What is the cutoff frequency of the subwoofer and how to properly adjust it

The configuration of modern sound amplifying equipment that creates ambient sound, assumes functional separation of channels. This audio system includes front and rear speakers, a center channel and a subwoofer.

The latter serves to create additional sound effects in the lower frequency range from 20 to 180 Hertz. Basically, this additional device is used when viewing video programs and films, which contain scenes of explosions, launches of space rockets and similar situations, with the sounding of which you need to sufficiently shake the air.

As a rule, subwoofers are designed on an active principle, that is, they have their own built-in amplifier, power supply and adjustments. Controls and settings include two basic knobs: "Level" and "Crossover Frequency". The purpose of the level handle is quite understandable, this is the regulation of the intensity of the sound signal. But why do you need a second setting, it's not clear to everyone.

Unlike broadband loudspeakers, the subwoofer has a limited frequency range at the top end . In turn, the basses are conventionally divided into deep ones - up to 40 Hz, medium ones - up to 80 Hz, and high ones - up to 160 Hz. The depth of the acoustical effect depends on how the cutoff frequency is set. In some cases, participation in the spectrum of high bass creates a softer sound, for example, when listening to music or watching movies that are not loaded with special effects. If you require a more severe impact on the nervous system of the viewer, for example, when looking at crumbling buildings or exploding planets, the cutoff frequency of the subwoofer can be shifted closer to the infra-band.

Technically, the implementation of the upper frequency limit is not an easy task. From the physics course it is known that capacitances have a filtering property with respect to low frequencies, and inductance - to high. Thus, the simplest LC-filter can efficiently isolate the desired portion of the band, while reducing the signal level of the unwanted spectrum. To prevent high and medium frequencies from entering the subwoofer, it is enough to include a small capacitor in parallel to the input terminals - several picofarads. But such a primitive filter will give a too smooth decrease in the amplitude-frequency response, so in practice their design is somewhat more complicated.

In addition, the cutoff frequency is also provided by filtering the output signal, which goes to the powerful loudspeaker. For this purpose, another board with capacitors and inductances is located in the housing next to the speaker.

The cutoff frequency of LPF (low-pass filters) should ideally be regulated, although in low-cost systems such a function may not be.

Properly adjusting the subwoofer in relation to other acoustic components of the home theater system is a matter requiring patience and thoroughness. It is good to have such a regulation, in which the basses radiated by the front and rear speakers are complemented by the infralow frequencies broadcast by them, and not "arguing" among themselves, who is stronger. The principle "the louder the better" does not work here.

Thus, the cutoff frequency is an important setting that ensures the correct and consistent sound of the entire system.