The Design of Active Crossovers, 2nd Edition

Chapter 6

Subtractive Crossovers

Subtractive Crossovers

What you might call the standard crossover architecture has a lowpass filter to generate the LF signal for the bass drive unit, and a corresponding highpass filter to create the HF signal for the tweeter/midrange driver. (Obviously this only describes a 2-way crossover, and a 3-way crossover has more filters.) That is not, however, the only way to do it, and one of the alternatives is the subtractive crossover. In this you just have one filter, say the lowpass, which gives the LF signal, and you make the HF signal by subtracting the LF signal from the original input, so that HF = 1 − LF. This process is illustrated in Figure 6.1, which shows a 1st-order subtractive crossover. Higher-order ...