The increase in voice coil size also required changes in the metal components of the motor structure. The most notable is the redesign of the Compound Radius Curve (CRC) pole piece. The pole piece is the magnetic return in the center of the VC that usually, and in the case of the SWX-1243D, contains the vent hole you see at the rear of the driver. At the top of the pole, the newly designed CRC helps smooth the air flow and focus it through the copper shorting ring and heatsink. More importantly, the shape of the CRC controls the flux fringe field-the dispersion of magnetic flux within the magnetic field. By changing its design, Alpine was able to extend the range of the magnetic flux, thus bettering the magnetic x-max over that of the mechanical x-max. This means that the VC will always stay within the magnetic gap, thereby lowering distortion at high-power levels. It also increases the efficiency of the motor, and with efficiency comes better response and more output.
These improvements should go a long way in the performance of this driver, so let's get to the good stuff.
Getting Ready
A bifold, single-sheet owner's manual contains information on both the 10" and 12" versions of the Type-X subwoofers. Information is provided in English and French, covering features, specifications, enclosure information, electro-mechanical parameters. There are also detailed illustrations that tell driver dimensions and application diagrams, which help users determine how to achieve the proper impedance for their system by using the VC configuration jumpers for the dual 4-ohm driver. Registration and warranty cards are also included, specifying the coverage and one-year warranty.
Normally, I prefer to test subwoofers in the recommended enclosures listed in the owner's manual, but Neill of Alpine was up front saying that the best performance would be achieved in a larger-than-recommended sealed enclosure netting 1.5ft3 (the manual recommends 0.65-1.25ft3). Per this recommendation, I built an enclosure out of 3/4" MDF with a 1.5" faceplate and minimal polyfill inside. I inserted the thoughtful VC configuration jumpers in the proper slots to achieve a 2-ohm load and connected the 12-gauge speaker wire to the gold-plated brass block terminals (insulated by an injection-molded form) using the provided hex wrench to secure the set screw. The C-shaped rubber gasket stretched over the basket's mounting flange provides a tight seal against the enclosure. Once screwed in place, a slick cosmetic rubber cover press fits on top of the gasket, hiding the screws altogether.
The enclosure was placed in the rear cabin of my F150 and adjusted to the optimum position. For this test, I installed a 2,200-watt Zapco C2K 9.0. After a little adjustment, the crossover was set to 70Hz at 12dB to achieve the best transition with my system's midbass.