Dayton Audio Ultimax II UMII12 Box: Ported 12" Down Fire Enclosure Single 12" Ported enclosure

The port runs 19.4 m/s in the channel and 14.8 at the mouth at the 800 W design power, and the cone peaks at 8.5 of its 22 mm. Passband ripple is 1.8 dB and the in-car spread from 25 to 60 Hz 1.1 dB. Tuning is chosen for in-car response rather than for an anechoic curve: a vehicle adds roughly 12 dB per octave below about 45 Hz, so a box tuned very low reinforces a region the cabin is already reinforcing and leaves 40 to 60 Hz thin. In this cabinet that lands at 1.1 dB of in-car spread across 25 to 60 Hz, which is where kick and bass fundamentals live.

No, and on this build in particular do not add any. Every sealed Proline X enclosure ships with polyfill pre-installed; a ported one must not, because damping material changes the effective volume the port is tuned against. The port on this cabinet is cut to 28.60 inches of centreline path for 32.5 Hz. Stuff it and you move the tuning without shortening the port, which gives you a mistuned box rather than a bigger-sounding one. The 1.75 dB passband you are paying for depends on it staying dry.

Yes, at 26 Hz, 24 dB per octave. Below tuning a vented box stops loading the cone and excursion runs away toward DC. With the filter in place this cabinet puts the Dayton Audio Ultimax II UMII12 at 39 percent of its usable travel at full rated power; without it there is no meaningful number to quote, because the excursion curve does not converge. On a sealed build a subsonic filter is an improvement. Here it is required equipment.

Dayton Audio rate the Ultimax II UMII12 at 800 W RMS and that is the thermal ceiling. The figures on the Performance Graphs tab are a different quantity: they are mechanical limits, the power at which the cone reaches the end of its linear travel in this specific cabinet. Here the cone sits at 39 percent of usable travel at the driver's own rating, so heat is what stops you, not travel. Final wired impedance and amplifier output are separate questions again.

Not one we can show you. We do not build a sealed enclosure for the Dayton Audio Ultimax II UMII12 and Dayton Audio publish no sealed volume for it, so the Performance Graphs tab carries no ported-versus-sealed chart: the only sealed box left to plot would be this cabinet stuffed and sealed, which nobody would build, and a comparison against it would tell you nothing you could buy. What a vented box gives up is the region below tuning, where the cone unloads and the 26 Hz subsonic filter takes over; around 32.5 Hz the vent carries the load and cone travel drops to its minimum, which no sealed alignment can do.

It is a slot port formed by one folded wall: a leg down the long side of the cabinet past the woofer ring, one faceted 90 degree bend, and a leg across the end opening through a chamfered corner. On this cabinet that is 28.60 inches of centreline path and 20.3 square inches of channel, exiting a 26.5 square inch mouth. Air leaves at 14.8 metres per second at tuning against a 17.0 threshold, and the channel runs at 54 percent of its turbulence limit. One wall and one bend rather than a serpentine's three means less wall area inside the box, fewer joints to leak, and one place for flow to separate instead of three.

V-groove and dado joinery in 0.75 inch Langboard Elite MDF with a double-layer 1.5 inch baffle. The driver mounts to a 13.625 inch ring bonded under the baffle in a machined recess, carrying eight #8-32 hurricane nuts so it threads into steel rather than MDF. A windowed brace sits 2.82 inches clear of the cutout edge and 1.65 inches clear of the port terminus; the window is not weight saving, a solid panel there would split the cavity and make the box a bandpass. Walls seat into dados in both the lid and the baffle. Square corners, plush black carpet, side-mounted terminal cup.

No. This is an enclosure only, cut and folded for the Dayton Audio Ultimax II UMII12 specifically. The 11.272 inch cutout, the 7.059 inch mounting depth allowance and the 1.43 cubic foot alignment all come from Dayton Audio's published parameters for this exact driver, and the port is sized against its Xmax and power rating. It is not a universal box with a 12 inch hole in it. Bring your own driver.