Room Analyzer Part 3 :"Cary Audio、JL Audio你兩可玩得我透了"

用了xtz 的Room Analyzer II Pro約三星期，和Cary Audio C11a及JL Audio F110搏鬥了超過二十個鐘，只可以說:"Cary Audio 你可玩得我透了"，一直不明白為可音壓在120hz左右會下跌得這樣厲害，到最後:-

Front crossover: 80hz，Sub-woofer crossover: Full， sub-woofer gain: 12 o'clock， Phase: 0 degree，Polarity: negative，elf: - 8dB，Distance: 10'

Front crossover: 80hz，Sub-woofer crossover: Full， sub-woofer gain: 12 o'clock，sub-woofer level: - 5dB， Phase: 0 degree，Polarity: negative，elf: - 8dB，Distance: 10'

Front crossover: 80hz，Sub-woofer crossover: Full， sub-woofer gain: 11.5 o'clock，Phase: 0 degree，Polarity: negative，elf: - 8dB，Distance: 10'

Front crossover: 80hz，Sub-woofer crossover: Full， sub-woofer gain: 11 o'clock，Phase: 0 degree，Polarity: negative，elf: - 8dB，Distance: 10'

根據Cary Audio C11a的usual manual在crossover一項有這樣的指示:

[SET CROSSOVER POINTS

The LPF/HPF (Low Pass Filter/High Pass Filter) Crossover menus are used to independently set 

the internal High Pass filter of the Cinema 11a each of the speakers. 

Setting the Speaker Crossover Points 

In the Cinema 11a, the Crossover Points can be selected in 10Hz increments within a 40Hz to 

150Hz range, or each speaker can be set to receive full range signal. Select the crossover point 

closest to the low-frequency rating of the associated speaker. For instance, set to FRONT L/R 

parameter to the crossover point closest to the low-frequency rating of the front speaker. 

Select the subwoofer crossover point equal to the lowest crossover point of the other speakers. 

In general, low frequencies will be redirected from the speakers with the highest crossover points 

to the speakers with the lowest crossover points. Low-frequency signals lower than the lowest 

crossover point will be redirected to the subwoofer. ]

根據以上示指，假設最底的crossover是Front Speakers，而Front Speakers的crossover point為60hz，那sub-woofer的crossover亦應設定為60hz。不過最尾一句又好像是說到最後低過最低分頻點的低頻會被送到sub-woofer。

十分奇怪的是如在Cary Audio將Sub-woofer的crossover設定在"Full"以外其他所有crossover 組合，包括Front crossover: 40hz、50hz、60hz、70hz、80hz，Sub-woofer crossover: 40hz、50hz、70hz、80hz、100hz、120hz、150hz等在120hz會出現衰減情況，奇怪的是如sub-woofer的crossover設在80hz甚至是50hz理應不會涉及120hz的。

值得注意的是在做Room Analyzer時用的是2.0訊號以Analog入Cary Audio C11a的7.1 Analog input，之後經Cary Audio C11a的DSP做Bass Management的工作，所以如果Cary Audio C11a的Sub-woofer crossover是類似LPF of LFE的話，即是Sub-woofer crossover只會是對.1(LFE) channel有影響，Sub-woofer crossover point的設定應該不會對Room Analyzer有所反應。但事實上Cary Audio C11a的Bass Management有點不同。

如將sub-woofer的crossover設在Full的話120hz是不會像其他的設定有所衰減。之前在實際播放電影時亦發現將Sub-woofer crossover設為120hz的話低頻明顯比80hz或60hz時豐滿。以下為其他crossover設定時的curve:-

crossover: 40/40

 crossover: 50/50

 crossover: 60/60

 crossover: 70/70

 crossover: 80/80

 crossover: 80/100

 crossover: 80/120

 crossover: 80/150

看似是Cary Audio C11a的問題，但試將sub-woofer的crossover設為Full而在JL Audio的crossover filter作過濾，但出來的curve又怎樣呢?

crossover: 80/Full JL filer: 0 -12dB

 crossover: 80/Full，JL filter: 80 -12dB

 crossover: 80/Full， JL filter: 100 -12B

 crossover: 80/Full， JL filter: 130 -12B

先用這個設定Front crossover: 80hz，Sub-woofer crossover: Full， sub-woofer gain: 12 o'clock， Phase: 0 degree，Polarity: negative，elf: - 8dB，Distance: 10' JL filter:off 。

之後以十分細的音量(因為已是零晨一時)將所以Power Amplifier 關掉只剩sub-woofer，但當用耳仔貼近sub-woofer是會聽到微弱的人聲，不明白為可LFE會有人聲，如果是由Front Speaker傳來的，在80hz crossover的設定下人聲亦不應傳到sub-woofer，今晚會實際用電影試一下效果如何。

老實說，用了Room Analyzer後才知道Cary Audio C11a的crossover setting是如此特別。