Calculation & Test Result (Phase of Subwoofer)

bbsai

http://www.audioxpress.com/magsd ... ia/godmaire_pt4.pdf
留意 Page 3, Table 1
由於計算時考慮到不同既前置 low freq,
大家可以參考一吓!



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圖解 : This case setting for Subwoofer/Front Speaker        : 120Hz/120Hz

Existing Testing Equipments

Front Speaker (L/R)
Klipsch RB-61        frequency response 43Hz-23kHz +/-3dB

Prepare 80Hz signal
Download 80Hz mp3, change it format from mp3 to CD

Measurement Signal Level Equipment
Velodyne DD-10

Amp. setting
Subwoofer Cut-Off Frequency        :        80Hz
Front Speaker (L/R) Frequency        :        Full Band (My case 43Hz-20kHz)

Result

Phase                 Measurement Level (dB)
        (  0  )        69        (Subwoofer use "Mute" mode)
Nil  /  (+90 )        74.5
         (+180)        76
-90  / (+270)        78
          (  0  )        78
-105 / (+255)        79        (Table1 suggest my case value -105)

Conclusion

如可有效率地發揮subwoofer既低頻力量...
Phase : unknow (+0,+90,+180,+270)
Cut-Off Frequency : 80Hz
Front Speaker Low Frequency : 20/30/40/50/60/70/80Hz
只需要用 spl meter去量不同 phase 既 level (Source signal =80Hz), 最高 level既 phase 就係答案~~

Step1        :        Consider amp. setting
                for example:
                Subwoofer/Front Speaker        : 80Hz/80Hz
                Subwoofer/Front Speaker        : 80Hz/60Hz
                Subwoofer/Front Speaker        : 80Hz/Full Band

Step2        :        Find the best phase value
Step3        :        Tune subwoofer level
Step4        :        Tune subwoofer EQ.

before (Phase set "+0") :
為咗聽對白較大 volume....
低音量強行整出來...
有種隔隔不入的感覺...
有d位會打心口感....但無咁分明...好似到喉唔到肺...
用條普通平既線同條自己整既銀線分別係有...但要好细心留意...

now (Phase set "-105") :
不需要為聽對白去較大 volume.
低頻量多既地方會覺得自然咗~~
lee種係咪隔合既結果?!
聽開有 "non-打心口"既低頻段會無咗
但有新既底頻位出現....有時會有較大既打心口感...明顯既!
聽到用平線和銀線既分別明顯好多...

bbsai

Updated information~~

kfai

如果可以既話,用你既經驗,精簡用中文總結以上果５頁既report,同post76既兄弟一切分亨
可以嗎？小弟不材.勿見怪！tks!

chhanthony

有排睇

bbsai

4# ryanenen


ryanenen hing,
哈哈~~
lee 個 topic 比想像中深好鬼多~~~講真既!

我睇完有 dd 結論

1,(Table 1)
我哋可以知...唔同前置既 low freq. 會影響 subwoofer phase.
example
A speaker freq range from : 40Hz-20kHz
B speaker freq range from : 50Hz-20kHz
C speaker freq range from : 60Hz-20kHz
D speaker freq range from : 70Hz-20kHz
E speaker freq range from : 80Hz-20kHz (THX standard)

2,(Table 1)
當 subwoofer cutoff freq. 同 speaker low freq 一樣 (equal case)
個 phase 會係 " 0 " & " -180"

3,
圖中所見 cutoff freq. is 120 Hz
若果我哋用 spl meter,俾 120Hz 個 speaker 去量...
當正確 phase , 果一段 120 Hz level 會最高~~
反之....果 3 case 其中一個會最低...另外 2 個會一様...

bbsai

講漏咗...佢個圖測試時佢 subwoofer 無較大 +10 db ...佢係較平 level 先...

kfai

4# ryanenen


ryanenen hing,
哈哈~~
lee 個 topic 比想像中深好鬼多~~~講真既!

我睇完有 dd 結論

1,(Table 1)
我哋可以知...唔同前置既 low freq. 會影響 subwoofer phase.
example
A speaker freq ...
bbsai 發表於 2009-8-27 17:38

bbsai hing,
actually,I really really told you that,you're the special one

bbsai

bbsai hing,
actually,I really really told you that,you're the special one
kfai 發表於 2009-8-28 01:52

kfai hing,
大家都鐘意玩影音...無乜 special 呀~~

bbsai

今日做過 test ~~ 個  table 都好真吓~~ 我個case 真係 ok ~

bbsai

bbsai hing,

小弟資質一般, 睇完只明部分. 不过有亇問題係依家set subwoofer phase多数同front speaker比較, 咁如果subwoofer同center phase 試左係180, subwoofer 同front 係0, 咁点簡呢? 重有subwoofer同 surroun ...
ryanenen 發表於 2009-8-29 10:59

ryanenen hing,
哈哈~~
所以昨日我做 test 去証實量最大 level 既 phase...
你有時間都可以玩玩...
我都有唸surround speaker compare with subwoofer...但海外無人講過...所以我無去理 lu ~