Modern surround sound amplification equipment is configured with functional channel separation. This audio system includes front and rear speakers, a center channel and a subwoofer.
The latter is used to create additional sound effects in the lower frequency range from 20 to 180 Hertz. Basically, this additional device is used when watching video programs and films that contain scenes of explosions, launches of space rockets and similar situations, when voicing which you need to shake the air quite intensively.
As a rule, subwoofers are designed according to the active principle, that is, they have their own built-in amplifier, power supply and adjustments. The controls and settings include two main knobs: “level” (Level) and “cutoff frequency” (Crossover Frequency). The purpose of the level knob is quite clear, it is the regulation of the intensity of the sound signal. But why the second setting is needed is not clear to everyone.
Unlike full-range loudspeakers, the subwoofer has a frequency range limited at the top edge. In myturn, the basses are conditionally divided into deep - up to 40 Hz, medium - up to 80 Hz, and high - up to 160 Hz. The depth of the achieved acoustic effect depends on what cutoff frequency is set. In some cases, participation in the high bass spectrum creates a softer sound, such as when listening to music or watching movies that are not laden with special effects. If a more severe effect on the nervous system of the viewer is required, for example, when seeing collapsing buildings or exploding planets, then the subwoofer cutoff frequency can be shifted closer to the infra range.
Technically, the implementation of the upper frequency limit is a simple task. From the course of physics it is known that capacitances have a filtering property in relation to low frequencies, and inductances - to high ones. Thus, the simplest LC filter can effectively select the desired part of the range, while reducing the signal level of the unwanted spectrum. In order to “keep out” high and medium frequencies at the input of the subwoofer, it is enough to connect a small capacitor in parallel with the input terminals - a few picofarads. But such a primitive filter will give too smooth a decrease in the amplitude-frequency characteristic, so in practice their design is somewhat more complicated.
In addition, the cutoff frequency is also provided by filtering the output signal going to a powerful loudspeaker. To do this, inside the case next to the speaker is another board with capacitors and inductances.
The cutoff frequency of the LPF (low-pass filters) should ideallyadjustable, although low cost systems may not have this feature.
Setting up the subwoofer correctly in relation to the other acoustic components in your home theater system is a matter of patience and care. Such regulation is considered good, in which the bass emitted by the front and rear speakers are complemented by infra-low frequencies transmitted by them, and do not “argue” among themselves who is stronger. The principle "the louder the better" does not work here.
Thus, the cutoff frequency is an important setting to ensure the correct and consistent sound of the entire system.
