If you are to look at any system that has a serious car stereo in it you will most likely notice that most have a digital sound processor. The first time I saw one of these I thought it was just an overpriced bass boost, and that my current amp would basically do the same thing. Little did I know that a bass processor is much more than a bass boost.
A bass processor is installed before any crossovers or signal processors. So it would be hooked up right after your in dash unit. Always install before your crossover. At first you might think that a bass processor would be just for bass heads. This is not the case a bass processor can also improve the low end sound of all music from classical to rap. So what exactly does it do?
A good bass processor contains a circuit that accurately recreates and injects low frequency information back into the signal, giving your bass more impact. A bass processor will also allow you to customize this low end power to your specific vehicle. It does this by allowing you to control the para-bass functions. What this does is allows you to adjust the sweep and the width of the bass.
The sweep will let you pick a certain frequency you want the bass restoration circuit to maximize. Having a lower sweep the bass will be centered around lower frequencies. While having the sweep higher means it will be centered around a higher frequency. While the width allows you to control how wide of a frequency range it will effect. If you have the width low the bass will be centered around a smaller frequency range, and turning this up higher will increase the frequency range.
So with all this bass processing going on you might be worried about your expensive subwoofers. I know that is something I was worried about when I first installed a "epicenter" by Audio Control a popular bass processor. I was mainly worried about the subsonic frequencies that can damage your stereo equipment.
If you look at any good bass processor will come with what is called subsonic filter. Subsonic frequencies are those that are not audible to the human ear. Sound frequencies that are below 20Hz are considered subsonic. A good bass processor will have a subsonic filter that will make sure you do not waste your car stereo's power on this subsonic information and will make sure you are putting all of your systems power to good use.
A subsonic filter is a huge feature to being able to fine tune your bass response. On most systems setting this filter at 33Hz will be good. If you want to protect you're your speaker system even more though you can try a higher frequency. Often a higher frequency will sound louder and cleaner.
So wherever your interest is in Beethoven's kettle drums, Miles Davis' trumpet, or the percussion of rap music, a digital bass processor will restore those long lost bass notes.