1st, 2nd and 3rd Order (12dB) Series Crossover

Almost all loudspeakers hold electric crossovers, as almost all loudspeakers hold more than one speaker driver; hence the need for a means of splitting up the audio bandwidth and sending each driver its portion of the bandwidth. And almost all loudspeaker crossovers are of the parallel-design type, where both drivers share common input and ground connections,

An alternative crossover type is the series type, where each driver sees its own separate input and ground connections.
If you look through a woofer's data-sheet specifications, you will find an entry labeled "Le" that stands for the woofer's own inductance. As long as this value is less than the crossover specified inductor value, we can subtract the woofer's Le from the crossover inductor value. If the woofer's value is greater, then a lower crossover frequency must be used.

2 Way 1st Order Linkwitz-Riley 2 Way 2nd Order Linkwitz-Riley 2 Way 3nd Order Linkwitz-Riley 3 Way 2nd Order Linkwitz-Riley