1987 Mercedes-Benz 560SEC

Philip Petracca is an audio competitor, a 15-year veteran of the soundoff wars. He's steadily worked his way up the competition ranks, starting in 1991 with a Chevy Baretta equipped with the then-standard winning combination of an Alpine source unit, PPI amplifiers, MB Quart full-range speakers with the foundation provided by JL Audio subwoofers. His current ride, a no-compromise Mercedes-Benz 560SEC, mates classic eighties style with cutting-edge technology working in concert to provide the definitive in-car listening experience.

Currently, Petracca has what must be considered one of the dream jobs in the industry as the head of product development for XACT Communication, one of the primary suppliers of Sirius Satellite Radio hardware. He's held a number of positions with Verizon Wireless, T-Mobile and Sirius Satellite Radio.

Petracca purchased his dream ride, a 1987 Mercedes 560SEC, back in 2000 as he began competing at the national level, gaining a degree of notoriety. But a little over a year ago he decided it wasn't enough to just compete at the high-est levels-he needed to win. To do so, he assembled an installation dream team of industry veterans, Gary Biggs, Kent Buller and Mark Eldridge, who translated his radical designs into a vehicle that now rivals some of the legends of the genre.

No Compromise, No LimitsAs Petracca tells it, his car is the very rare case in which a mobile sound system installation is taken up to, and beyond, the edges of the conventional envelope. For most enthusiasts, the time, technology and finances required simply would serve as the firewall between a great-sounding car and one that could compete against the world's best. And these days, it's even rarer to experience a system that is purely dedicated to the pursuit of audio excellence.

For starters, there's no video in this system to distract attention from its audio excellence. In an era where many people believe good sound is compressed audio coming from an iPod experienced through cheap ear buds, listening to this particular Mercedes is a revelation. There was only one restriction on the design brief, not to destroy the car as it is still drivable. But while the functionality of the car couldn't be compromised, it wouldn't get in the way of the sound, whether the traditional 2-channel programming as well as all the flavors of the multi-channel world: Dolby Digital, DTS and DVD-Audio.

The layout of the system is deceptively simple. Dead-center of the radically restructured dash, sits an Alpine F#1 Status DVI-9990 AM/FM/CD/DVD-Audio source unit, the flagship successor to the legendary 7909. Two PXA-H990 processors installed in the back deck handle the signal processing chores while the trunk has been redesigned to accept six Zapco custom hand-built amplifiers: four 4-channel amps with a pair of 2-channel amps bridged into mono. One 2-channel powers the JBL W10GTi 10" sub in a sealed enclosure in the center stack while the other powers the companion W15GTi 15" sub in the ported enclosure where the rear seats once resided.

The all-important full-range speaker requirements were also filled by Zapco with an all new line of separates. Zapco, a subsidiary of ARPA of America, turned to Italy and corporate cousin ESB, for the line of hand-built separates that will form the basis of Zapco's new Competition Series. The speakers feature ESB's latest technology and will arrive at Zapco dealers in the first quarter of 2006.

Maximizing the advantage of the new drivers, the Benz' interior and trunk were gutted, giving Biggs, Buller and Eldridge a blank canvas, save for the sound deadening materials installed in the previous upgrade. Everything behind the dash was removed, including the air conditioner, all instrumentation and gauges, as well as all un-necessary wiring and other components. What was left of the factory wiring harness was cleaned up and moved so that it would allow the front stage speakers to be installed in optimal locations, in the hope of eliminating any reflected sounds.

"The specific locations and installation of the front speakers is absolutely the most critical factor in determining the end sound quality result," says Eldridge. "It is well known that a moderate-quality speaker installed properly will always outperform an ultra high-quality speaker installed poorly. In the case of the Benz, the ultra high-quality speakers were installed in the best locations, and in their optimal enclosures. That, combined with the highly modified, acoustically controlled listening environment inside the car, resulted in an incredibly good-sounding system."

"The first step in the interior design was to locate the seats as far rearward and towards the center as possible. This allows the listeners to be further from the speakers and more centered between them. This minimizes the path length difference between the left and right speakers, allowing for a more coherent wave front with minimal time arrival and intensity differences, resulting in a much more controlled and stable soundstage and spatial qualities," says Biggs.

"The next step was to make as much room as possible up front for speakers and acoustical treatments, without sacrificing the structural integrity of the car. To this end, some of the non-critical metal in the fire wall area was moved, or removed and rebuilt in a different way to allow for optimum speaker placement. The windshield wiper system was removed, which allowed a significant improvement in speaker location possibilities. The metal below the windshield line was pushed forward as much as possible to make room for the midrange and midbass enclosures. Even after the modifications, none of the crush zones or structural metal was modified," says Buller.

While discussing the system, Eldridge, Biggs, Buller and Petracca explained that the placement of the speakers eliminates the early reflections from hard surfaces near each speaker. "There is no way that any electrical signal processor can correct for acoustical problems in the listening environment," says Eldridge. "Once the signal is converted to mechanical energy and leaves the speaker as a sound wave, it is at the mercy of the acoustical environment within the listening space." The design of the system and the placement of each speaker either eliminates reflected sound or directs the energy to surfaces specifically designed to absorb these signals."

