Diffraction Grating,Diffraction Gratings,Grating Optics,Holographic diffraction grating, Holographic Grating Changchun Realpoo Photoelectric Co., Ltd. , https://www.optics-realpoo.com Before discussing the linear array of cylinders, let's take a look at the two main types of linear arrays. Linear arrays are mainly divided into modular linear arrays (Modular Line Array) and cylindrical linear arrays (Column Line Array). First, let's talk about what is a modular linear array.
The modular linear array is also known as the "Concert Line Array". Initially, when modular linear arrays appeared in the audio market, they were mainly used for sound reinforcement in concerts. Thus, the name "concert" linear array was used. Modular linear arrays refer to the vertical arrangement of individual speaker units (or module modules) combined with the sound propagation characteristics of all independent speakers, resulting in a linear array-specific, wide lateral, and narrow longitudinal sound coverage. (Note: Linear arrays are not strictly vertical alignment systems, and they sometimes appear in a horizontal arrangement, such as a heart-shaped subwoofer linear array). We often see modular linear arrays (JArray) shaped like the letter J. Obviously, that is to increase the vertical coverage of the bottom of the linear array, so that the front listening area gets a better sound coverage. Depending on the application and the original design of the different manufacturers, the angle between each individual speaker unit can be extended from 1 to 12 degrees. But the larger the angle, the more the linear array characteristics will be lost in some bands. At the same time, in order to meet different application requirements, modular linear arrays are also divided into different types and models such as large modular and small modular. The more representative large modular linear arrays are JBL's Vertec, and the small QSC's WideLine8. Picture 1 is a 10-degree slanted letter J modular linear array.
Let's talk about what is a Column Line Array.
We might think of a cylindrical linear array as a cylindrical speaker, which also has a linear array of sound propagation characteristics. Unlike a modular linear array that vertically aligns individual speaker units (or module modules), the cylinder speakers arrange the same drive units in a separate cylindrical box to achieve the physical environment required for a linear array. . At present, the cylindrical speakers on the market are divided into active active and passive passive. More representative active cylinder speakers are Duran Audio's Intellivox and Renkus-Heinz's Iconyx, and passive cylindrical speakers are Bose's MA12. Picture 2 is a side perspective view of a cylindrical speaker.
After understanding the basic characteristics and construction of linear arrays and cylindrical speakers, I would like to focus on the application of cylindrical speakers in sound engineering. In the process, I want to discuss some technical application problems in a simple language. This discussion does not include the coverage formula, or the calculation of speech intelligibility. If you want to learn and understand the formula calculation principle of linear arrays, I recommend that you read MarkS.Ureda published in May 2001 at the ASE Annual Conference Paper Arrays: Theory and Applications. (Linear Array: Theory and application)
The application place and environment of the column speaker:
The cylindrical speaker has excellent vertical sound coverage control. In an acoustic environment with long reverberation time, it can accurately deliver direct sound to the listening area instead of to the ceiling, side walls, or the ground. Thereby the influence of strong reflected sound on sound quality and speech intelligibility is avoided. For example, airport halls, train station waiting rooms, and any large public spaces with long reverberation time and highly reflective acoustic environment are suitable for building a main sound reinforcement system using cylindrical speakers.
Cylindrical speakers can be used in lower ceiling rooms to take advantage of the linear array's sound characteristics. For example: conference rooms, audio-visual rooms, etc. Due to height and space restrictions, it is not allowed to hoist in front of the room, or install a common point source speaker on the side wall. Even if it is possible, the middle and rear listening areas cannot get enough direct sound coverage from the front speakers because of the height limitations of the speakers. If you want to solve this problem, you must install a delay speaker to cover the middle and rear listening areas. Although this method can solve the coverage problem of the direct sound in the middle and rear listening areas, it destroys the real sound image positioning and increases the difficulty of system debugging in the later stage, and also increases the construction cost and construction time. In this case, if you use a cylindrical speaker to build the main sound reinforcement system, just a series of problems can be solved. Install the column speakers on the front or sides of the wall to cover the entire listening area. Because the linear array characteristics of the cylindrical speaker make it reduce the direct sound pressure by only 3dB at the near-field multiple distance, the cylindrical speaker can transmit the sound farther, without the need to install a delay speaker, the cylinder The speakers cover the entire listening area on average. At the same time, because it has a low-profile slim box, the installation is simpler and the appearance is much more beautiful than the point source speaker.
