The Simplest Method of Non-open Space Phase Alignment

- Aug 20, 2018-

Everyone has a common understanding that in the open space, the phase of the speakers in the entire audio system is very important. One of the most important aspects of audio work at open-air music festivals is phase alignment.

So, do you need to align the phase in a simple system with a full-range low frequency in a small room? We all know that the relative phase of the low frequencies helps us determine the position of the low frequency sound source in the open space. But in the room, we lose our ability to judge because the reflection of low-frequency sound waves at the boundary of the room can cause chaotic sound waves.

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We couldn't detect the position of the subwoofer in the room, so the relative phase between the ultra-low frequency and the satellite speakers didn't seem so important.

However, we can also improve the sound field effect in some ways. The most important point is to start with their overlapping frequencies. These two systems usually overlap around 80-100 Hz. In the entire “intersection”, the full-range and subwoofer reproduce the same signal at the same time, and you can hear the sound from both full-range and subwoofer at the same time. Therefore, these signals must arrive in synchronization with each other so that they can be combined in an optimal manner rather than (partially) cancel each other out. If the latter occurs, the amplitude of the superimposed region will be greatly reduced, and the sound field effect will naturally deteriorate.

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Fortunately, this phase alignment is a very simple adjustment. All you need is to play the sine wave tones at the appropriate superimposed frequency (usually 80Hz) - so both full-range and subwoofers can reproduce the same signal. In this case, the subwoofer phase can be adjusted to find the loudest perceived output at the listening position. Some ultra-low frequencies provide continuous phase adjustment, while others offer switching options (0/180 degrees or 0/90/180/270 degrees). This is acceptable because the wavelengths involved are very long and do not require precise phase alignment.

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When the signals from the full-range and subwoofer are in phase with each other, the entire system emits the loudest output. Once the phase of the subwoofer is optimized, its level can be adjusted to seamlessly blend with the full range of speakers for optimal low frequency expansion.

 

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