Passive Crossover Basics

There are two categories of Crossovers – Passive and Active. The main difference is that Passive Crossovers filter audio signals without power, and there are usually no adjustments that can be made. Active crossovers are powered and need an experienced technician to make the required adjustments to “Calibrate the System” in order to get optimal performance from the loudspeakers.

Passive Crossovers

Basically “Plug and Play” and found in most 2-way or 3-Way “Passive” speaker cabinets / monitors.
Fewer Amplifiers are needed – Example: One amplifier channel can power one passive speaker cabinet.
Not 100% efficient as components can fail due to heat buildup, clipping, and overdriving the speaker.

2-Way Passive Speaker Handout!

Parts of a Passive Crossover – What do they do?

Passive crossovers consist of LCR components. The three main components are Inductors, Capacitors, and Resistors. This combination of components is referred to as LCR components. These LCR components do not need a power supply to operate. They are basically used for “separating” the audio signal so the desired frequencies can feed the correct speaker component.

L = Inductor – Inductors pass Low Frequencies and filter out High Frequencies. Inductors are also referred to as Low Pass Filters, and Coils.
C = Capacitor – Capacitors pass High Frequencies and filter out Low Frequencies.
R = Resistor – Resistors are basically used for attenuation. Extra power gets shunted (diverted) through the resistor, and helps with maintaining a constant “load” for the amplifier.
Protection Components – Over-Power protection lamps are basically a type of “fuse” that helps to protect the tweeters. They do not affect the sound quality. There are other types of Tweeter protection “fuses” used with passive crossovers as well (not shown).

The image (below) shows a typical passive crossover for a 2-way full-range “Passive” speaker cabinet. One amplifier input is “divided” through the crossover network circuit, then distributed to the correct speaker components through the High-Frequency and Low-Frequency Outputs.