

The cabinet is 11.73 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 13.48 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.

Two drivers sharing one sealed volume load each other: each driver's compression stroke becomes the pressure the other works against, which blurs the alignment either would have alone. A bonded full-height 3/4 inch divider gives each driver its own 0.85 cubic feet and its own polyfill.

It also means a failure in one driver does not unload the other, and the alignment on this page is the alignment in each chamber, not an average across a shared box.

Anechoic F3 is 45.3 Hz per chamber with system resonance at 50.9 Hz. Above Qtc 0.707 the response rises slightly ahead of the rolloff, so F3 sits below fc.

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 in both chambers 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 0.85 cubic feet per chamber 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 to both positions, 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 pair of Focal SUB 30 KXE is purchased separately, and the cabinet is cut direct fit to it, not a general purpose 12 inch box.