With the door speakers installed, it’s time to move on to the trunk. The enclosure for the Hertz subwoofer will take shape in the left side trim panel of the trunk. To prevent accidental damage to the vehicle, the trim panel is removed from the car, and temporary stilts are made to keep it’s shape on the table. The entire surface of the panel is covered in 3M high quality masking tape, and a few coats of mold release wax are applied. A Sharpie line marks the outside boundaries of the area we want to capture. Fiberglass mat and resin are applied, over and over. For the subwoofer and the power it will receive, we need to build up a layer at least 3/16″ all over. Before taping the panel, we temporarily added 1.5″ to the floor of the panel and then taped over it. When the enclosure is removed, it will hover 1.5″ above the floor of the car so that the factory trunk mats can be reinstalled without modifications. When building enclosures like this, we also add a black pigment to the fiberglass resin so that if it ever needs service in the future, the enclosure will have a clean, uniform appearance. With the back half of the enclosure removed, the front is built from 3/4″ MDF and attached. The seam between the wood and fiberglass form is sealed and reinforced with our own custom mix of chemicals we call “The concoction.” The trim panel is back in the car, and the enclosure is temporarily held in place with the telescoping rod. With fiberglass molds, there is always some shrinkage. We pack filler into the small gaps between the trim panel and enclosure for a perfect fit.
The enclosure is wrapped in matching carpet and bolted in place. We machined this grille from wood, plastic, aluminum and steel. The colors and design mimic the factory tweeter locations on the front pillars of the Jetta. A thin 1/8″ ring of polished aluminum around the grille shape really makes it unique. The grille is securely attached with a set of hidden plastic snaps, and is also easily serviced by prying off the entire grille cover. The red glow comes from the new trunk lighting. The original light was replaced with a pair of very bright red LED bulbs. The power for the system comes from this Arc KS300.4 amplifier. Arc amplifiers are the choice of many professionals who compete in the sound quality arena. Next to the amp are the passive crossovers for the Hertz Mille components in the front doors. Everything is attached to a fully welded steel rack we built, which will bolt into the top of the trunk for easy service. In this picture, all of the components are prewired, leaving just a clean pig tail of wires that come out the side and quickly disappear behind the carpet on the side of the trunk.