I designed a simple 2-way passive audio crossover, consisting of 2 power inductors and 2 capacitors. This makes for a second-order design or 12 dB/octave. This order is commonly used in passive crossovers as it offers a reasonable balance between complexity and response. Higher order audio filters are harder to design, because components interact with each other.

Supplies

Material:

-Custom PCB

-2 power inductors

-2 non polarized electrolytic or ceramic capacitors

-Solder

Tools:

-Reflow oven or a soldering iron (depends of your components choice)

Step 1: Schematics and Math

For the schematics design we need to calculate the component values. I used an online calculator for this task, with a crossover frequency of 4000 Hz. We could go lower on the crossover frequency but I want to better protect the tweeter from lower frequencies. After calculating the values I chose the nearest standard value. When choosing the power inductors you need to take in the account the maximum saturation current that can flow through the inductor.

Step 2: Custom PCB

I designed a custom PCB for the components I chose. The PCB features solder pads for both speakers and amplifier source. I aslo added mounting holes for later mounting in the speakers box.

Step 3: Component Soldering

The components are all surface mounted. To solder them I used indium solder paste and a reflow owen. I applied the solder paste to the PCB using a simple toothpick. The reflow owen must carfully follow the predifined solder paste temperature profile, which ensures good solder flow and connection.