MTX 5512-22 Box: Sealed 12" Wedge Enclosure Single 12" Sealed enclosure

The 5512-22, yes. The baffle is cut to 11.188 in for MTX's 12.375 in frame. The 6.25 inch motor clears the raked rear panel with 0.75 inch to spare.

Any other 12, no. The airspace is engineered around the 5512-22's own Qts of 0.69 and Vas of 44.46 litres, and a different woofer that happened to drop into the hole would not see the alignment printed on this page.

1.25 cubic feet net on MTX's published figures: the 5512-22 reads Qtc 1.036 with resonance at 51.1 Hz and half power at 39.5 Hz. That is MTX's own recommended sealed volume for this driver.

This driver's Qts is 0.69. System Q can only rise as the box shrinks, so no sealed enclosure of any size puts this woofer at the 0.707 maximally flat alignment, and a box large enough to approach it would not fit a trunk. Built to MTX's own recommended airspace it lands at Qtc 1.036, which is well above maximally flat: an obvious lift near resonance, a warm and heavy midbass, and a shorter reach than a lower-Q alignment. If you want the extra depth rather than the sealed box's smaller cabinet and gentler power demands, we build a ported wedge for this same driver that reaches 33.4 Hz.

MTX rates the 5512-22 at 400 watts RMS, so target 280 to 400 watts RMS at the final load.

MTX sells this model as the dual 2 ohm version: two 2 ohm coils, 4 ohms in series or 1 ohm in parallel. A parallel load at or under 1 ohm needs an amplifier rated for it. Confirm your amplifier's minimum stable impedance first.

The seat-side face carries a 20 degree rake that matches the lean of a factory rear seat back, so the cabinet sits flush against it and the cargo space in front stays usable. The baffle is the vertical trunk-lid-side face, so the driver fires rearward into the trunk cavity.

The trunk acts as an acoustic extension for the sealed box, and the cabin adds real output below 50 Hz, so in-vehicle response runs deeper than the anechoic 39.5 Hz on this page.

The baffle is two bonded 3/4 inch sheets, 1.5 inches through. A single 3/4 inch panel flexes under the pressure a 12 inch woofer puts on it at 400 watts, which smears output and works the driver loose over time; the second layer stiffens the face and gives the mounting hardware twice the material to bite.

The outer layer is machined as a flush recess to MTX's 12.375 inch frame, so the driver bolts to the inner layer and sits flush with the gloss black acrylic insert.

Anechoic F3 is 39.5 Hz, with system resonance at 51.1 Hz. At Qtc 1.036 the response carries a lift near resonance and F3 sits below fc, so the box reads full and punchy rather than extended. Our ported wedge for this same driver reaches 33.4 Hz if you want the extra depth.

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 1.25 cubic feet this cabinet was built to.

No driver. This is an enclosure only. You receive the cabinet finished in plush black carpet with the gloss black acrylic baffle insert, one side-mounted pre-wired terminal cup, the polyfill lining already in place, and a threaded insert kit with stainless machine screws.

The inserts are not pre-installed: MTX publishes no bolt circle for the 5512-22, so set the driver in its recess, mark its holes, drill and press the inserts. The MTX 5512-22 is purchased separately, and the cabinet is cut direct fit to it, not a general purpose 12 inch box.