volume adjustment or crossover point adjustment is easy to understand, what is phase adjustment or phase switching?

The so-called phase adjustment is continuous or segmental adjustment from 0-270 degrees, and phase switching is only two phase switching of 0 degrees or 180 degrees. Why do you need phase adjustment? Simply put, when the low frequency emitted by the subwoofer is mixed with the low frequency emitted by other speakers, if the phases of the two are the same or close, the total low frequency sense is the sum of the two. Conversely, if the phases of the two are opposite or close to each other, the total low frequency sense will be subtracted. In theory, when the subwoofer is placed on the same horizontal line as the front, middle or two-channel speakers, the low-frequency phase should be the same or close to the front channel or left and right channels. The problem is that many people can't place the subwoofer on the same horizontal line between the left and right speakers for a variety of reasons, but at a corner or side, where the subwoofer emits sound and other phases. The speakers will be different, so it is best to have a phase adjustment. Generally, the phase adjustment on the subwoofer is divided into two types. The simpler one is the 0-degree and 180-degree second-speed switching. The subwoofer is preferably placed between the corner or the front channel or the left and right speakers, even if it cannot be placed. Also try to be as close as possible to the front channel or left and right speakers. Another more precise adjustment is the 0-270 degree stepless or segmented adjustment. This phase adjustment has a higher selectivity and the position of the subwoofer can be more flexible. How do you determine if the adjusted phase is correct? It's very simple, you just have to listen with your ears, and choose the one with the most low-frequency sense. Of course, you'd better have a pink noise or a variety of frequency test strips, broadcast the frequency range of 20Hz-150Hz on the test piece, or choose a single frequency (for example, 60Hz) to listen, so you can hear the most abundant low-frequency sense. .