Simple Passive Crossover Network Circuit for Loudspeakers

Consider a conductor organizing the instruments in an orchestra.

In a speaker system a passive crossover network functions similarly to that conductor but for sound.

Like small speakers regular speakers are made up of several pieces each of which is designed to handle a particular tone.

Woofers provide deep booming sounds, tweeters produce high squeaky sound and at times middle drivers produce in between tones.

A smart switch is similar to the crossover network.

After mixing all the tones into one it divides the music signal into various components.

After that the tweeter receives the high tones the woofer receives the low tones and the midrange driver receives the mid tones.

Circuit Working:

Parts List:

You can see from the above figure that the 3.3uF capacitor and the inductor coil are connected to the positive a terminal from the input.

The capacitor is connected to the tweeters negative terminal while the inductor is connected to the bass units positive terminal.

The negative input is directly connected to the negative connectors of both drive units.

An optional 2.2 ohm 7 watt resistor is either installed if you want to boost the tweeters attenuation.

One may obtain an extra 0.8 dB attenuation by just unplugging the 1.5 ohm resistor and putting in the 2.2 ohm resistor.

This basic passive crossover network has an octave of 6 dB and is designed to function at 4 kHz.

Along with a resistor and capacitor in the tweeter part it also has an inductor choke in the lower frequency range to help with bass and mid roll off.

While the capacitor protects the tweeter the resistor reduces the tweeter and lowers its output by 1.4 dB solving a minor mismatch between the two sections.

The crossover uses premium air cored inductors and polyester capacitors to improve the final sound quality.

Using a few parts reduces the possibility of long term system inefficiencies which is a significant benefit of simple crossover networks.

With a high efficiency rating of 88.6 dB SPL at 1 meter/1 watt the final system surpasses previous less efficient systems in terms of output per watt.

Formula:

Below formula is used as a low frequency filter in a passive crossover network circuit.

The following formula are used to get the correct capacitance:

C = 1 / (2 πfXc)

where,

• C is the capacitors capacitance expressed in farads F.
• π (pi) is a constant in mathematics and its value is around 3.14159.
• f shows the AC signals frequency in hertz Hz.
• Xc is an ohm Ω representation of the capacitive reactance.

The formula basically instructs us on how to calculate the capacitive reactance using the AC signal frequency and capacitance.

Note:

This formula helps with better understanding and how capacitors behave in AC circuits.

By knowing the capacitors capacitance and frequency one can calculate the resistance (reactance) it gives to the current flow.

How to Build:

To build a Simple Passive Crossover Network Circuit for Loudspeakers follow the below steps:

Recognize the Diagram:

• Start by understanding the given circuit diagram
• Select the input, inductor coil, capacitor, bass unit and tweeters positive and negative connections.

Connect the Input:

• As shown in the diagram connect the positive input to the capacitor and the inductor coil.

Connect the bass unit:

• Connect the inductor coil to the bass units positive terminal.
• Make sure the tweeter and bass units negative pins point straight to the negative input.

Connect the Tweeter:

• Connect the tweeters negative terminal to the capacitor.
• A crossover point between the tweeter and bass units is generated by this set up.

Wiring and Soldering:

• To make sure the connections are secure use soldering equipment.
• To avoid any short circuit make sure the wiring is clean and properly insulated.

Testing:

• Once the crossover network is put together thoroughly test the system using speakers and an audio source that operate together.
• Make sure that every part is operating as it should and that the crossover is successfully sending frequencies to the right components.

Adjusting:

• Depending on ones tastes and unique features of the speakers adjust the resistor levels or crossover components as needed.

Conclusion:

By keeping each driver operating within its ideal frequency range a well designed passive crossover network reduces distortion and increases the loudspeaker systems overall sound quality.

Depending on the number of drivers and the required level of audio quality crossover networks can be both simple or complicated.

Understanding the individual driver specifications electrical components and the loudspeaker systems main objective is necessary for designing an efficient crossover network.

Reference:

Analog, Active Crossover Circuit for Two-Way Loudspeakers

Audio crossover