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

The configuration of modern sound amplifierequipment, creating surround sound, involves the functional separation of channels. This audio system includes front and rear speakers, center channel and subwoofer.

The latter serves to create additionalsound 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 rather intensively.

As a rule, subwoofers are designed according toactive principle, that is, have their own built-in amplifier, power supply and adjustment. Controls and settings include two main knobs: "Level" (Level) and "Cutoff Frequency" (Crossover Frequency). The purpose of the level knob is quite understandable, it is the regulation of the intensity of the sound signal. But why do we need the second setting, it is not clear to everyone.

Unlike broadband loudspeakers,The subwoofer has a limited upper frequency range. In turn, the bass is conventionally divided into deep - up to 40 Hz, medium - up to 80 Hz, and high - up to 160 Hz. The depth of the achievable acoustic effect depends on which cut-off frequency is set. In some cases, participating in the high bass spectrum creates a softer sound, for example, when listening to music or watching movies that are not loaded with special effects. If a more severe impact on the viewer's nervous system is required, for example, when seeing collapsing buildings or exploding planets, then the cut-off frequency of the subwoofer can be shifted closer to the infrared range.

Технически реализация ограничения верхней частоты - the task is simple. It is known from the physics course that capacitors have a filtering property with respect to low frequencies, and inductances - to high ones. Thus, the simplest LC filter can effectively allocate the desired part of the range, while reducing the signal level of the unwanted spectrum. In order to “keep out” the high and medium frequencies at the subwoofer input, it is enough to connect a small capacitor across the input terminals in a few picofarads. But such a primitive filter will give a too smooth decrease in the amplitude-frequency characteristic, therefore, in practice, their design is somewhat more complicated.

In addition, the cutoff frequency is provided andfiltering the output of a powerful loudspeaker. To do this, inside the case next to the speaker is another card with capacitors and inductors.

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

Correct setting of the subwoofer in relation toother acoustic components of a home theater system is a matter that requires patience and care. A good regulation is considered such that the basses emitted by the front and rear speakers are complemented by infra-low frequencies broadcast by him, and 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, ensuring the correct and consistent sound of the entire system.