This month we'll finish up the subwoofer enclosure in our '07 Project Toyota Avalon. This enclosure demonstrates how a large subwoofer can be integrated cleanly into a trunk while maintaining trunk space. It's also a perfect spot to put a subwoofer, since it loads correctly with the vehicle's interior and avoids cancellation. This is by far one of my favorite enclosure building techniques and I've used it in many vehicles with success. If you're looking to take back some of your trunk or hatch space, do yourself a favor and spend a weekend or two integrating your subwoofer into your vehicle-you won't regret it. Send questions to techpanel@sourceinterlink.com with Tricks of the Trade in the subject line, and check out stevebrownuniversity.com.
Since we finished the back or base of the enclosure last month, we bolted it in the car to check the fit. Next, attach the ring that holds the speaker to the enclosure base. CA glue, or super glue, works great to temporarily tack the ring in place while the fit is checked. Be sure to allow enough depth for the subwoofer to mount properly without hitting the back of the enclosure. Using Duraglas, bond each of the braces to the enclosure.
After trimming off the excess carpet, your enclosure should look like this. Notice the green masking tape applied to all exposed edges, necessary to keep fiberglass resin out of these areas. This little trick will save tons of time later, since you won't have to grind the excess resin out from where you don't want it. Make a ring from two layers of 31/44" MDF to mount the subwoofer. Notice that the bottom ring is smaller than the top one in order to mount the subwoofer and also make it flush with the surface of the box when complete. Route a notch, or rabbet, into the outside edge to make it easy to staple on our surfacing material later.
If you plan on bolting an amplifier to the enclosure, add a 31/44" MDF plate ahead of the subwoofer ring as a place to mount it. Note the rabbeted notch added to this panel. With the frame structure complete, it's time to add our shaping material to the front of the enclosure. This makes the box very strong, seals it up and creates the final shape of the front side. Non-backed stretchy carpet works great for this, since it's thick and durable when soaked with resin. Pull the carpet tight over the box surface and attach the carpet to the edges of the fiberglass base using CA glue.