Crossover PCB designed for a range of 2 way passive crossovers with attenuation on the high-pass section.
Dimensions: 105 x 150mm
For standard symmetrical butterworth filters, the component values will be the same for both high pass and low pass sections.
L1 is the low pass inductor, and will usually be physically larger as it will handle more power than the high pass inductor. Often a ferrite or iron cored inductor is used for low pass to keep the inductor smaller, and the DC resistance lower. Ferrite cores will introduce some distortion, but this is generally deemed acceptable to minimise losses and keep inductor cost/size down to a minimum.
L2 is the high pass inductor, and in higher power / high quality applications it is preferable to use an air cored inductor to reduce distortion.
C1 and C2 are for the low pass capacitor(s) - two spaces are provided so that capacitors can be arranged in parallel to achieve the desired value. e.g. for 4.4uF it would be preferable to use 2 x 2.2uF capacitors instead of 1 x 4.7uF capacitor.
PTC1 is a location for a poly switch. If there is a power spike, the polyswitch will close, passing the signal through R1 to attenuate and protect the HF Device.
R2 and C3 are in parallel- R2 is an attenuation resistor for the HF output,. Putting a Capacitor (C3) in parallel with R2 allows for a HF lift to create a CD Horn EQ.
If you are not using PTC1 for protection, you can use a combination of resistors for R1 and R2 to create the desired attenuation for the HF. Please note though, C3 is in parallel with R2 only, so the HF boost from C3 is controlled by the attenuation from R2.
If you are not using R1/R2 you will need to put in link wires in appropriate places for the signal to reach the High Pass circuit.
A link wire is also required on the output of the HF circuit, without the link in place, it is possible to do third order high pass with some combinations of capacitor, replacing the output link with the appropriate capacitor.
C4 and C5 are for the high pass capacitor(s) - two spaces are provided for arranging capacitors in parallel.
Need some help calculating values? Why not try our crossover calculator: Crossover Calculator
Select the filter type, frequency and driver impedances and then click the upper 'CALC' button to get the values you need for your crossover. The results will give a value for C1 (created using C1, C2 and C3 on the board) and C2 (created using C4 and C5 on the board). L1 and L2 will be as designated on the PCB.
The PCB has the high pass and low pass marked with standard + and - connections.
It is very common to connect the Tweeter (High Pass) in reverse phase on a butterworth crossover as this will often give a more uniform response across the crossover point. It is worth trying both normal phase and reverse phase to see which works best in your system.