A method is provided for correcting errors in the overall reproduction characteristics of an audio system installed in a residence. The method may include the steps of generating a test signal as an input to the audio system and converting the resulting sound generated by the system and its room environment into stored data whose values are a function of the sound. This data is then transported from the residence of a processing center. At the processing center, the stored data is read and utilized to fix the characteristics of an equalizer such that when it is installed in an audio system, it will give the desired correction to the output thereof. Thereafter, the resulting equalizer is transported to the residence and installed in the audio system.