The third question: low frequency management/subwoofer crossover
With a subwoofer, crossover is inevitably involved. If it is a system with only one subwoofer, usually if you want more than one emperor position, the crossover point adjustment may be more difficult than the multi-subwoofer system, or the phase adjustment requires a certain compromise, considering more positions.
The ultimate difficulty of this problem is reflected in the car audio system.
Usually a brand car speaker system has one (or two) subwoofer (Subwoofer) and four woofers (Doorwoofer). Of course, audiophiles call this mid-bass, but in fact, car manufacturers usually call this subwoofer. But the name is not important. Although there are many modes for the car audio system, if it is the all-passenger mode, the bass performance of the four positions in the car needs to be better. But usually things are not that simple.
The subwoofer can be adjusted to match the superimposed phase of multiple woofers in the driving position, but at this time, the superimposed phase interference of the subwoofer and multiple units in the rear row may cause the rear bass effect to be poor.
At this time, you can adjust the phases of different door woofers to make the rear bass perform better, but interference between different door woofers may cause poor front bass performance.
A certain amount of interference can be balanced by assigning different woofer gain ratios, but it may cause the bass to reach the limiter in advance and cause dynamic range problems.
However, adjusting the phase of the door woofer itself may cause the phase of the higher frequency band to be involved, resulting in sound field and tone problems. Etc., etc.
The summary in one sentence is-to move the whole body.
In short, this is a process of selection and reciprocating debugging. Of course, even a simple bass crossover system is sometimes not always the best solution to the phase. Sometimes you need to consider the actual situation and the characteristics of the speakers and the subwoofer itself to determine the crossover point.
The difference between the phase of the multi-channel system and the stereo system is not actually the difference of the phase itself, but is caused by the difference between the direct interaction of multiple speakers and the stereo playback system, or it can be explained as the difference between an asymmetric system and a symmetric system. the difference.