Stealth Attack - Brax Helix 2009 BMW x6

When you hold a senior position in a company there are the occasional perks that come along with that. Let’s just say for example that you were the President and CEO of a car audio manufacturer like, oh, I don’t know, say Rockford Corporation, and you had just signed a deal to distribute a high end brand of electronics and speakers in the US. Perhaps you’d be able to convince some industry veteran installers to install some of that product in your personal ride? You know I am setting you up of course, and for Bill Jackson, President and CEO of Rockford Corporation, the Brax system you see in his 2009 BMW X6 came to fruition in that exact way.

Industry veterans Brian Schmidt of Mobile Solutions and Doug Dobson were tasked with the build. As this vehicle is leased, it couldn’t be chopped to pieces to achieve the goal of showcasing the product and sounding great. Their decades of experience made this a relatively easy task.

Stealth Attack - Brax Helix 2009 BMW x6For the front sound stage a Brax Matrix 3-way component system (M3CPP) was chosen. The component set consists of a 1” silk dome tweeter, a 54mm silk dome midrange and 6 ½” midbass. The tweeter pod was a custom creation, as the stock BMW tweeter was much smaller. ABS plastic, long-strand fiberglass and plastic body filler formed the foundation before being treated to a finish that mimics that from the factory. The door panels were modified for the midrange and midbass drivers. A dedicated opening for the 6 ½” in the lower part of the door needed to be created. The challenge was to maintain the factory look as much as possible. They accomplished this by creating an opening in the factory map pocket for the sound to pass through and then fabricating an aluminum trim ring with custom stamped grill to cover the opening. The final element of the front stage fabrication was to replace the factory center channel with a Brax midrange (Matrix 3.1).

For rear fill, two sets of Brax component speakers were installed in both the rear doors and rear cargo area. Again trying to maintain a stock look he utilized the factory speaker location in the rear doors to mount a Brax 3” midrange (Matrix 3.1) and Brax 1” tweeter (Matrix 1.1). As with the front doors, they used the original factory midrange as a template to fabricate a mounting plate for the Brax Matrix 3.1 driver. Then, after modifying the mounting location of the factory tweeter a second mounting plate for the 1” soft dome tweeter was fabricated.

The rear cargo area speakers were replaced with another set of the Brax 3” midrange and 1” tweeters (Matrix 3.1 and Matrix 1.1). Slight modification to the original factory mounting brackets allowed them to be re-used for the new speakers. To ensure maximum reliability and best audio signal possible all new Rockford Fosgate speaker wire was run from the crossover locations to each speaker location. This of course presented its own challenges in trying to run multiple speaker wires through the doors wiring boot – but patience and persistence made it all come together.

To compliment the mids and highs, the team knew they had to provide an equally matched low frequency system. To accomplish this they chose to use four Brax 10” subwoofers (M10.1). These woofers work well in small sealed enclosures, which allowed their installation in the factory spare tire location. A Stealth Attack - Brax Helix 2009 BMW x6framework was constructed out of MDF to utilize as much of the available airspace as possible. Since the vehicle battery is also housed in this compartment they had to construct a frame around it to maintain access for servicing the battery if needed. Once the framework was complete and fully reinforced, it was taped off in preparation for the creation of a fiberglass bottom for the enclosure. After building up multiple layers of resin and chopped mat, the enclosure was removed for the installation of the top panel to which the woofers are installed.

A custom trim panel was then created to surround the woofers and finish off the cargo area bringing the final surface back to the same level of the original floor. Multiple layers of MDF trim out the woofers giving them a recessed finished look. An access for the factory battery for servicing ability was integrated into this final trim.

Brax Matrix 2 channel (MX2S) and 4 channel (MX4S) amplifiers were the most logical choice for the system. The MX2S is used to power the woofers and the MX4S for the mids and tweets. These amplifiers presented their own challenges to the installation, both from a size and weight standpoint.

Measuring 13” square and weighing in at over 20 pounds each, the amp rack had to be structurally strong enough to support them but, not visually overpowering compared to the rest of the install. As the X6 already had a rail system in the floor of the cargo area, they made use of that to mount a custom aluminum rack that would suspend the amplifiers just behind the rear seat.

The side supports were machined out of aluminum in-house at Mobile Solutions and support a 1-inch square steel frame to which the pair of amps and four large passive crossover networks are mounted. The passive networks allow for a great deal of flexibility in system tuning, so making them accessible was important to the final performance of the system. All cabling to and from the amps is neatly wrapped in wire loom and tied off to ensure reliability.

Stealth Attack - Brax Helix 2009 BMW x6

Since the X6 utilizes the BMW I-drive system, removing the factory radio wasn’t an option as it also integrates the navigation system, hand-free calling and vehicle feedback systems. The other challenge is the audio output of the BMW radio. Audio signals are sent throughout the vehicle via fiber optic cables. To overcome this, a Motus Lab AGW+ interface was used to translate the fiber optic signal into an analog signal while retaining the factory fiber optic loop. Once Stealth Attack - Brax Helix 2009 BMW x6converted, the analog signal was then directed into a Rockford Fosgate interactive signal processor (3Sixty.2). The 3Sixty.2 allows for full graphic equalization of the system and addition of delay to correct for any time alignment issues that weren’t overcome during the installation of the speakers. This allows for precise tuning that results in the creation of a wide soundstage with correct imaging - key elements to a premium sound quality system.

If you are painting a mental image of the system diagram in your head, then you are perhaps questioning how a four channel amp can power so many speakers. With the 3sixty.2 in the system, flexibility and control is easy, when you have enough amplifier channels. The installation team snuck one of the new Rockford Boosted Rail Technology amplifiers 4-channel (PBR300X4) into the system to drive the center channel and the rearmost speakers. This diminutive amplifier has a footprint of 6.75 x 4.25 inches, allowing it to be concealed easily, yet it’s efficient design lets it crank out an effortless 75W per channel.

The vehicle itself remains stock in terms of drivetrain – but that doesn’t mean it isn’t potent. Equipped with a 4.4L V8 that has a pair of twin-scroll turbos strapped to it, the engine produces over 400hp and more than 450lb-ft of torque between 1800 and 4500 rpm – that’s some serious twist! Power is sent to all four wheels and to the ground through 22-inch wheels wrapped in 275/40 and 315/40 rubber. Even with the audio system on board, Jackson’s bimmer can run to 60 in under 6 seconds.

While the system is relatively simple in design, that doesn’t mean that its execution didn’t take a great deal of planning and creativity. I personally like systems that are custom, while simultaneously looking like they belong. Hmm – perfect motivation to get started on my own ride!


Essentials // Owner: Bill Jackson • Location: Tempe, Az • Vehicle: 2009 BMW x6


Audio and Multimedia // Front Stage : Brax Matrix 3 way components (m3cpp)/ Brax 3” midrange center channel (martix 3.1)• Rear Stage: Brax 1” Tweeter (martix 1.1) | Brax 3” Midrange (martix 3.1) • Back Fill: Brax 1” Tweeter (martix 1.1) | Brax 3” Midrange (martix 3.1) • Subwoofers: 4 ea. -Brax 10” subwoofer (M10.1) • Amplification: Matrix 2 channel (mX2s) | Matrix 4 channel (mX4s) | Rockford PBR300.X4 • Processing: Rockford 3sixty.2 | Modus Fiber optic Interface • Power Cable | Rockford Fosgate power cable, Distribution blocks and interconnects

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