The soul of this long-excursion subwoofer is the MMAG motor structure. Since the voice coil in the UL12 is shorter than the combined length of the two gaps (46mm gap total including spacer height), it appears to be similar to a conventional underhung voice coil motor, but the Critical Mass motor functions in a very different manner. It operates in such a way that the two gaps are always working in conjunction with each other and the total number of wire turns does not begin decreasing until the voice coil starts to leave just one gap.
The cone assembly for the Critical Mass subwoofer is no less technically impressive than the frame and motor structure. Built from layered and laminated carbon graphite and glass fiber, the cone is further reinforced by both the large 6" diameter concave dust cap (made from the same composite material as the cone) and by having the outside perimeter of the cone turned down 90 degrees. This down-turned edge contributes a tremendous amount of rigidity to the rim of the cone assembly. Add to this the circular "flying buttress" support that joins the cone to the voice coil former and the entire assembly moves like one solid mass.
Long excursion in a subwoofer requires the suspension to move long distances. The solution used by Critical Mass for the UL12 is a patent-pending technology that vertically glues the outside edge of the surround to the frame, allowing the surround to be attached closer to the outside perimeter of the frame, and this equates to more cone area, or Sd (Sd is an engineering abbreviation for the area of a cone). Rather than being low and wide, the thermally formed foam/rubber surround is a modified ellipsoid shape and is more tall and narrow that the previous generation of wide surrounds. The result is the same excursion ability, but a greater cone diameter and area.
The rest of the cone assembly consists of a single 7"-diameter poly fiber resin composite spider that has been optimized to a progressive-regressive hybrid geometry (the wiggles are taller and more narrow at the outside edge of the spider). Tinsel lead wires from the voice coil are stitched in two places to the spider surface. The dual four-layer voice coil is wound with round aluminum wire with an ultra high-temperature insulation on a black anodized 76.6mm (3") diameter aluminum former with a collar made of multiple reinforcing layers of non-thermally conduction materials (spun lace Nomex and Polyimid). Voice coil tinsel leads are connected to dual color-coded gold-plated push terminals located on opposite sides of the frame.