1、 According to the construction requirements of the public address system, the construction should be carried out in accordance with the national standard of the People's Republic of China "Code for Construction and Acceptance of Electrical Equipment Installation Engineering" (CB50258-96), the safety industry standard of the People's Republic of China "Safety Prevention Work Procedures and Requirements" (GAT75-94), the "Code for Construction and Acceptance of Electrical Equipment Installation Engineering" (GBJ232-90, 92), and the design drawings of the public address system.
2、 Construction quality requirements: On site construction quality is a major issue directly related to whether the project can meet the design requirements and user requirements. Therefore, it is necessary to strictly follow the design plan, construct according to standards, without rework or idling, and keep a good construction log according to regulations. The following aspects should be mainly noted. 1. The selection and laying of cables in the construction process of public broadcasting systems often focus on the relevant equipment matching, while neglecting the selection of broadcasting transmission cables. In fact, for a public broadcasting system project, in order to achieve satisfactory sound effects, in addition to equipping high-quality broadcasting equipment (power amplifiers, speakers, etc.), the quality of broadcasting transmission cables also affects the sound quality to a certain extent. Due to the parasitic capacitance between parallel speaker lines, it is not suitable for long-distance transmission of broadcast signals, otherwise the high-frequency part of the sound will be attenuated, which can easily cause phenomena such as unclear high notes and muffled sound. Twisted pair cables can effectively overcome parasitic capacitance between wires, and twisted pair sheathed cables should be used for long-distance transmission of broadcast signals. Shielded twisted pair sheathed transmission cables, due to the shielding effect of the mesh, can effectively prevent the radiation impact of broadcast cables on other cables laid in the same pipe, and enhance the cable's tensile resistance, especially suitable for long-distance laying. In addition to using twisted pair cables, broadcast transmission cables also have certain requirements for wire diameter. In theory, the thicker the wire diameter, the smaller the transmission loss of the line, but the problem that comes with it is that the project cost increases and the construction difficulty increases. After weighing the pros and cons and considering the performance price ratio, broadcast transmission cables can be selected according to the following standards: cable name, cable length, broadcast transmission cable type, cable parameters, backbone cable 0-500m (vertical laying), shielded twisted pair sheathed cable cross-sectional area 2 × 1.5 mm2, backbone cable 0-500m (horizontal laying), twisted pair sheathed cable cross-sectional area 2 × 1.5 mm2, branch cable 0-300m (horizontal laying), twisted pair sheathed cable cross-sectional area 2 × 1.0 mm2, backbone cable 0-1000m (vertical laying), shielded twisted pair sheathed cable cross-sectional area 2 × 2.5 mm2, backbone cable 0-1000m (outdoor laying), shielded twisted pair sheathed cable cross-sectional area 2 × 2.0 mm2, backbone cable 0-2000m (outdoor laying), shielded twisted pair sheathed cable cross-sectional area 2 × 2.5 mm2. Cable 0-3000m (outdoor laying) The signal connections between all equipment in the public address system of shielded twisted pair sheathed cables with a cross-sectional area of 2 × 4.0 mm2 are balanced connections, and the endpoints are welded. If the system has a fire accident broadcasting function, flame-retardant copper core cables or fire-resistant copper core wires and cables should be used. The laying method of the line is through steel pipes or cable trays, and it is generally not allowed to be laid in the same cable tray as lighting and power lines. Fire protection measures should be taken for fire accident broadcasting lines. The bending radius of the cable should not be less than 15 times the diameter of the cable, and the power line should be laid separately from the signal line and control line. The length of the cable should be checked one by one, and the cable should be selected according to the length of each section on the design drawing, avoiding cable splicing as much as possible. When cables must be spliced, dedicated connectors should be used, and a moderate margin should be left at both ends of the laid cable, with clear permanent markings. 2. When connecting speakers and broadcasting lines to broadcasting equipment, special attention should be paid to the issue of phase consistency between each speaker and the broadcasting line. Otherwise, due to phase interference between speakers, there may be significant differences in sound pressure levels between points, resulting in serious consequences such as fluctuating sound levels throughout the entire hall. Therefore, during construction, it is necessary to strictly unify the line markings and regulations
Construction method of public broadcasting system
One connection method. Based on various audio construction requirements and practical effects in the project, there are three main methods for connecting speakers in public address systems:
Twisting method is to strip the outer skin of the broadcast cable and speaker lead end, divide each stripped head into two strands and twist them together, then wrap them with adhesive tape or clamp them with plastic sleeves. This method is simple and easy to construct, but it can easily cause problems over time.
The speaker inlet is connected to a socket. Simply peel off the broadcast cable end and insert it into the cable tray, then tighten the cable pressing screw. This method is currently widely used.
The welding method involves stripping the outer layer of the lead end, twisting it, soldering it with solder, and wrapping it with adhesive tape. This method is relatively cumbersome, but has good feasibility; Suitable for use in high demand or humid environments.
The above three connection methods depend on the specific situation and the requirements of Party A. But regardless of the method, tin plated wire should be used, which is convenient for welding and can also avoid rusting when exposed to moisture or for a long time. If it is required that the connecting wires cannot be exposed from the junction box to the speaker end, PVC threaded pipes or iron snake skin pipes should be used for protection.
3. The grounding broadcast control room of the system should be equipped with protective grounding and working grounding. To reduce the impact of the power supply system on the broadcasting audio system, protective grounding and working grounding should be set separately. The recommended practice is to lay a copper strip in each of the weak current shaft and the strong current shaft as the working grounding of the weak current system and the protective grounding of the strong current system, respectively. This can make the weak current system work better. Due to the fact that this method is a single point grounding when connecting to the ground, the total grounding resistance must not exceed 1 Ω.
3、 Construction inspection is necessary because the entire broadcasting system involves many connection points and connectors, and errors may occur during installation due to individual reasons. Therefore, a detailed inspection is necessary. General inspections include equipment installation safety checks, checks on whether the power supply lines are reasonable, and checks on whether the connections of various connectors are correct. Another important inspection item is to carefully check whether the status settings of each device meet the design requirements, especially for some speakers that have impedance matching switches
Please confirm if the switch is placed in the correct position. This must not be forgotten as it can easily cause equipment damage. These states also include whether the output selection switches of each signal source device are correct; Whether the function buttons of the signal processing equipment are appropriate; When the amplifier requires bridging, is the bridging switch set; Whether the power selection switch of each device is set to 220V, etc. After confirming the completion of the above construction steps, it is time to prepare for equipment debugging
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