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.