談錄音...

[Leo Yeh]

純粹吹吹水用..........:P

[Brachy]

純粹吹吹水用..........:P

難啊...............(sweat)(sweat)

[Leo Yeh]

最近在看一些文章

我邊看邊分享嘍

不過很多高手在旁邊潛水，要多多發言啦

[Leo Yeh]

首先要先研究的是立體聲雙麥克風的錄音方式

先借用DaYeh的這張圖開始

[Leo Yeh]

A/B Stereo Mic Technique



優點是靠近錄音源的話，錄音效果會非常好
缺點是立體定位不好，周圍的訊息也會損失

A/B is the most simple stereo technique to use. Quite simply, two microphones are pointed straight ahead at a source. This technique sounds surprisingly good on acoustic guitar and very close to the front while recording live; however, there's not much stereo image, if any, and a lot of ambient information is lost.

A/B is the preferred method of tapers who stack tape - taping close to the speakers to get a cleaner sound. However, A/B isn't as useful for taping further back, as a good stereo image is necessary for full reproduction of the event.

http://homerecording.about.com/od/mi...reo_mics_3.htm

[Leo Yeh]

A B Stereo 也稱為 Spaced Pair
(1)都常會使用兩隻電容式麥克風
(2) 若兩支麥克風的距離越遠，立體聲的寬度會越寬
(3) 在兩隻麥克風中間的樂器定位就會在中間，若樂器不在中間，雖然兩隻麥克風收到的聲音差不多，但靠近樂器的那隻會先收到音樂，會有相位差的問題，也就是重播時定位會跑掉
(4) 若兩隻麥克風距離太近，那立體聲的音場又會過小，也會太強調在中間樂器的聲音
(5) 可在中間加一隻麥克風再混音改善這問題 (Decca Tree?)

http://www.deltamedia.com/resource/s...echniques.html


Spaced Pair
With this method (also called AB), you place two identical mics a few feet apart and aim them straight ahead (Figure 4). The mics can have any polar pattern, but omni is most popular for this method. The greater the spacing between mics, the greater the stereo spread.

Figure 4. Spaced-pair technique.

[Leo Yeh]

來源：DPA

聲音大小與時間都會影響到立體聲音響重播的定位
(1) 左右聲音一樣，時間也一致，那聲音定位就會在中間0的地方開始
(2) 當一邊聲音大過另外一邊15dB或是時間差了1.12ms或是音量差了6dB及0.5ms的延遲組合，聲音定位就會在30度的地方開始

[Leo Yeh]

A是現場樂器的位置
B是正常音響重播的定位
C是太窄的錄音 (如兩隻麥克風擺得太近或是角度太靠近)
D是誇張分離了..(如兩隻麥克風擺得太遠或是角度太遠)

http://www.deltamedia.com/resource/s...echniques.html

Figure 1 shows three stereo localization effects. Figure 1A shows some instrument positions in an orchestra: left, left-center, center, right-center, right. In Figure 1B, the reproduced images of these instruments are accurately localized between the speakers. The stereo spread, or stage width, extends from speaker to speaker. (You might want to record a string quartet with a narrower spread).


Figure 1.
Stereo localization effects:
(A) Orchestra instrument locations (top view).
(B) Images localized accurately between speakers (the listener’s perception).
(C) Narrow-stage effect.
(D) Exaggerated separation effect.
A stereo pair of microphones can be angled apart, spaced apart, or both. Angling and spacing affect the stereo localization, as does the polar pattern of the microphones.
If you space or angle the mics too close together, you get a narrow stage width (Figure 1C).
If you space or angle the mics too far apart, you hear exaggerated separation (Figure 1D).
That is, instruments halfway to one side are heard near the left or right speaker.

要評論定位，一定要坐在喇叭中間，喇叭成60度的角度與在第10排聽交響樂的角度差不多

To judge stereo effects, you have to sit exactly between your monitor speakers (the same distance from each). Sit as far from the speakers as the spacing between them. Then the speakers appear to be 60 degrees apart. That is about the same angle an orchestra fills when viewed from a typical ideal seat in the audience (say, tenth row center). If you sit off-center, the images shift toward the side on which you're sitting and are less sharp.

[Leo Yeh]

來源DPA

(1) 電容式麥克風與AB Stereo錄音方式適合麥克風離演出聲音距離較遠時使用，因為其較指向性麥克風更能有完整的低頻。
(2) 錄音角度 (recording angle)與兩隻麥克風距離的決定，例如錄音角度140 => +-70 => 在+ - 30度再生 (1.1ms的時間差異) => 麥克風要距離40cm

[Leo Yeh]

來源：DPA

立體聲錄音的寬度跟頻率是有關的，因此想要更高品質的音調(tonal)，那麼麥克風之間的距離就要越寬，建議是最低音調波長的1/4左右，並且要考慮人耳對150Hz以下定位的能力，最佳距離在40~60cm左右。越近的麥克風距離用在接近發聲點以避免某個樂器太寬或不自然。若距離減少17~20cm，那是會被人耳所查覺的，這個距離約等於人兩耳間的距離。

要注意的是麥克風寬度越寬，那麼會影響系統再聲的定位能力，也會影響在Mono重播下的品質。

Since the stereo width of a recording is frequency-dependent, the deeper the tonal qualities you wish to reproduce in stereo, the wider your microphone spacing should be.Using a recommended microphone spacing of a quarter of the wavelength of the
deepest tone, and taking into account the human ear's reduced ability to localize frequencies below 150Hz, leads to an optimal microphone spacing of between 40 and 60 cm. Smaller microphone spacings are often used close to sound-sources to prevent the sound image of a particular musical instrument from becoming "too wide" and unnatural. Spacings down to 17 to 20 cm are detectable by the human ear, as this distance is equivalent to the distance between the two ears themselves.It should also be noted, that an increase in microphone spacing will decrease the system's ability to reproduce the signals from sound-sources positioned directly between the microphones.This will also lead to a reduction in the quality of the stereo recording when it is played in mono.