33Basic operationHow to operate the Sound Adjustment ModeAbout Sound Adjustment ModeThe system has several features that allow you to adjust the acousticcharacteristics inside the cabin. In the Sound Adjustment Mode, thefollowing characteristics can be adjusted.CrossoverThe frequency band that is stored by audio media such as CDs is afairly wide range from 20 Hz to 20 kHz, and it is difficult for a singlespeaker to be able to play back all frequencies in such a wide range.Because of this, several speakers can be used, with differentfrequency bands (such as treble, medium and bass) allotted to eachspeaker so that wide frequency ranges can be played back.The "Crossover" function is used to allot the frequency ranges thatare to be played back by each speaker in accordance with theinstalled speaker units and the layout of the speakers, in order toobtain the maximum level of performance from the speakers and toprovide the most stable frequency characteristics.The crossover function includes a high-pass filter (HPF) for playingback treble sounds, and a low-pass filter (LPF) for playing backbass sounds. In addition, the HPF and LPF are used in combinationin order to play back sounds in the medium range.For example, when adjusting the HPF, frequencies that are lowerthan the specified frequency are progressively dampened, ratherthan simply not being played back at all.The "slope" adjustment function is the function that is used to adjustthese dampening characteristics.The slope characteristics of a filter are such that with larger slopevalues (for example 12 dB/oct), the slope becomes steeper, and sothe amount of sound mixing in with neighboring bands becomesless so that only the target band is played back. However, it alsocauses the merging of sound between speakers to become poorerand can result in greater distortion.-3dB20HzBass range Medium range Treble range20kHzfc1(LPF) fc2(HPF) fc3(LPF) fc4(HPF)fc*: Cutoff frequency