Taking this application as an example, another important advantage of the cylinder speaker is the anti-feedback. Typically, in a conference room using a point source speaker system, or other similar application environment, the sound system is susceptible to feedback. Because the point source speaker has diffused sound propagation characteristics, or it does not have good coverage control, it is easy to transfer too much direct speaker sound to the area where the microphone is located, so that the sound system produces a transient infinity. The signal loop, that is, the feedback. The cylindrical speaker is just the opposite. It has superior sound vertical coverage control, and the direct sound transmission track is easy to control, and the microphone area is not subject to too much interference, thus avoiding feedback. Even if the microphone is placed very close to the column speaker, the sound received by the microphone is only the direct sound of one or two of the many drive units of the column speaker. Although the microphone receives a high sound pressure level at this time, it is not the total output energy of the entire column speaker, so it is not easy to generate feedback. Picture 3 is a three-dimensional spherical sound contrast image of a point source speaker and a cylinder speaker at 2000 Hz.
Cylindrical speakers perform well in a variety of applications due to their linear array of acoustic characteristics and a low profile slim case. But the column speaker also has its application limitations. First of all, the maximum sound pressure level output of the column speaker is much smaller than that of the point source speaker, which is not suitable for applications requiring high sound pressure level. Secondly, the sound transmission surface of the passive column speaker is fixed at 90 degrees to the cabinet. Because it has a narrow longitudinal coverage angle, the speaker cannot be installed too high, or the cabinet is oriented when the speaker is installed at a high position. The lower tilt angle is also not recommended to be greater than 5 degrees. At the same time, passive column speakers can only provide a sound coverage and cannot form a group of speakers like a point source to create a composite sound coverage. For example, a six-point sound source speaker is used to form a speaker group. The top three cover the listening area of ​​the theater hall, and the lower three cover the first layer listening area. However, the active column speaker can set the delay amount of each drive unit to achieve a downward tilt of -35 degrees or even lower in the case of vertical installation of the cabinet. This solves the problem that the column speaker cannot be installed too high. With the delay adjustment function, the cylinder speaker can also be divided into two different sound coverage areas. That is to say, the drive unit on the upper part of the speaker forms an upward coverage surface for covering the listening area of ​​the hall. The lower drive unit forms a straight or downward coverage for covering the first layer of listening area. However, the price of active column speakers is so high that many customers who want to use it are discouraged. On the other hand, the cylindrical speakers currently on the market are basically all-frequency, or two-way drive unit design. The disadvantage of this design is that the distance between the driving units cannot be optimized according to the wavelengths of different frequency bands, so that a stable wide-band linear array response characteristic cannot be obtained, resulting in loss of coverage control of certain frequency bands. This problem has plagued many column speaker designers. Finally, cylindrical speakers are not suitable for outdoor applications because they are not waterproof.
Fortunately, after years of market research and product development, the US Community Audio Company launched the world's first three-way all-weather column speaker Entasys at the InfoComm 2008 conference in the United States. It not only integrates the existing characteristics of the column speaker, but also solves the design flaws of the existing column speaker. Thereby greatly improving the usability of the column speaker. Whether it is indoors or outdoors, it has excellent performance. Since Entasys was released in the European and American audio market, it has been sought after by many famous system designers and end users. Picture 4 is the CommunityEntasys full-range and low-frequency cylindrical speaker.
