Why add a subwoofer? Is it true that the bigger the subwoofer, the better? What should I do if the low frequency is mushy? How to adjust the subwoofer phase? For practical purposes, the author will not talk too much about theoretical and technical issues, but will directly interpret the problems that friends have doubts or encountered

▌In order to restore realistic multi-channel sound, subwoofers are indispensable

Whether it is the early DVD built-in Dolby Digital, dts, or the current Dolby Atmos (Dolby Atmos), Dolby True HD, DTS:X, DTS HD audio encoding, there are independent subwoofer channels, that is to say, under these formal multi-channel audio encoding specifications, it must be matched with one or more active subwoofers in order to show the middle and low frequency segments that should be in the audio and video software.

▌Don't judge the quality of the subwoofer by the size of the subwoofer

Many users believe that the size of the subwoofer must be as large as possible. In fact, this problem involves factors such as the driving power of the subwoofer itself, the type of the cabinet, the efficiency and instantaneous performance of the unit. Although a large cell can push the air over a larger area to produce more low frequencies, a large cell has a much heavier cone weight than a small cell, and in order to push it out of a stronger low frequencies, the amplifier circuit must first have a higher output power.

In addition, the instantaneous performance of large-size monomers is often not as fast as that of small-diameter monomers, so the sense of velocity during low-frequency transmission is often not fast enough compared with small-caliber monomers, and even the phenomenon of sound "tailing" will occur. As a result, subwoofers with large monoliths tend to provide more low-frequency content, and they are not as light and agile as small-bore monomers in terms of speed

▌The left and right channel woofers are powerful, do you still need to add a subwoofer?

The size of the speaker alone in an AV system can determine whether the mid-bass range (especially the low-frequency part) of the entire package is sufficient, because most regular multichannel systems will hand over the frequency band of 80Hz or below 90Hz in the response band to the subwoofer. Of course, if you don't have a subwoofer, you can also set the front left and right channels to the full range from the AV amplifier menu.

▌Although the bass has no direction, the subwoofer is phase-oriented

Phase is a measure of the change in the waveform of a narrative signal, usually in angles. When a complete wave pattern goes from the peak to the trough and back to the origin, the positive and negative sine waves formed are 360 degrees in total, that is, when the wave pattern is halfway through the 180-degree phase, it is exactly 0 degrees and 360 degrees to form an inverting wave pattern. To put it simply, in the placement adjustment of the subwoofer, when the subwoofer and the left and right channel speakers are both sounding in the same direction, the sound phase of the two should be close to the same phase.

▌ About adjusting the crossover point of the subwoofer

Active subwoofers are also typically equipped with crossover point adjustment. Due to the built-in crossover adjustment on the subwoofer, it is basically an adjustable LPF (Low Pass Filter) filter that allows signals below a fixed frequency band to pass through, which means that if the knob is set to 80Hz, the LPF will let the input signal below 80Hz pass through, and the frequency band above 80Hz will be filtered.

After figuring out the crossover point of the subwoofer, when we set the crossover point of the subwoofer, we can use the low-frequency extension of the speaker as a reference for adjusting the subwoofer crossover point. For example, the low-frequency response of a pair of speakers is marked at 60Hz, and the subwoofer crossover point can be set to about 70Hz when the speakers are removed, and the subwoofer crossover point can be set to about 70Hz.

For example, many AV amplifiers are set to the front left and right channels in the front of the HPF in the frequency band above 80Hz, and the signal below 80Hz will be forwarded to the signal output terminal connected to the subwoofer, so we can set the subwoofer crossover point at 80Hz. This not only makes the amplification circuit inside the subwoofer work more easily, but also cleans the low-frequency tone of the subwoofer

▌ I can't feel the shock effect of the subwoofer, and even the low frequency is muddled

When it comes to adjusting the settings of the subwoofer, it may be much more difficult than the AV amplifier. The AV amplifier can be set up according to the manual, especially since many new-generation models can help you adjust the system settings fairly accurately in a matter of minutes by simply plugging in the microphone and pressing the button. But the adjustment of the subwoofer can't make the user so lazy. In addition to several more advanced subwoofer models on the market equipped with detection microphones, most subwoofers still rely on the user to constantly adjust the position, phase, volume and crossover point to get a natural and unobtrusive low frequency effect.