Subwoofer Crossover
using frequency sweep 200Hz-20Hz L-C-R




 

 THX insists on a high level of quality in the products that we endorse. For a home theater system to carry the THX logo, the products must pass a stringent THX Certification process. Although in 5.1 sound systems there is a discrete channel for the low frequencies - LFE (subwoofer), low frequencies can still exist in the left, center, and right channels, depending on the soundtrack. Depending on how your receiver is set-up, these low frequencies will crossover into the subwoofer channel. Some systems may have problems in a seamless crossover from the Left-Center-Right channels to the subwoofer. As this may affect system set-up and adjustments, it is best to know how your system is performing.

A tone, which starts at 200Hz and transitions down to 20Hz, is generated in the left, center and right channels during this test. The purpose of the test is to alert you to any frequencies that might drop out or not be faithfully reproduced as your Left-Center-Right speakers crossover to the subwoofer. Listen for a drop in volume level during the transition. A high quality system will reproduce the tone sweep smoothly and without volume level fluctuations as the frequency decreases. Systems that appear to vary in audible levels may need further diagnosis. Although any problems maybe inherent in the system, it is important to know what your sound system is capable of reproducing. Faults may be due to a variety of reasons, but the best resource would be your local home theater salesperson. They may suggest a variety of options for you to try. Don't forget to check out the THX recommended list of home products!

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重低音衔接
使用200Hz-20Hz的左中右扫频信号

 

 


THX的产品认证都坚持高标准。THX家庭影院的5.1声道系统,虽然通常都设置有分离的超重低音声道,但混音时低音也可存在于其它声道。你可能设置这些信号转接到超重低音音箱回放。一些系统转接左中右信号到超重低音声道时会有问题。这样可能会影响到系统,最好找到你系统的最佳设置。

测试时左中右发出200Hz到20Hz的渐变音。如果在某一频率处,发出的声音音量明显降低,那就是合适的衔接频率位置。高质量的系统音调转变是平滑的,没有音量变化。如果系统的音量有变化,系统就需要调整。系统不能正确回放声音,可能是系统的内在缺陷。最好向家庭影院的经销商寻求建议。
 

 

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m17译自www.thx.com
2002/01

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