"My whole goal with my car was to have a clean and custom system but yet reflect or look as close to factory as possible," says Bob Hohenstein of his '06 Pontiac GTO. Custom and factory together in one ride? Hohenstein may appreciate the stock styling of this 400hp all-American vehicle, but as an instructor at the Acoustic Edge Institute, creating one-off systems is a passion. Therefore, the build, though very customized, tries its best to look stock - just do your best to ignore the subs embedded in the rear panels!
Tech:Wheels: MRR Design GT-1 19" x 8.5"Tires: Falken AZENIS 235/35/19Exhaust: Corsa cat-back exhaustSuspension: SLP lowering coils
Shop:Installer 1: Chad ParedesExtreme Audio SystemsHonolulu, HI
Installer 2: Earl ShimabukuroIsland Sound CustomsHonolulu, HI
With 400hp and 400 lb-ft of torque from the GM LS2 engine, the GTO's performance was more than satisfactory. Hohenstein merely had the car lowered, put on a cat-back exhaust from Corsa and got new wheels from MRR Design. |  |  |
Working mainly at night at the Acoustic Edge Institute, Hohenstein pulled everything out of the car but the dash in order to pad rattle-prone areas with damping material. "Pontiac did a great job on making a quiet car," he says. The dash remained as it was, other than the simple addition of a Soundstream VIR-7850 head unit and the MPQ-GXO parametric EQ beneath it. Hohenstein used 3M Ready Mix to mold both of these pieces into the dash. | 
After routing the Soundstream wires under the car or bundled beneath the carpet, the interior went back in, including a Soundstream PQ7 7-band equalizer/crossover. "It's always nice to have as much control over a signal as possible," Hohenstein relates. "Every song is different and having more than one EQ can definitely fix any holes or peaks that were recorded in the music." The MPQ-GX0 in the dash feeds up to 10 volts RMS to the secondary EQ, which Hohenstein nestled between the reupholstered back seats, along with a PowerPlant 2 capacitor. It only took a little cutting and trimming to tuck the piece into the new black leather. For some style, he took a center cap from the factory wheels and molded it above the EQ and capacitor with some fiberglass and 3M Ready Mix. | 
For that factory look, Hohenstein didn't want to encroach upon the vehicle's cabin space. But, he still wanted to place four 10" Soundstream T-4 subs in the cabin. The answer was fitting the ported enclosures in the rear quarter panels. "I didn't want a real boomy sound from four 10s," Hohenstein reveals, "so each enclosure is about 1.5ft3 net ... [which] is half of what Soundstream advises." Another choice was making everything removable: "I didn't want to just start fiberglassing a box into my car," he says. Each 0.75" thick enclosure was built by making two halves that he patched together with fiberglass. A trim panel then wraps around the B-pillar, C-pillar, seats and windows. The subs hold this panel down and red suede trim covers their mounting screws. "Looking at the port you will see another trim that is silver," Hohenstein adds. "That piece serves as a form of aperiodic dampening material to help flatten out the response of the woofers." |
The GTO holds a total of five component speakers - Soundstream Reference Series RF-60C's. The first set is housed in a super thick (we're talking 0.5" or more) enclosure made of fiberglass, Duraglas and MDF. After fabrication, Hohenstein further reinforced it from the inside with a mixture of Duraglas and fiberglass resin. "All of my enclosures are extremely dense and free of any resonance," he says. He wanted these speakers to create the center stage along with Soundstream 25mm silk-dome tweeters that replace the factory tweeters on top of the dash. | 
Hohenstein really liked the shape of the front doors, in particular the top halves. Unfortunately, he couldn't keep the panels and integrate all the new gear. So, he made a plaster mold of the front door panels in order to create fiberglass replacement parts with the exact same shape. "There is very little MDF in the door itself," Hohenstein reveals. "I constructed it mostly out of fiberglass for weight purposes." The bottom panel houses two 6.5-inchers trimmed in painted acrylic, which hides the mounting screws. The rest of the components are in the new rear deck enclosure made of MDF. "The tweeters were placed in a fashion to help push the midbass forward," Hohenstein says. |  |
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Two 300-pound actuators motorize the trunk open, revealing the 17-inch Soundstream monitor in the lid, which along with the 7-inch monitors in the doors, is controlled by the Soundstream VAV-4 wireless audio/video controller in the trunk. With the gas tank down here, the four amps and the two 40-farad capacitors below had to get friendly with each other. Hohenstein created racks out of aluminum, steel and MDF with a special design that runs the wires through the racks and into the bottom of the amps for a wireless illusion. Some people even ask Hohenstein if the amps are dummies, but no, the two TRA1400.2's on the bottom and the TRA960.4's on top are definitely live. "For clean power everything runs at 4 ohms," he says. Hidden beneath the amp, a rack holds the 10 passive crossovers from the component sets. |