A series of PC software makes the acoustic correction in the room. I'm looking for such free software to test it. For example, the sound that comes from the LoudSpeacker it hits walls, floors, ..... One part is reflected and sums up with the speaker wave. There is a problem with how to change the speaker wave(signal), as a result of summations with reflected waves give the desired wave. Why does the car subwoofer have a bandwidth of its narrow bandwidth? From https://en.wikipedia.org/wiki/Subwoofer "The typical frequency range for a subwoofer is about 20–200 Hz". Such a loudspeaker could "play" a wider bandwidth, but the acoustics would be too bad. This algorithm if I find it somewhere, I intend to implement it on the microcontroller.