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Making the Best Better

Owners of Mercedes Benz vehicles know the meaning of luxury car. But what happens if the owner feels that a portion of the vehicle’s functions are not up to par. Would it be sacrilegious to try to make that lacking function better?
The owner of this 2003 Mercedes Benz CL500 two-door was more than pleased with just about every aspect of the car. The only function that he found deficient was the audio system.
What he wanted was more bass. But upgrading a Mercedes Benz CL500 presents all sorts of problems. Any attempt to do anything that could affect the factory radio could cause a whole lot of problems. The factory radio is integrated with the car’s computer system. And the factory amplifier is specifically designed to work with the factory radio. So any upgrade attempt would have to figure out a way to keep every thing intact and still be able to add more bass. Moreover, the controls for the audio system are on the steering wheel. The owner did not want to lose any ability to control the audio via the steering wheel controls and via the menu options that appear on the radio’s screen when he is setting parameters for how the system is to perform.
He took the car to Sounds Good Stereo, Woodland Hills, California. The owner, Isaac Goren, took a lot of time studying the layout of the OEM system and did a lot of research as well. He also probed and tested wiring and researched adapters on the market that could be used to make things work. This is what he was able to come up with.

All Functions Remain With More Bass
Goren decided it would be possible to replace the factory subwoofer with a Rockford Fosgate 12-inch free air subwoofer and to use a JL Audio 500/5 five channel amplifier to power not just the subwoofer but also the rest of the factory system.
The factory amplifier remains in the vehicle. Without disconnecting this piece, Goren took the signal coming out of the factory amplifier and routed it through a Pacific Accessory Corp (PAC) OEM2 adapter. From the adapter, Goren used ordinary RCA cable to carry the signal to the JL Audio 500/5 amplifier. The front and rear fader of the factory radio still works and the electronic crossover of the JL Audio amplifier is being used to work the factory speakers in the front and rear of the vehicle and the Rockford Fosgate subwoofer. The tweeters are being crossed over by the factory amplifier.
A JL Audio RPC-1 control knob was mounted under the dash near the driver’s seat to control the volume of the subwoofer.
The driver’s ability to adjust the parameters of the car’s surround sound remains intact. The factory amplifier remains intact as well and still is integrated with what it is supposed to be integrated with.
The JL Audio 500/5 five channel amplifier has the following power rating: Front channel -- 100 watts x 2 at 1.5 ohms to 4 ohms; Rear Channel -- 25 watts x 2 into 1.5 ohms to 4 ohms; Subwoofer Channel -- 250 watts x 1 into 1.5 ohms to 4 ohms. The front crossover is fully variable and can be set between 50 Hz. and 5 kHz. It also features a selectable slope of 12 or 24 dB per octave at bandpass or highpass. The rear crossover is highpass, is fully variable and can be adjusted between 50 Hz. and 5 kHz. It has a selectable slope of 12 or 24 dB per octave. The subwoofer crossover is fully variable and can be set between 40 Hz. and 200 Hz. It is a lowpass crossover with two selectable slopes, 12 or 24 dB per octave. The amplifier also includes a Bass EQ which offers a variable boost up to 15 dB and a defeatable infrasonic filter with a 24 dB per octave slope at 30 Hz. to protect the subwoofer.
The PAC OEM2 has its own gain adjustments and can balance the signal going from the radio to the amplifier.

The Install
Goren wanted the installation to be as stealth as possible. Moreover, he wanted the owner to have the ability to turn everything back to factory if and when he was ready to sell the vehicle. This meant that Goren was committed not to affect factory panels and such in the installation of the upgrade.
One example of how he was so careful about this can be seen in how he mounted the JL Audio amplifier. He thought that the trunk would be the best location for the piece. So he took the rear panel in the trunk that is behind the back seat and gas tank and removed it. He then secured a 3/4-inch medium density fiberboard to the floor of the car in this location and siliconed the board against the gas tank. He then re-mounted the factory panel on top of the board and then mounted the amplifier to the panel.
The rear deck was removed to gain access to the factory subwoofer and the factory subwoofer was removed. The Rockford Fosgate subwoofer had been chosen partially because it is pretty much the same configuration as the factory subwoofer. Moreover, it plays very well without a box. The factory subwoofer is not mounted in a box.
Once the factory subwoofer was removed, Goren put dampening material on the rear deck to assure that there would be no resonance or rattling and then he constructed a template out of medium density fiberboard to match the layout of the factory opening. He mounted the subwoofer into the template and then mounted the template on to the rear deck.
The Rockford Fosgate subwoofer falls about 4-inches lower than the original factory subwoofer, but it does not really effect the available space in the trunk.
A relay was added directly off of the ignition to turn the JL Audio amplifier on and off. So when the driver turns on the ignition, the JL Audio amplifier turns on. The factory amplifier is turned on through processing of a data cable.
In his research and probing, Goren found that there was a data cable that “spiked” the audio system at times when it passes signals. The “spike” caused by the voltage of the signal could shut the JL Audio amplifier off for a short time when the audio is listened to very loud. In addition, this particular cable is tied to the factory speed sensor, so when the car changes speed, it could turn off the JL Audio amplifier. So, Goren disconnected this cable to assure that things work properly.
It should also be noted here that Goren found it necessary to solder connections between the factory amplifier and the PAC OEM2
A fuse block was mounted next to the battery to protect the installation.  

Rob,

Great post!  Believe it or not I am in the same position as the CL500 owner.  Unfortunately I went to a shop not as good as Isaac's and they just put a box in my trunk and barely cut out the factory sub.  

I'd be very interested in any pictures there might be of the sub installation.  Could you please post them or email them to me (gmd@redknightholdings.com).  Esp how the brace was installed and how the sub was connected.  I already have a JL 500/1 amp in stalled, but I need to remount a new subwoofer so that I actually have bass again!  

Thanks,
Gareth