Not delving too deep into electronic theory... The white ceramic block is a resistor. The capacitors and inductors are reactive to alternating voltage/current. The resistor is resistive to voltage. Reactive inductors / capacitors resist AC nonlinearly. I.E. whereas a resistor resists voltages equally no matter what the frequency, a reactive element (capictor, inductor) resists altenating current at selective frequencies based on it's value, and how it's used in a circuit. Combinations of reactive and resistive elements in circuits can allow certain frequencies to pass through to the speaker, while blocking others. This allows each driver to function within it's chosen bandwith, and integrate with the other drivers in the speaker system.

Specifics:

A Resistor in series is linearly resistive to DC and AC

A capacitor in series is an open circuit to DC, and reactive to low frequency AC.

An Inductor in series is conductive to DC, but reactive to high frequency AC

Within your ProAc's,they are all critical components. Each as critical as the next.

Specifics:

A Resistor in series is linearly resistive to DC and AC

A capacitor in series is an open circuit to DC, and reactive to low frequency AC.

An Inductor in series is conductive to DC, but reactive to high frequency AC

Within your ProAc's,they are all critical components. Each as critical as the next.