review33.com: 影音天地: 無低音的真正元凶-----駐波

分類搜尋 移民 | 借錢 | 投資 | 物流 | 搬運 | 按揭 | 樓盤 | 保險 | 機票 | 酒店 | 升學 | 補習 | 手錶 | 電腦 | 紅酒 | 網購 | 脫髮 | 健身 | 減肥 | 濕疹

影音天地主旨 ﹝請按主旨作出回應﹞ 上頁下頁首頁尾頁

寄件者

傳送日期

[#41] 無低音的真正元凶-----駐波 the correct page re JBL K2 should be issue no.168 pg.142-144 regarding the disappearance of 50hz.		xyz_ps 正式會員 203.xxx.xxx.173	2009-05-07 00:56

[#42] 無低音的真正元凶-----駐波
Interference and Stationary Wave are two different phenomenon in wave.

lts300

正式會員
210.xxx.xxx.123

2009-05-07 00:58

[#43] 無低音的真正元凶-----駐波
velocity = frequency * wave length
assume velocity of sound = 350 m/s
frquency = 60 hz
then, wave length = 5.83m

for the 60hz sound wave, Standing wave occures only if the distance between the speaker and wall is half of the wave length (ie 2.9m or his multiple). The node (no vibration point or smallest sound level) is in 2.9m and his multiple (2.9m*2, 2.9m*3, etc)
The anti-node (max vibration point) is 2.9m/2 = 1.45m or 1.45m+2.9m*n.
if the distance between the speaker and wall is not the mulitple of 2.9m, no stationary wave. The wave and his reflection wave will interfere each other only.

other conditions: one speaker only(no interference), the sound level should be very high(the amplitude of reflection wave is almost the same as the wave), the room is empty(no other interference).

lts300

正式會員
210.xxx.xxx.123

2009-05-07 01:35

[#44] 無低音的真正元凶-----駐波
I had already seen it school lab when I was a student.( about 20 years ago, hahaha)

lts300

正式會員
210.xxx.xxx.123

2009-05-07 01:45

[#45] 無低音的真正元凶-----駐波
I think we are talking about the effect of "first wall reflection" or "first reflection"

ackcheng

正式會員
210.xxx.xxx.250

2009-05-07 09:05

[#46] 無低音的真正元凶-----駐波
咁 wall reflection 係咪比較 standing wave 更重要, 更要考慮 ? Tks.

rickymartin

正式會員
116.xxx.xxx.2

2009-05-07 10:33

[#47] 無低音的真正元凶-----駐波
Thanks guys for your contributions. When more academic subjects are concerned, I must admit that I am totally a layman. Be it reflection or rebounce, stationary wave or standing wave, cancellation or interference, I hope those fever fans who used to deny the importance of room acoustic could also use their eyes to take a look of the experiment and eventually would understand where are the areas more worthwhile to deal with.

thomasc2

正式會員
202.xxx.xxx.165

2009-05-07 10:41

[#48] 無低音的真正元凶-----駐波
wave can not be "cancelled" by his reflection wave!
wave can be "cancelled" only by another identical wave with out of phase!
-------------------------------------------------

希望附圖有些解釋作用!

假若有左右平行的牆壁，某低音由15"單元發出，左行及右行波係唔會cancel的，如果cancel就唔會有駐波喇!
(駐波stationary Wave)＞＞＞簡單講，就係音波(或其他波)不能
散去他處，只能好係某地方彈來彈去)
低於70-80周的駐波，可以使人"誤解為"超低音"(如倒相管式超低音) 可是如果駐波是200周的話，booming/打心口就出現了!

