Performance Optimized Down Fire Sealed 12" Enclosure DD Audio SL712 · Single 12" Sealed enclosure

Both SL712 coils, yes. The D2 and D4 share one basket, one 11.375 inch cutout, one 12.375 inch frame and one 5.5 inch mounting depth, and DD Audio publishes one Thiele-Small block for both, so the fit and the alignment are the same whichever coil you own.

Any other 12, no. The baffle is cut direct fit for the SL712 and the airspace is built to that driver's published parameters. Another woofer that happened to drop into the hole would be loading into an airspace engineered around a 0.54 Qts and a 39.2 liter Vas, and the alignment printed on this page would no longer describe what you own.

DD Audio publishes a 0.7 to 1.5 cubic foot sealed range for the SL712, and 1.00 cubic feet sits inside it. At that volume the system Qtc is 0.83 with resonance at 44.8 Hz and an anechoic half-power point of 39.0 Hz, a punchy sealed alignment with a mild lift near resonance.

The reason not to go bigger is what the extra volume buys. At DD's 1.5 cubic foot ceiling the Qtc falls to 0.75 but F3 only moves to 38.1 Hz, less than a hertz, while the cabinet grows almost three inches taller. On this driver volume buys damping, not extension, so 1.00 keeps the cabinet at 7.27 inches without giving up low-frequency reach.

The SL712 is rated 1000 watts RMS, so target 700 to 1000 watts RMS at the final wired impedance. The D2 coil gives 4 ohms in series or 1 ohm in parallel; the D4 gives 8 ohms in series or 2 ohms in parallel.

The 1 ohm parallel load on a D2 is the one to be careful with. Many amplifiers are not stable at 1 ohm and running one there is how amplifiers die. Series for 4 ohms is the safe answer on a D2 unless your amplifier is explicitly rated 1 ohm stable. On a D4, parallel for 2 ohms is the usual choice.

The cabinet is 7.27 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 9.02 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 7.27 is what holds exactly 1.00 cubic feet net around the SL712.

The baffle is two bonded 3/4 inch sheets, 1.5 inches through. A subwoofer pushes as hard against its mounting surface as it does against the air, 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 so the driver bolts to the inner layer, which recovers 3/4 inch of internal clearance. That matters here: the SL712's 5.5 inch motor sits 4.0 inches into a 5.02 inch cavity, and the recess is part of what keeps 1.02 inches of air above it.

Anechoic F3 is 39.0 Hz at 1.00 cubic feet, with system resonance at 44.8 Hz. Because the Qtc is 0.83 the response carries a mild lift around resonance rather than a flat shelf, so F3 lands below fc.

Those figures are anechoic and exclude cabin gain. In a car the transfer function of the cabin adds real output below 50 Hz, so in-vehicle response runs deeper than the number 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 1.00 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 standoffs, the polyfill lining already in place, and a threaded insert kit with stainless machine screws.

The inserts ship loose rather than pressed into the baffle, because DD Audio publishes no bolt pattern for the SL712. Set the basket in the recess, mark its holes, and press the inserts to your driver. The SL712 itself is purchased separately.