The subwoofer enclosure, which houses six powerful woofers, was fabricated entirely from Baltic Birch plywood and aluminum. The wall thickness of the subwoofer enclosure was 75mm (2.953 inches) thick. The total weight of the enclosure was estimated to be 1,299 N (292 pounds). The rings that mounted the loudspeaker transducers face-to-face were 31mm-thick 6061-T6 aluminum, and the plates for the binding posts were machined from 1/4-inch-thick 6061-T6 aluminum.
Fabrication Of The Overhead Electronics Console
I chose to fabricate the overhead electronics console from fiberglass composite comprised of woven roving because of its high specific stiffness and strength. The use of fiberglass composite allowed the creation of a complex shape that flowed around the ribbed supporting structures in the roof of the vehicle. This shape created three, large recessed areas, and thus prevented the electronics from protruding excessively into the overhead space of the front cockpit. In areas of greatest stress, the thickness of the composite structure was increased, and in some places exceeded 3/4-inch (19.1mm) thick. The bare fiberglass composite console weighed 276 N (62 pounds), and with all of the electronics mounted, weighed about 454 N (102 pounds). The following figures show the various stages of fabrication.
 1. The OEM headliner was used...  1. The OEM headliner was used as the basis for the mold. High-density fiberboard and duct tape were used to create the basic shape. |  2. The overhead electronics...  2. The overhead electronics console structure was removed from the mold after about six layers of 6-ounce woven roving were applied using polyester laminating resin. |  3. To build up the composite...  3. To build up the composite structure thickness rapidly, layers of 48-ounce woven roving were used. Layers of Cascade Audio's VB-FD were incorperated into the composite to provide the structure with internal damping. |
 4. The finished structure...  4. The finished structure was "bedded" into the structural ribs in the automobile's roof using Evercoat's Triger Hair fiberglass-reinforced filler. Eight mounting locations were established, and the structure was held to the roof using eight M8 socket head cap screws (SHCSs). Eight rivet nuts, each with pullout strength of 15.7 kN (3,522 pounds), were installed in the roof structure to receive the screws. To prove this console possessed sufficient strength, two adult men, each 788 N(175 pounds), jumped up and down on the structure without any apparent damage. |  5. View of the mounting surfaces...  5. View of the mounting surfaces of the composite structure prior to the application of fillers. |  6. The factory wiring routed...  6. The factory wiring routed down to the foot wells and back up the B-pillars. This removed all 12-volt wiring in the vicinity of the A-pillars, down which the loudspeaker cables would be routed. Twelve- and 14-gague GXL primary wires were purchased to match the OEM colors and, where appropriate, were striped to match the OEM colors. All connections were soldered with WBT's silver solder and protected with heat shrink tubing. the bundles of wires were wrapped with friction tape to match the OEM wire bundles and then secured with aluminum foil tape and/or nylon ties, whichever was appropriate. |
 7. the finished structure...  7. the finished structure was cut into a more refined shape. flat surfaces were created using Evercoat's Tiger Hair fiberglass-reinforced filler. |  8. A piece of plate glass...  8. A piece of plate glass was used to press out Evercoat's Tage Gold body filler to create flat surfaces. |  9. Aluminum plates were "bed-ded"...  9. Aluminum plates were "bed-ded" onto the backside of the structure using Evercoat's Tiger Hair fiberglass reinforced filler. |
 10. Each of the aluminum plates...  10. Each of the aluminum plates was drilled and tapped with M4 x 0.75 through-holes for mounting audio components and peripherals. |  11. The audio components and...  11. The audio components and the fused distribution blacks were carefully arranged to accomplish many objectives. First, the Alpine PXI-H990 Multimedia Manager (lower left) and the fused dristribution blocks (lower right) were arranged to provide access sunvisors in the headliner. An elliptical cutout in the headliner would provide access to the amplifers' fuses. the arrangement of the amplifiers allowed for the shortest possible interconnects and loudspeaker cables. |  12. The 12-volt power wires...  12. The 12-volt power wires were mounted on the backside of the consule to keep the music-carrying cables on the front side free from interference. |
 13. The high current carrying...  13. The high current carrying power cables were distributed and fused using Stinger's fused distribution block (right). The low current carrying power cables (head unit, processor, and other 12-volt accessories) were distributed and fused using Blue Sea System's fused distribution block. Because the fiberglass composite structure is electronically non-conductive, the generously raadius-ed holes for the wires didn't need grommets or strain relief. |  14. Genesis provides these...  14. Genesis provides these protective ferrules for the power connections. These prevent the setscrew from damaging the fine strands of wire in the cable's conductor. |  15. Each amplifier was mounted...  15. Each amplifier was mounted using four stainless steel M4 x 0.75 button head socket head cap screws with washers and lock washers. The Genesis Dual Mono Xtreme is shown with the fan wire (red), ground wire (black), positive wire (white), and the remote turn-on wire (blue) connections made. Note that it was later determined that the fans weren't needed. |
 16. Six Kimber Kable KCAG...  16. Six Kimber Kable KCAG silver interconnects were terminated with WBT's WBT0108 Topline RCA connectors for the front soundstage. The wiring for the console is shown almost complete, except for the loudspeaker cables. |  17. Remote turn-on and other...  17. Remote turn-on and other power wires from the overhead electonics console were terminated with high-quality automotive plugs made by Weatherpack, which are available at most NAPA automotive stores. Each of the wires had labels that were heatshrunk into place. Note that these wires were pulled out of positon for photographic purposes only. |  18. The audio components and...  18. The audio components and peripherals were dismounted and the overhead electronics console was mounted into the vehicle. The power connections were made (without fuses, of course) and the console is shown ready to accept the components. |
 19. the audio components,...  19. the audio components, interconnects, and loud-speaker cables were installed. Note that whenever an interconnect is in the vicinity of a loudspeaker cable, it crosses at a right angle to the loudspeaker cable. Also note how the loudspeaker cables neatly flow from the amplifiers down the A-pillars, with no other wires in their vicinity. | | |
Resources
1.ANSI A208.2-2002, Grade 140 specifications, see http://www.plumcreek.com/downloads/mdf/med_density_mdf_specs.pdf
2. Typical density of 745 kg/m3 reported, see http://www.uniboard.com/panels/trade/brands/panfibre/technical_specs/
3. Typical property of E-glass chopped strand mat/unsaturated polyester resin, 25.0 weight-% fiber, see http://www.azom.com/Details.asp?ArticleID=1453#_Typical_Properties_of
4. Derived from 25.0 weight-% fiber, where the density of the glass fiber and the resin was 2.6 and 1.3 g/cm3, respectively, see http://en.allexperts.com/q/Composite-Materials-2430/fiberglass-1.htm
5. Typical property of E-glass woven roving/unsaturated polyester resin, 37.7 weight-% fiber, see http://www.azom.com/Details.asp?ArticleID=1453#_Typical_Properties_of
6. Derived from 37.7 weight-% fiber, where the density of the glass fiber and the resin was 2.6 and 1.3 g/cm3, respectively, see http://en.allexperts.com/q/Composite-Materials-2430/fiberglass-1.htm
7. APA-The Engineered Wood Association, Voluntary Product Standard PS 1-07 Structural Plywood, Feb 26, 2007, p. 45, properties for Species Group 5 reported, see http://www.apawood.org/level_c.cfm?content=pub_ply_libmain
8. See http://www.atmlist.net/pipermail/atm/2004-December/005401.html
9. J. E. Shigley, Mechanical Engineering Design, 3rd Ed., McGraw-Hill, p. 636, 1977.
10. See http://www.me.umn.edu/education/courses/me5221/Lab/fea1plate.html