Why Linkwitz-transformers?

Linkwitz-transformation is an active filter technique to change the bandwidth of a driver. With Linkwitz-transformation you can change the cutoff frequency and the quality factor (Q) of the low and high end of a driver.

Widening the bandwidth requires more power. Making the bandwidth smaller makes the system more efficient.

Linkwitz-transformations are used to make the bandwidth of each driver complementary to each other. So, in stead of cutting off the response of drivers the responses are shaped.

The Linkwitz-transformations are used to compensate the extra peak around resonance with current-drive. This an electronic way to dampen the resonance.

The Linkwitz-transformations are also used to create coherent or synchronous Duelund type crossovers, which makes the drivers operate at the exactly the same phase through the whole bandwidth.

And the Linkwitz-transformations are used to extend the frequency range at the low end and to adjust it at the top end. So, it is not the  resonance frequency of the woofer which determines the lowest frequency, but the maximum possible displacement of the woofer. The bigger, the lower.