The electronic crossover is used to drive individual loudspeakers for separate portions of the audio frequency spectrum. A two way crossover is used for bass and high frequency speakers. A three way crossover is used when driving bass, midrange and high frequency speaker. The signal from the preamp is passed to the electronic crossover network. The outputs of the crossover network are then connected to the power amplifiers for the individual loudspeakers. A typical configuration like this might have the crossover frequency set at 300 to 1000 Hz, depending on the type of loudspeakers used.  When used with subwoofers as low frequency speakers, the typical crossover frequency is around 100 Hz. The range is 50 to 150 Hz for most subwoofers. When the crossover frequency is below 100 Hz there usually is no stereo information present from the sound of the subwoofer, and a common subwoofer can be used. The sum switch on the crossover front panel causes the outputs of both low pass channel to be summed together. Both outputs will have the same summed signal on them, and either one can thus be used to drive he common subwoofer. The advantage of a common subwoofer is more than just cost. Because there is only one subwoofer present, often a larger unit can be chosen, with an extended bass range.

It is also possible to drive more than two speakers per channel. A three-way crossover would be used to drive a system with woofers, midranges and tweeters.

At frequencies below the crossover frequency the signal will go to the low-pass outputs. At frequencies above the crossover frequency the signal will go to the high-pass outputs. There is a region around the crossover point where the signal will come out of both the high pass output and the low pass output. For the crossover networks with a slope of 24 dB/octave (XM6, XM9 and XM26) the width of this region is about 1/2 octave. For the XM16, with a slope of 48 dB/octave, the width of this region is halved to 1/4 octave.
Figure 2 shows the frequency response of the 24 dB/octave crossover networks (XM6, XM9 and XM26). The figure is drawn for a crossover frequency of 100 Hz. For other crossover frequencies the same figure applies, with the frequency scale scaled. Note that both the high-pass response and the low-pass response are down exactly 6 dB at the crossover point of 100 Hz. This means that at this frequency the amplitude is exactly half. Adding the high-pass and low-pass together sum to unity. As a matter of fact the sum of the high-pass and the low-pass response is unity for all frequencies. This is why the filter is called a “constant voltage” network. It is also called a Linkwitz-Riley network.

The frequency response of the phase of the 24 dB/octave network is shown in figure 3. The frequency response of the phase is the same for the high-pass and the low-pass outputs. Note that at the crossover point the phase shift is exactly 180 degrees.
The choice of the crossover point is a difficult one, and often some trial and error is needed for achieving best results. With the 24 dB/octave crossover networks a good rule of thumb is to set the crossover point at least one-half to one octave away from the cutoff frequency of the speaker. Thus a satellite with a cutoff frequency of 50 Hz at the low and that is used with a subwoofer requires a crossover frequency of 75 to 100 Hz. The subwoofer should then also have a range extending half to one octave above the crossover frequency. In this case, if 100 Hz was chosen, the subwoofer should have a range of at least 200 Hz.

The level controls on the front of the cabinet are used to set the volume of each loudspeaker for a proper match. There are several ways to adjust these controls. A good way to do this is to start out by setting all controls in the center (12 o’clock) position. Listen to some music and adjust the controls for proper volume from each speaker.
If a frequency generator is available, hook the generator up to the input of the crossover. Sweep the frequency from way below the crossover point to way above the crossover point. When the frequency crosses the crossover point the sound should shift from one speaker to the other, but the volume should remain the same.
A third way is to use a pink noise generator and a spectrum analyzer with a good microphone. Adjust the level controls for a flat response across the crossover point.
Sometimes the methods that use instruments result in settings that are not quite pleasing. If that is the case try to adjust the controls until the sound is best. After all, it is the final sound that is important.

The damping control allows adjusting the frequency response at the crossover point. The damping control has maximum effect near the crossover frequency, and almost no effect far from the crossover frequency. Figure 4 shows the frequency response for the maximum and minimum settings. This control is only available on the XM6 and the XM9. The damping control adjusts both high pass and low pass simultaneously. This control is useful for fine-tuning the room frequency response. Sometimes it happens that at the crossover point there is a small peak or dip in the frequency response. This is caused by the fact that at this frequency the sound is produces by both high and low speakers simultaneously. It is often very hard to hear this dip, but it can easily be seen if a frequency spectrum analyzer is used.