Subwoofer Enclosure - Tricks Of The Trade

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.

Speaker Pods - Door Pod Express

Creating a quality audio system requires more than just good speakers. In order to create a well-balanced soundstage, the speakers need proper placement-not always an easy task when dealing with the tight spaces of modern cars. Many times we have to relegate ourselves to modifying the factory placements for better imaging. One way to do this is building new door panels, which is a pretty complicated endeavor. There are, however, more simple methods of achieving this goal.
Depending on the vehicle, there are options using factory panels or grilles. For our Nissan 350Z, we used the factory door speaker grilles as a base for our pods. By modifying the factory panels, we can change the directional imaging of the speakers, creating a well-balanced soundstage.
ImagingBefore any actual mods can begin, the speakers should be imaged. This is a lengthy process that involves listening tests and aiming the speakers, but with a couple of shortcuts, the results can be pretty amazing. One of the best tricks for quick imaging is to aim the driver's-side midrange at the passenger's left ear and the passenger's-side speaker, at the driver's right ear. This will create a cross point in the center of the vehicle, equalizing the path lengths as much as possible without relocating the speakers. If you're using components, try aiming the tweeter at the rearview mirror or a centered point 3-4' in front of the passenger's head. This creates a separation that allows both waves to hit the listener's ears at nearly the same time. These tricks don't work perfectly all the time and probably won't win any SQ competitions but, for a daily driver, they offer better imaging without hours of testing.
The build process is pretty simple and requires very little tools. If you have access to an air compressor, a DA sander and a die-grinder, they'll be your best friend, and allow you to save time when shaping and sanding parts. If not, you can always do it the old-fashioned way and sand by hand. If you must hand sand, don't wait until the body filler is fully cured. Instead, let it go green-the stage in which the filler is just beyond rubber. If you start your rough shaping now, the filler will roll-off quickly and easily, letting you get the shape you want faster and with less fatigue. The entire process is detailed here with Jason Carson of Red Dirt Rodz doing the dirty work. Just remember, a little patience goes a long way in this business-rushing the job will only make it take longer.
We started the project with a pair of 31/44" MDF rings that we cut to match the outside diameter of the Kicker speaker grilles. Once we decided the best angle for the speakers, we used a die-grinder to sand and angle the topside of the ring. This can be done with a belt sander as well.
We placed the rings on the door panels and rotated them until we had the placement we wanted. The rings need to be smaller than the door grille. Ours are roughly 0.5" smaller overall.
We scuffed the door grilles (for better adhesion) and glued the rings to the grilles.

Fiberglass Quarter-Panel Fabrication - JS Designs/Sony Civic Si 3 4

Fiberglass Quarter-Panel FabricationThis month we'll look at the construction of the fiberglass trim panels for the rear quarter-panel area (sides of the back seat). In my early planning stages, one of my goals for the JS Designs Honda Civic Si was to have an extremely loud and fun system. Basically, while driving the car I wanted it to sound like a concert or a dance club. To accomplish this, I integrated six sets of Sony XS-D170SI speakers into the car as a whole, with two component sets for each third of the vehicle.
For example, my design called for two component sets in the front doors, two in the back seat panels and two in the rear hatch. This division of the component sets created a balance of sound in the car from front to back; I had already created the ported subwoofer enclosure for three 12" subs. Five 8" speakers equaled the active radiating area (or SD ROM) of the three 12" drivers, the Sony drivers are 6.75" so 12 of these drivers are more than capable of keeping up with the high excursion of the Sony subwoofers.
Two of the six sets were placed into newly fabricated rear trim panels for the back seat. These panels sit adjacent to the large, fiberglass amprack that holds the six Sony amplifiers and 12 Sony LCD monitors. I wanted the panels to fit in the same way that the factory panels fit plus I wanted them to serve as a trim panel over the enclosure for the 6.5" component set. The panels were designed in a way so that the overall shape flowed with the factory lines of the car and, in the end, enabled all of the back seat panels to flow together as one shape.
Next month, we'll take a break from the Civic Si construction and examine how to do some clean, structured wiring. In the meantime, if you would like any additional pictures or information, please feel free to contact me at info@jasonsyner.com.
Using the side of the amprack as a template, a piece of MDF was cut and flush-routed to match its shape. This piece will later become the outer framework for the side panel, which will also be used to transition the side panel into those I built for the backseat area. When I used a router/lift combo (available from www.mobilesolutions-usa.com) speaker openings were cut into the panel and flush-routed. To trim in the speaker grilles, 11/42" MDF rings were cut. Eighth-inch stainless steel brackets bolt the MDF to the supporting metal in the quarter-panels of the vehicle. This picture shows the MDF panel bolted into place inside the vehicle. This picture shows the speakers test-fitted into the enclosure.