Dayton Audio Ultimax II UMII18 Box: Ported 18" Wedge Enclosure Single 18" Ported enclosure

The port runs 18.2 m/s in the channel and 12.3 at the mouth at the 1200 W design power, and the cone peaks at 8.2 of its 28 mm. Passband ripple is 2.9 dB and the in-car spread from 25 to 60 Hz 3.4 dB. Tuning is chosen for in-car response rather than an anechoic curve: a vehicle adds roughly 12 dB per octave below about 45 Hz. In this cabinet that lands at 3.4 dB of in-car spread across 25 to 60 Hz.

The raked face is the seat side. A factory rear seat back leans about 20 degrees off vertical, so the cabinet sits flat against it and uses floor a square box wastes. The baffle stays vertical and fires rearward into the trunk, which acts as the acoustic extension into the cabin. This one is 17.77 inches deep at the base and 10.12 at the top, 30.00 wide and 21 tall.

Yes, at 23 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 UMII18 at 29 percent of its usable travel at full rated power; without it there is no meaningful number to quote.

Dayton Audio rate the Ultimax II UMII18 at 1200 W RMS and that is the thermal ceiling. The Performance Graphs tab shows the mechanical limit, the power at which the cone reaches the end of its travel in this cabinet: here the cone sits at 29 percent of usable travel at the rating, so heat is what stops you, not travel. A D2 coil is 4 ohms in series or 1 ohm in parallel; run series unless the amplifier is rated for 1 ohm. A D4 is 8 series or 2 parallel.

Not one we can show you. We do not build a sealed enclosure for the Dayton Audio Ultimax II UMII18 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 23 Hz subsonic filter takes over; around 29.5 Hz the vent carries the load and cone travel drops to its minimum, which no sealed alignment can do.

It is a triangular slot in the bottom-rear corner: the floor and the raked back wall are two sides, one bevelled panel is the third. It runs across the cabinet, opens into the box through a 4.51 inch gap at the far end and exits through the side panel as the same triangle. Straight, no bend: 23.74 inches of path and 28.2 square inches of channel running at 18.2 metres per second, 53 percent of its turbulence limit. The three mouth edges are rounded over at 1/2 inch, so the opening at the face is 41.7 square inches and the air leaves it at 12.3 metres per second against the 17.0 threshold where a slot port starts to chuff; the panel's throat end is rounded at 3/8 inch for the same reason. The terminal cup is on the other side.

No, and do not add any. Every sealed Proline X enclosure ships with polyfill; a ported one must not, because damping changes the effective volume the port is tuned against. The port here is cut to 23.74 inches for 29.5 Hz. Stuff it and you move the tuning without shortening the port.

No. This is an enclosure only, cut for the Dayton Audio Ultimax II UMII18 specifically: the 16.839 inch cutout, the 8.996 inch mounting depth allowance and the 2.72 cubic foot alignment all come from Dayton Audio's published parameters. Dayton make the UMII18 in one version, dual 2 ohm (UMII18-22). Bring your own driver.