Entasys is divided into full-range speakers and low-frequency speakers. They have the same size and appearance, but different internal structures. By combining the full-range speakers with the low-frequency speakers through different superposition methods, different coverage effects are obtained to meet various application requirements. The full-range speaker consists of six 3.5-inch low-frequency units, 18 2.5-inch IF units, and 42 CommunityCRE high-frequency units (compactRibbonEmulators). The low frequency speaker contains six 3.5-inch low frequency units. The powerful combination of drive units enables an Entasys full-range speaker to be at 100 feet and a direct sound pressure level of 96dBSPL, which solves the problem of insufficient sound pressure level of ordinary cylindrical speakers. At the same time, because of the three-way design, the distance of each drive unit is fully optimized, resulting in a stable wide-band linear array response. For outdoor waterproofing, Entasys uses Community's world-leading speaker waterproofing technology. It uses an aluminum water-like casing and all drive units are made of waterproof material. This waterproof design fully realizes the sound reinforcement application of the column speaker outdoor. In order to get the composite coverage function of the active column speaker, Community engineers created a composite coverage effect similar to the active column speaker in the system design by superimposing the low frequency speaker and the full frequency speaker. Users get the unique features of an active column speaker when using a relatively inexpensive passive column speaker. Entasys recommends up to five stacks. We can stack five Entasys to form an array of cylinders (two full frequencies above and below, one low frequency in the middle), and cover the listening area of ​​the hall with two full-range speakers. The two full-range speakers below cover the first floor. In the listening area, a low frequency in the middle connects the upper and lower full frequencies to maintain the physical characteristics of the linear array and create two different coverages, while achieving lower low frequency control. The drive unit of the Entasys full-range speaker uses a modular design. The user can adjust the drive unit module to a vertical structure as needed, bend the structure up and down separately, or bend the structure up and down simultaneously (Entasys factory settings). Using these adjustments, you can extend its vertical coverage angle from 6 to 12 degrees. Depending on the application, give it a wider vertical coverage up, down or overall. Entasys woofers are essential when creating a cylindrical array of composite coverage. At the same time, superimposing the low-frequency speakers above or below the Entasys full-range speakers also gives the cylinder array a lower, controllable low frequency. Here, I would like to introduce another major function of the Entasys low frequency speaker: low frequency coverage control.
Entasys' low frequency speakers are not used to boost the system's low frequency response because it is not a subwoofer. Its main role is to get a lower frequency control range. We know that the linear array has a wide lateral coverage angle and a very narrow vertical coverage angle. However, in practical applications, the low frequency band of a linear array often does not have this characteristic. The lowest frequency controllable by the linear array is proportional to the length of the entire array, and the longer the array, the lower the controllable low frequency. Based on this principle, if it is necessary to strengthen the control of the low frequency coverage of the cylinder array, Entasys low frequency speakers can be superimposed on the cylinder array to increase the overall length of the array and obtain lower frequency control to avoid excessive low frequency leakage. The low frequency is strongly reflected, which triggers the room's low frequency resonance (roommode) and system low frequency feedback. When designing a sound system for a room with long reverberation time, it is especially important to enhance the coverage control of the low frequency. There is a question here, why not use Entasys full-range speakers to increase the overall length of the cylinder array? As I mentioned earlier, the Entasys full range speaker provides an excellent long range depth coverage and high SPL output. Many times, using one or two Entasys full-range speakers, you can fully meet the design requirements for depth coverage and direct sound pressure levels. Superimposing one or two Entasys full-range speakers on the original cylinder array can of course increase the overall length of the array to enhance the control of low frequencies. At the same time, however, the superimposed full-range speakers produced excessive depth coverage and direct sound pressure (unlike point source speakers, the linear array source doubled and the direct sound increased by 6 dB). As a result, more acoustic reflections are triggered, increasing the complexity of the acoustic environment and ultimately destroying the sound quality of the project. Therefore, the depth coverage distance and the direct sound pressure level of the cylinder array have met the design requirements, but when it is necessary to strengthen the control of the low frequency, the use of low frequency speaker superposition is the correct choice. In addition, the engineering budget is saved because the price of full-range speakers is more expensive than low-frequency speakers. Picture 5.1 is an array of Entasys full-range speakers at 50 meters. In the picture we can see that the low frequency below 250Hz is basically uncontrolled. Figure 5.2 shows an array of Entasys full-range speakers and two low-frequency speakers superimposed at 50 meters. We can see that the lowest control frequency of the low frequency has reached 125Hz. From the design of the Entasys cylinder speaker, we can feel the deep design skills of Community Chief Design Engineer Bruce Howze, and the entire Community design team.
The design concept of “serving customers with technologyâ€. 
