From what I understand(I don't build speakers), when manufactures build speakers they will match speakers of different sensitivity ratings, the cross-over will in itself use up a given amount of the amps output( this will vary with each cross-over and each speaker)the mid/low driver may have a sensitivity of x amount and the tweeter x amount. These variables are usually not the same (matched) but different. A average of the two is calculated somehow and the crossover is then calculated in also and the final resistance is measured and a givin # is the result the outcome. What I am trying to find out is the seperate values of the individual drivers.