Yeah, the shape is obviously more complicated than just a rolloff, because then it swings back up again--this is due to the unique interactions between the cables and the specific pickup I was using. Other pickups might have somewhat different patterns. But overall, yes you are seeing rolloff of the highs, and you are seeing more rolloff as the total capacitance of the cable goes higher. In the graphic, total capacitance varies from one cable to the next due to their design--but when you compare a short cable with a long one of the same make & model, you will see the exact same change in amount of highs rolled off (total capacitance of a 30' cable is double that of a 15' cable of the same design).