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.
Imaging
Before 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.