I just had a reputable shop install my 15inch subwoofer with amp tapped into the stock system of my W202 Kompressor sedan.

Did a good job....but being a 15 inch subwoofer its meant for really low frequencies and the rear shelf non bose speakers in my car are somehow set to a special frequency which the sub doesnt match to....meaning in certain songs I play, it sounds like there is no sub...but if there is a low "boom" part it kicks in.

Can this be solved swapping to a 12 inch sub or 2 10 inch?
They pick up more higher bass.

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