This month we'll finish up installing the 10" Alpine subwoofer in our Volvo S60 sedan. The first thing on the agenda is to stretch a shaping material over the box frame to form the shape. The material of choice for a project like this is stretchy speaker box carpet, available at any install shop or online at www.selectproducts.com. This material is very stretchy in order to fit over odd shapes, and it can soak up a lot of resin to make the box very strong. It should only be used over solid frame structures, however, as it tends to warp weak panels. Sub boxes are a perfect application for this technique, making it a very fast and easy way to bang out a nice sub system. Why take the easy way out and make it flat when you can get some nice factory-looking curves? As always, send any questions to sbrown@alpine-usa.com and check out www.stevebrownuniversity.com for more hands-on opportunities.
 This is where we left off...  This is where we left off last month, with a skeleton of a subwoofer enclosure. |  Staple some stretchy speaker...  Staple some stretchy speaker box carpet over the entire surface of the sub enclosure. |  This is what your box should...  This is what your box should look like after you've stretched the carpet over the frame and trimmed off the edges. |
 Fiberglass resin can now be...  Fiberglass resin can now be brushed over the speaker carpet. |  After the resin has dried,...  After the resin has dried, a sheen over the surface indicates that resin has fully saturated the carpet. |  The surface of the hardened...  The surface of the hardened carpet will be very rough, so it's necessary to hit it quickly with a grinder to smooth it out. |
 Next, a layer of fiberglass-reinforced...  Next, a layer of fiberglass-reinforced body filler is spread over the entire box to fill any low spots. |  Grind down the reinforced...  Grind down the reinforced body filler to get it as smooth as possible. |  Now, we can check the fit...  Now, we can check the fit of the box to make sure we're in good shape. |
 We've decided to make a simple...  We've decided to make a simple trim panel at the top of the box to flush mount the seat back release. |  After a few tries, we have...  After a few tries, we have a cardboard template that fits the car. |  Transfer the cardboard template...  Transfer the cardboard template to 1/4" MDF and cut it out with a jigsaw. |
 Accelerator is sprayed on...  Accelerator is sprayed on the CA glue joint to quickly cure it. |  The next step is to smooth...  The next step is to smooth out the joint between the box and the 1/4" MDF trim plate with a layer of reinforced body filler. |  This type of enclosure is...  This type of enclosure is smoothly integrated with the car, doesn't take up much space and sounds excellent. |