The mids were placed first. The mids are located approximately 2" below the windshield, set back approximately 10" from the front of the new dash and 4" outward from both ends of each side of the new dash structure. Basically, they're in the engine compartment. The placement process uses test enclosures optimized for each driver with the exact location determined by a trial and error process. The midbass speakers were located next in the same manner. The tweeters were located last, adjacent to their respective midrange speakers. "Minimizing the distance separation between the mid and tweeter is very critical in order to create a coherent wave front without the inherent problems of comb filtering and other acoustical anomalies created when the tweeter is distant from the mid," adds Petracca.

It's All InsideIn their effort to fully optimize the listening experience, in addition to moving the seats 6" rearward, the pedal assemblies were modified to extend through the new false firewall. A custom steel assembly was fabricated, using high-quality linear bearings. The bearings allow the two 1/2" stainless steel quick release pins, with round aluminum pedals attached to them, to be inserted. When depressed, these new pedals actuate the brake and throttle controls. (The car is fully functional, as it was driven from the Las Vegas Convention Center to the parking deck at the New York New York Casino Hotel for our post SEMA Show photo shoot.)

The steering column support structure was then redesigned to minimize its size, getting it out of the way of the sound. The gauges (see sidebar) and controls were relocated to the center console area and the factory air conditioner system was totally removed. The modifications didn't stop there (see caption on the steering wheel).

Originally the Alpine DVI-9990 was mounted below the sound quality subwoofer in the center stack but ultimately the faceplate was relocated to a central location above the sub for better visibility. Behind the gauges and remote in the center console are a bank of switches to control important system functions: trunk open/close, system neon lighting, parking brake actuator, system and interior fans, audio system configuration (SQ only, SQ + SPL sub or SPL sub only) and hazard lights.

The rest of the interior is totally custom, but the modifications certainly can be characterized as low key. While it certainly isn't an OEM style, it isn't over the top as is often the case in show cars at this level. The primary goal, while using a variety of materials (paint, Ultraleather vinyl, suede, alligator skin, carpet, grille cloth and some tasteful aluminum details) and construction techniques, was strictly to optimize the listening experience. The cumbersome Mercedes OEM seats were discarded, replaced by Sparco sport seats reupholstered by Southeast Auto Trim in Tulsa, OK.

Behind the seats, the rear panel showcases the 15" JBL subwoofer, which seems to almost float above its enclosure. Petracca noted that throughout the installation, there are no visible fasteners. All fasteners are hidden behind trim pieces, OEM-style, to help with the overall clean appearance of the installation.

Import TuningAbove the subwoofer, flush-mounted into the rear deck, the pair of Alpine PXA-H990 processors are mounted between the rear speakers. Each speaker in the system is on a dedicated signal processing and amplification channel. No passive networks are used in the system.

The crossover points for the system are set at 2.8kHz between the mids and tweeters, 260Hz between the midbass and mids, and 80Hz from the sub to the midbass drivers. The crossover slopes vary from 12dB/octave to 36dB/octave, depending on what yielded the best sound quality for each set of speakers.

Signal delay is used only to align the speakers in each channel (i.e., the left tweeter, mid and midbass are all aligned, as are the center mid and tweeter, etc.). There is no differential delay between left and right channels. Because of the attention to detail in the design and installation of the speaker system, a differential left-right delay would not improve the sound quality from either seat.

The system required very minimal equalization, again due to the attention paid to the speaker system installation.

Employing Alpine's PXA-H990, the install team spent 60+ hours tuning over a six-week period and found the DTS Neo algorithm provided the best overall sound quality. Compared to the traditional 2-channel setting, it added additional space to the left and right sides of the soundstage, additional depth and a better sense of ambience. This is not to say that DTS Neo will work best in all systems. Every system design is different, and it is likely that one of the other settings may work better in a different vehicle.

The past 15 years of competition has rewarded Petracca with lifelong experiences and friendships. For him the best part has been seeing new people entering the hobby and bringing new outlooks and techniques that keep the old timers on their toes. He says, "The best advice I could give to a newcomer would be, get involved in our hobby for the love of music, cars and meeting people. If you do this for awards and accolades alone, the end result of your experience will not be nearly as rewarding."

HVAC + GaugesThe system takes a novel approach to ventilating the car during judging. Since running the engine is needed to run the HVAC system, Petracca has employed an external system to keep the car cool in summer and warm in winter.

Under the left rear trunk area are mounted three 2" diameter ventilation connectors. One connects to the left B-pillar vent, one to the right B-pillar vent, and the third to the amplifier rack area.

When at shows, a small home window-type air conditioner, run off a 120-volt AC supply, can be connected to the vent system to blow cold air into the interior and to the amplifiers. A return air duct extends from under the driver's seat area back to the window unit to complete the air conditioning system.

This allows the car to remain cool and comfortable inside when at a show, without having to run the engine. A second option that can be used when driving uses a small fan box, designed to attach to the three vent connectors. It takes fresh air from outside the vehicle and blows into the interior and amplifier area.

One additional detail caught our eye when sitting in the car-the new gauges located in the center console. Their elegant faces are in keeping with the overall interior concept. The gauges for speed, RPM, fuel level, oil pressure, water temperature and voltage are custom built by Classic Instruments (www.classicinstruments.net). Tom Gale, former vice president of design for DaimlerChrysler led the design team that produced these stunning gauges. The gauges have a unique look of spun metal and the center dial portions are precisely color matched to the car's theme. The gauges are hand built and have innovative design features such as curved glass lenses that flow into the contours of the stainless radial bezel. They accent the style and setting of the interior perfectly.