Tips for designing public address system
(1) Transmission technology: the power feed method of the system software adopts the cable television broadcast transmission method.
(2) Provisions on line attenuation: In the public address system software, the line attenuation from the output of the amplifier machine equipment to the customer speakers far away from the line shall meet the following requirements:
·Business process broadcast shall not exceed 2 dB (at 1 kHz)
·Service broadcasting shall not exceed one decibel (at 1 kHz)
(3) The explosion-proof switch circuit with uniform output is adopted, and the output voltage is 70V or 100V.
(4) Capacity calculation method of power amplifier:
Calculation method of business public address system software and business public address system software: P=K1 × K2 ×Σ Po
Where: P - total rated output power of power amplifier (W);
Po--Ki × Pi, larger rated power (W) for each separate broadcast;
Pi -- rated capacity of customer's machinery and equipment in the ith division;
Ki -- additional demand coefficient of the ith separation;
For service broadcasting, the Ki of each variety show in the hotel room is 0.2-0.4;
Ki of music background variety show is 0.7-0.8
K1 -- line attenuation compensation index: 1.26 when the line attenuation is 1dB; 1.58 when the line attenuation is 2dB;
K2 - embrittlement index, generally 1.2-1.4;
·Calculation method of safety accident broadcasting system software: the system software has the following two methods:
A. The capacity of power amplifier shall be determined by 1.3 times of the number of software speakers of the system. B. The capacity of power amplifier shall be determined by 1.5 times of the number of larger three-layer speakers in the system software.
(5) Reservation of power amplifier
The power amplifier of public address system software shall be set with backup data power amplifier, and the power amplifier shall be delivered automatically or manually in case of common failure of power amplifier in operation. The reserved power amplifier of the power amplifier used for critical broadcasting (such as the power amplifier for safety accident broadcasting) should be able to be fully automatically delivered for use immediately in case of common failure of the amplifier in operation. The total number of reserved power amplifiers shall be determined according to the capacity of key broadcast loads.
(6) Speaker setting
·3W speaker boxes are set in offices, daily living rooms, changing rooms, etc· Ceiling mounted loudspeakers are generally used in building corridors, and the spacing of loudspeakers is considered as 2.5 times of the building height (ceiling height). Use 3-5W ceiling speaker.
·3-6W speaker box should be installed in the lobby, general meeting hall, hotel, shopping mall, leisure and entertainment club, etc.
·The control box of the bedroom bed in the hotel adopts 1W-2W speaker.
·Under the condition that the Japanese tatami floor in the architectural decoration design is high enough, the sound column or composition sound should be used for large capacity sites.
·The horn speaker shall be used when setting speakers in noisy, wet and cold places. The noise coefficient of the horn speaker used in the noisy site should be 10-15dB higher than the noise.
(7) Regulations for power supply system of broadcasting system software
·The broadcasting station with small capacity can be powered by the power socket immediately; When the capacity is above 500W, the broadcast main control room is set, and its power supply system can be transported by the current controller dedicated line in the principle of proximity· The AC current deviation value is generally not suitable for more than 10%. When the working voltage deviation cannot take into account the limited provisions of the machine equipment, the full automatic voltage regulator equipment shall be installed around the machine equipment.
·The AC capacity for broadcasting is generally 1.5-2 times of the AC current consumption capacity of the final broadcasting machinery and equipment.
·Fire power is used for safety accident broadcasting equipment.
(8) Selection of transmission cable
·Copper-core multi-core cable or copper-core plastic stranded wire should be used for the hotel room service broadcast line.
·Other broadcast lines should use copper core plastic stranded wire.
·Shielded cables shall be used for power lines of various variety shows.
·Fire retardant copper core cable or fire retardant copper core cable wire shall be used for safety accident broadcast line.
(9) Line laying mode
·The line is paved through seamless steel pipe or wire slot, and cannot be laid with lighting fixtures and cable in the same wire slot.
·Fire safety assurance measures shall be taken for safety accident broadcast lines.
