I have a 2014 Focus with the 6 speaker Sync system. As you all know the factory head unit allows you to adjust bass, mid, and treble. Does anyone know what frequency range each setting adjusts? I'm asking, because I'm going to add a small sub/amp combo to fill in the missing lows. Knowing the frequency range of the bass setting will help me dial in the sound. I plan to match my amp's low pass filter to the highest frequency the bass setting changes. This will allow me to use the bass setting as a fine tune "volume" for different types of music while limiting the amount of bass the factory speakers get. As an example: I could set the treble and mid both to +3 and tune the sub amp to sound good with the head unit's bass set to -2. I can then adjust the bass setting from -5 to 0 for fine tuning ability, but the factory speakers never have to handle more than a "0" bass setting. I hope I'm making sense.