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Two-Element Crossovers

Author: N.H. Crowhurst

This arrangement works by progressive current division that accentuates the separation. The first division is by series components, connected to the output in parallel. Then each unit has a further component in parallel with it to bypass the unwanted frequencies.

More complicated crossover using two capacitors and two inductors

The low-frequency loudspeaker is bypassed at higher frequencies by the capacitor connected across it, then the inductor in series with it further blocks higher frequency voltage. However, the action is a little more complicated than this. The inductance and capacitance interact, rather like a tuned circuit in a radio, with the result that the energy is delivered to the low-frequency unit more efficiently at frequencies near to cutoff (the crossover point). This can be shown by plotting the frequency responses and comparing them with the simple circuits.

Notice that below the crossover point the low-frequency unit is fed more efficiently with the improved network, and that the response falls off more rapidly above crossover, due to the double action. The same thing happens with the feed to the high-frequency unit: the inductor in parallel with it bypasses the low-frequency currents, and the capacitor in series blocks the low-frequency voltage. The interaction again works like a tuned circuit to improve the efficiency just above crossover point, and to make the response fall off more rapidly below it. The first pair of components divide current, as in the simple current-dividing network, and the component connected in parallel with each unit accentuates the action by redividing the current.

A similar development can be made, using progressive voltage division. Here the voltage-blocking components are in series with each unit, then the current bypass components are in series across the amplifier output to cause voltage redivision. The values of the components are different from those in the other circuit, but the results are the same.

Another arrangement using two capacitors and two inductors

Last Update: 2010-11-03