In some automobile audio systems, processing is applied to the audio signals provided to each speaker based on the electrical and acoustic response of the total system, that is, the responses of the speakers themselves and the response of the vehicle cabin to the sounds produced by the speakers. Such a system is highly individualized to a particular automobile model and trim level, taking into account the location of each speaker and the absorptive and reflective properties of the seats, glass, and other components of the car, among other things. Such a system is generally designed as part of the product development process of the vehicle and corresponding equalization and other audio system parameters are loaded into the audio system at the time of manufacture or assembly.
Conventional automobile audio systems, with stereo speakers in front of and behind the front seat passengers, include controls generally called fade and balance. The same stereo signal is sent to both front and rear sets of speakers, and the fade control controls the relative signal level of front and rear signals, while the balance control controls the relative signal level of left and right signals. While fade and balance control permit users to modify some aspects of the automobile audio output, conventional automobile audio systems do not allow users to make additional modifications to the audio output, such as center image placement, stereo image width and/or presentation of uncorrelated content. These limited controls can hinder the user experience.