這樣又會誤解為"低音好勁"!

navyseals

正式會員
218.xxx.xxx.88

2009-05-07 10:42

[#49] 無低音的真正元凶-----駐波
樓主可能講駐波cancel了其他音波(我想應該是mask了其他音波)

而人家誤解為駐波cancel自己＞＞所以不同意??

navyseals

正式會員
218.xxx.xxx.88

2009-05-07 10:47

[#50] 無低音的真正元凶-----駐波
咁 wall reflection 係咪比較 standing wave 更重要, 更要考慮 ? Tks.
-----------------------------------------------

駐波本來就係產生自"wall reflection" 他們是因果關係...

有人弄波浪牆，散射板，tube trap......都無非相"攪掂" 駐波....

navyseals

正式會員
218.xxx.xxx.88

2009-05-07 10:51

[#51] 無低音的真正元凶-----駐波
低音的長波是很難"對付"的，有時唯有自己改聽位，務求"減少"
駐波對你的影響......

試下走去喇叭後面或屋的他處，好采既，駐波就係果度"聽到"，你個位不一定聽到，咁就恭喜大吉!

navyseals

正式會員
218.xxx.xxx.88

2009-05-07 10:56

[#52] 無低音的真正元凶-----駐波
Someone pointed out : "in fact, stationary wave is not that easy to form"

If yes, "有人弄波浪牆，散射板，tube trap......都無非相"攪掂" interference, not stationary wave. Right? Thanks.

rickymartin

正式會員
116.xxx.xxx.2

2009-05-07 11:03

[#53] 無低音的真正元凶-----駐波
Stationary Wave就是一種interference,另一種係第一次反射對主聲波的影響.........

Stationary Wave是很難避免的，這是物理性所然......

唔好彩就"聽正" 我蝸居較"好彩" 小d!

navyseals

正式會員
218.xxx.xxx.88

2009-05-07 11:19

[#54] 無低音的真正元凶-----駐波
http://zh.wikipedia.org/w/index.php?title=%E9%A7%90%E6%B3%A2&variant=zh-tw

quote:-
駐波(standing wave)為兩個振幅、波長、週期皆相同的正弦波相向行進干涉而成的合成波。此種波的波形無法前進，因此無法傳播能量，故名之。

駐波通過時，每一個質點皆作簡諧運動。各質點振盪的幅度不相等，振幅為零的點稱為節點或波節(node)，振幅最大的點位於兩節點之間，稱為腹點或波腹(antinode)。

由於節點靜止不動，所以波形沒有傳播。能量以動能和位能的形式交換儲存，亦傳播不出去。
unquote.

navyseals

正式會員
218.xxx.xxx.88

2009-05-07 11:24

[#55] 無低音的真正元凶-----駐波
this is the best thread in 2009!

very useful.

last night I tried different spk/seat position, very interesting!

I looked into the stereosound, once more(I have read this book for many times in the past 4 months, still waiting for the new issue) and found:

1-they did emphasis on solving peak;
2-what they did in differnt settings also worked on the valley; though they also confirmed that elevate too much the valley will lead to distortion of the amp/spk.

lots to learn!

rover901

正式會員
202.xxx.xxx.140

2009-05-07 14:12

[#56] 無低音的真正元凶-----駐波
I use a "system test CD" to help me. The CD can tell me whether my system is OK in the existing position. The limitation is that the CD can't tell me where are the optimal positions of the speakers and the seat. It takes me more than a month by trial & error to set up my system properly. Very time consuming but it is worthy to do it.

rickymartin

正式會員
116.xxx.xxx.2

2009-05-07 14:26

[#57] 無低音的真正元凶-----駐波
一般業餘可以試下放pink noise然後用octave band or CPB analyzer等工具黎即時monitor頻響曲線黎改變喇叭擺位同埋搵聆聽位置會比較簡單快捷可靠, 更為low cost嘰應用可以放white noise然後用FFT analyzer..

有時間有資源嘰話當然係量埋ETF,RT,etc, 有足夠數據後仲可以對症下藥處理埋反射,殘響等問題..

當然居家嘰先天問題未必可以完全解決, 講到空間有完善規劃嘰標準聆聽室無可厚非點都一定有優勢..