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1、RBA - 1,线阵列扬声器原理 Principles of Line Arrays,R Bob Adams International Director rbobSLS ,SLS AUDIO Ozark, Missouri www.SLS,线阵列是一种扬声器单元的阵列方式，它可以对声音进行良好的控制，并在产生反馈之前提供适当的增益。 Line Arrays have been recognized as a loudspeaker design that can provide excellent control and gain before feedback.,为了合理得当地使用线阵列扬
2、声器，设计者必须明确扬声器设计和操作的一些基本原理。 To properly use Line Arrays, the designer must understand some basic principals of loudspeaker design and operation.,为了合理得当地使用线阵列扬声器，设计者必须明确扬声器设计和操作的一些基本原理。 To properly use Line Arrays, the designer must understand some basic principals of loudspeaker design and operation.
3、,线阵列扬声器 Line Arrays,早期的线阵列扬声器 Early Line Array,标准的扬声器结构 Standard Loudspeaker Construction,标准的扬声器是点声源 Standard Loudspeakers are POINT SOURCE devices,标准的扬声器结构 Standard Loudspeaker Construction,点声源的声学特性 POINT SOURCE characteristics,球面波辐射 Spherical wave propagation,Spherical = 球状,声波传播以三维的方式进行 Waves spre
4、ad in 3 dimensions,标准的扬声器结构 Standard Loudspeaker Construction,球面波的辐射特性 Spherical Wave Propagation,点声源的声学特性 POINT SOURCE characteristics,声波以三维的方传播 Waves spread in 3 dimensions,当距离增加一倍时，因为距离产生的损耗 = -6 dB Loss over Distance = -6 dB per doubling of distance,这就是所谓的平方反比定律 Know as the Inverse Square Law,损耗
5、dB = 20*LOG Dft/3.28 LossdB = 20*LOG Dft/3.28,标准的扬声器结构 Standard Loudspeaker Construction,数学的基本原理 The Mathematic Fundamentals,理论上的点声源： A theoretical point source: 2 X 半径 R = 4 X 面积 2 X the radius R = 4 X the area4 X 面积 = 能量, 或 6 dB 声压级损失 4 X the area = power, or a 6 dB loss of level因此，平方反比定律为：距离每增加一倍
6、损失6dB Thus the inverse-square law: 6dB per doubling of distance,Courtesy of Ulysses Line Array Research,标准的扬声器结构 Standard Loudspeaker Construction,线阵列的特性 Line Array Characteristics,柱面波辐射 Cylindrical wave propagation,柱体 Cylinder = 纵向的 Strait forward projection,声波以二维的方式传播 Waves spread in only 2 dimens
7、ions,线阵列利用声波干涉原理（增强或减弱）来限制声波的辐射角度Line Arrays use the physics of interference effects (summation and cancellation) to restrict wave spreading,线阵列 Line Array,柱面波 cylindrical wave,线阵列的特性 Line Array Characteristics,柱面波辐射 Cylindrical wave propagation,当距离每增加一倍时，距离所造成的损耗=-3dBLess Loss over Distance =-3 dB
8、per doubling of distance,只适用于近场 Near Field only,数学的基本原理 The Mathematic Fundamentals,理论上的无限线声源 A theoretical infinite line-source: 2 X 半径 R = 2 X 面积 2 X the radius R = 2 X the area2 X 面积 = 能量, 或 3dB 的声压级损失 2 X the area = power, or a 3dB loss of level因此，无限点声源在距离增加一倍时，只损耗3dB Thus infinite line sources
9、loose only 3dB per doubling of distance,Courtesy of Ulysses Line Array Research,平方反比定律 Inverse Square Law,线阵列系统 Line Array Systems,普通系统 声级以dB计 Conventional System SPL in dB,平方反比定律 Inverse Square Law,比较 Comparison,线阵列的特征 Line Array Characteristics,距离每增加一倍，距离引起的损耗=-3dB Less Loss over Distance =-3 dB p
10、er doubling of distance,只适用于近场 Near Field only,一个设计者如何决定线阵列的近场或远端场呢？ How does a designer determine the Near Field or Far Field of a Line Array?,例：Example 线阵列 Line array = 4m高 4m tall 近场（D）Near Field (D) = 25米 25 meters,近场/远场的概念 Near Field / Far Field Concept,所有有限线声源在一定距离后会转变为点声源 All finite line-sour
11、ces transition into point-sources at some distance,我们把这个转变距离称作该线声源的临界距离 We will call the center of this transition area a line sources Critical Distance,这是因为在远距离的听众看来，声源更像是一个点而不是线 This is because the size of the source, from the perspective of the distant listener, is more similar to a point than a
12、line,数学的基本原理 The Mathematic Fundamentals,Fresnel vs. Fraunhofer 近场和远场的比较 near-field vs. far-field,数学的基本原理 The Mathematic Fundamentals,基本线阵列扬声器频率耦合的几何学Basic Line Array Geometry for Frequency Coupling,基本线阵列扬声器频率耦合的几何学 Basic Line Array Geometry for Frequency Coupling,最大耦合波长 H Highest coupling H,最大耦合波长
13、H Highest coupling H,为了合理地耦合所有超过5kHz的频率， 换能器件必须小于2.67”（6.8cm）To properly couple any frequency above 5 kHz, the transducers must be spaced less than 2.67” (6.8 cm),这对实际设计来说是完全不现实的Completely unrealistic for a practical design,线阵列如果建立在一堆简易扬声驱动单元的堆砌上，是不可能在高频下作为线声源使用的 NO line array, based on a simple sta
14、ck of cone drivers, can perform as a line source at high frequencies,垂直1米长的带有一组4” 间隔驱动单元的线阵列Vertical polars of a 1-meter line array with a 4” driver spacing,4” 间隔 = 3384Hz，所以大致看来，1600Hz 的驱动间隔大概为 ， 3150Hz 大概为 1 ，6300Hz 大概为 2 .4” spacing = of 3384 Hz, so at roughly 1600 Hz the drivers are apart, at 31
15、50 Hz they are 1 apart, and at 6300 Hz they are 2 apart,在1 的图里，在第一对突起处，高阶的倾斜分支出现在轴向的上方和下方At 1, the first pair of prominent, high-level gradient lobes appear above and below the main lobe,线阵列未被适当耦合的情况Line Array - not properly coupled,辐射不连续 Dispersion inconsistent,声压级分布不规律 SPL irregularity,线阵列 Line Array,近场计算的数学原理 Heavy Math for Near Field calculation,Where: F 代表频率 F is frequency C 代表声音的传播速度 C is speed of sound H 代表阵列的高度（英尺） H is array height in feet R 代表距离 R is distance,
