| trucktronics electronics
With factory audio systems harnessing more and more popular features found in aftermarket products, integrating peripheral audio equipment with the factory source unit has become an accepted option. In Truckin' Volume 33, Issue 8, "Integrating with OEM, Part 1," we touched on interface solutions for connecting aftermarket products, such as iPods and MP3 players, along with interface solutions for steering-wheel volume controls, video, and head unit swaps. In this issue, we'll cover an OEM integration that allows you to keep the factory source unit intact while you upgrade your amplifier and speakers.
Sound Decision
Many of today's factory head units are loaded with conveniences and features you like, so it makes no sense to replace them for comparable aftermarket pieces. The decision to replace may be further compounded by the assimilation of the factory unit, many of which have become so seamlessly integrated with the dash that replacing them could require a great deal of customization and/or alteration. If you're reading this column, the chances are you are looking for a solution to upgrade your amplifier and speakers with high-quality aftermarket gear. To do so, you'll have to get integrated.
Connecting
There is one outlining problem in connecting a radio-back system to your factory source-the signal outputs. Factory head units are not equipped with RCA outputs-a low-level and low-voltage signal used by aftermarket audio electronics. In most cases, the only signal available is an amplified and high-level one. To rectify this, a high-to-low level converter can be used, but beware: Not every converter is right for every system. If you want your high-performance aftermarket audio products to really perform, you need to use the right OEM integration piece.
If your ride came equipped with the standard audio package, integrating your aftermarket amps should be relatively simple. Most standard audio systems consist of four channels of operation. Adapting aftermarket amplifiers into this system can be done by using a simple line-level converter, such as a standalone unit or one built into an amplifier, and then tapping into the factory speaker wires. This will supply your amplifier with a usable low-level input signal.
But what do you do if your vehicle is equipped with the multi-channel audio upgrade package from the factory? This is where things become more complex. For example, let's say the factory system consists of a three-way speaker system in the front with six amplified channels powering those speakers, or one amplified channel per speaker. Naturally, this system will use a crossover network as the speaker system will consist of a pair of tweeters, midrange, and woofers. Because of this, simple line-level converters will not be very useful-unless your speakers require the exact same crossover points as the original units, which is highly unlikely. In order to get a useful signal, the three channels, left and right, must be summed into a stereo pair. Summing the channels will provide a signal that covers the full audio spectrum, rather than the individual crossed-over segments from each of the six original channels. Products such as AudioControl's LC6i and LC8 provide this basic channel summing capability for a variety of applications.
However, factory offerings have more up their sleeves. Nowadays, it's common that systems-or more commonly, the factory upgraded "hi-fi" systems-use digital sound processing (DSP). Basic DSP consists of equalization, a means of improving the sound quality by altering the frequency response of music. Equalization is used because speakers are seldom naturally smooth throughout their frequency band, and the acoustical challenges of a vehicle will further alter their response. By adjusting the levels of certain frequencies, the sound of the system can be made much more lifelike. But, that does not translate well after adding aftermarket component speakers that are much more natural sounding to begin with. In order to take full advantage of your new speakers' sound quality, you first need to get rid of the inherent equalization of the factory audio's signal. This can be accomplished by using such integration tools as JL Audio's CleanSweep. The CleanSweep uses a specific test CD that contains a battery of test tracks to flatten the frequency response from the factory head unit before it gets to the amplifier(s). This fully automated process takes just minutes and the results are amazing.
The most advanced factory head units use DSP to the fullest extent, adding time corrections to each channel in the system. Time correction, or delay, is used to right the time domain of each speaker. Why is this important? Take for example, our three-way system from prior. Each of the three speakers that make up the left and right channels are located in different areas of the cab. In order to make them coherent with one another, each must reach the listener's ear at the same time. In most instances, tweeters are mounted up high and closest to the listener. Since they are the closest drivers, the audio signal to them is delayed ever so slightly to match appropriately with the midrange and woofers. This is important to a system so the audio output closely matches the original intentions of the artist in terms of soundstage. But, this again becomes a nuisance when adding aftermarket equipment to the factory source, particularly if you are channel summing and/or changing the location of the speakers. But, worry not, the aftermarket has you covered here, too. Products such as Rockford Fosgate's 3Sixty and JBL's MS8a take into consideration time corrections, as well as channel summing and equalization, which make them highly powerful sound processors.
Working with factory audio/video equipment is always a challenge. Car audio dealers and their installers are always trying to figure out how to tap into the new vehicles, while aftermarket manufacturers continue to show their support helping dealers with useful tools to upgrade virtually any audio system. OEM integration components will continue to evolve and allow installers to upgrade your amplifier and speakers to provide you the improved sound you just can't find with factory offerings.
