Audio Power Distribution is Crucial, Otherwise Main PA, Monitors, and Stage Mix Might 'Conflict'!
In large halls, for better localization of the speaker system, it's ideal for the audience to 'see' the speakers, aligning visual and auditory directions. This is because horizontal localization is more acute for hearing, while vertical localization is relatively dull.
If appropriate delay is inserted into the main speaker system, utilizing the Haas effect to shift the sound image downwards, bringing the speaker system's sound source direction closer to the actual source, the listening experience will be further improved.
Auxiliary speaker systems beyond the main PA generally vary. For example, ceiling speakers are used in corridors and lounges for background music, while compact speaker systems or small columns might be used in small VIP meeting rooms.
In such cases, group the speakers appropriately based on their power, impedance (or voltage), and quantity, performing necessary parallel or series connections before linking to the power distribution panel. Based on the overall power distribution, design a switchable connection circuit to the power amplifiers, selecting a backup amplifier system for convenient control and operation from the control room. Additionally, the power requirements for the monitor and foldback systems must be determined.
2. Foldback System & Required Power
The foldback system (stage monitors) is specifically built to address the listening needs of performers and musicians on stage. During a performance, artists are behind the main PA speakers. If they cannot hear themselves clearly, they lose their performance feel. Therefore, for theaters and entertainment venues, a foldback system is essential alongside the main PA system.
Furthermore, if the main PA fails, the foldback system can serve as an emergency sound system to prevent a complete blackout situation. Generally, foldback system power is set at 20% of the main PA power. For example, a 2000W main PA would require a 400W foldback system.
In the foldback system, for appropriate volume and clarity, the monitor amplifier power should be about 1.3 times the monitor speaker power. In practice, the foldback amplifier output power needs on-site adjustment. Insufficient foldback power renders the system useless; excessive power overshadows the main PA and easily causes feedback. Hence, careful attention must be paid to foldback system volume and effect adjustment.
3. Control Room Monitoring System & Required Power
The control room monitoring system is specifically built for the sound operator's listening needs. During a show, the main speakers are in the isolated main hall/venue. The operator cannot directly hear the main speaker output or their own mixing clearly, making work impossible.
Therefore, a monitoring system synchronized with the main PA must be installed in the control room. This helps the operator understand the main hall's sound and make real-time adjustments. Hence, a monitoring system is essential for all types of venues.
Generally, monitoring system power is set at 10% of the main PA power. For example, a 2000W main PA would require a 200W monitoring system. In this system, to monitor undistorted sound, the monitor amplifier power can equal the monitor speaker power.
In practice, the monitor amplifier output power needs on-site adjustment. Insufficient monitoring power is pointless; excessive power makes the control room too noisy, hindering work. Therefore, adjust the monitoring system to a suitable volume before the program starts.
Total subwoofer power can be 0.5 to 1.5 times the total main speaker power. Take the upper limit for discos, the lower limit for multi-function halls. For speech-only reinforcement, subwoofers may be omitted.
Other surround speakers, rear fill speakers, foldback speakers, etc., can have power ranging from 1/10 to 1/2 of the main speakers (AC-3 systems require surround speakers equal to the mains).
4. System Type Selection
In a sound reinforcement system, sound quality entirely depends on every component functioning well. Equipment performance is a key indicator of the system's ability to work optimally and stably. Therefore, system component selection is as critical as acoustic design and system engineering.
Professional sound systems have amplification formats like mono, stereo, and surround sound. Only after selecting the amplification format can equipment selection proceed.
Mono Reinforcement
Mono reinforcement is currently the primary format in domestic halls. Its advantages are simple system structure, low investment, and ease of control.
Depending on the system's specific use, stereo capability might be unnecessary. This allows halving the peripheral equipment (e.g., room EQ, compressor/limiter, delay) by using single-channel (mono) units, significantly reducing cost. This is an economical and practical design for venues primarily used for speech, like conference halls.
Stereo Reinforcement Format
Stereo offers superior image localization, clarity, and layering compared to mono. In practical electroacoustic systems, 70mm cinemas often use stereo playback for high alignment of sound image with visual image, creating a realistic sense of space and depth.
However, among domestic theaters and halls, few currently adopt stereo. In stereo-equipped venues, perfect stereo isn't achievable in all seats. Often, sound quality in some seats is worse than with mono.
The reason is the limited effective listening area of the two-channel stereo format. To ensure all listeners experience stereo in a hall designed for it, seat numbers might need reduction. Hall design, speaker placement, and control become more complex.
Implementing stereo in a hall not originally designed for it often backfires. The result: a small minority experiences perfect stereo; the majority perceives no advantage.
From an equipment perspective, modern gear generally has basic stereo capabilities. The core mixer usually has basic stereo functions: a 'Panorama' (Pan) pot, Left/Right outputs. Therefore, other equipment, amps, and speakers are configured in Left/Right pairs, enabling stereo amplification.
Older hall designs often can't meet stereo requirements. The common practice is to set the mixer's 'Pan' to center, effectively downgrading the stereo equipment to mono.
In essence, current electroacoustic system designs often adopt this approach: Ensure basic stereo functionality in the equipment; but considering the hall's structure and seating, use mono reinforcement for broad coverage. Most entertainment venues follow this pattern.
Many entertainment venues and multi-function halls use the above strategy: Retain stereo capability in the equipment configuration but use it in mono during operation. Since design requirements for these venues aren't uniform, the amplification format should be flexible.
For example, use a combination of stereo and mono: Apply stereo reinforcement in prime seating/dance floor areas, and mono elsewhere. The core principle: Ensure all listening areas receive the complete program. Avoid excessive speakers or irregular placement causing destructive wave interference.
Surround Sound
Builds upon standard stereo, enhancing spatial sense and image solidity. It's an advanced format installed in some new cinemas and theaters domestically.
5. Equipment Selection
Speakers
Speakers are the voice of the entire system, hence the primary consideration. Speaker selection starts with sensitivity and rated power to determine power per source. Use speaker directivity to analyze and control the hall's sound field, determine each speaker's position, input impedance, and input power. Calculate matching power between speakers and amplifiers.
Power Amplifiers
To ensure overall sound quality, amplifiers need sufficient power headroom and long-term stability. Selected amplifiers should have robust technical measures for efficiency, low distortion, short-circuit/no-load protection, and thermal management.
Mixers & Other Equipment
The mixer is the heart of the sound system. It must have good electrical performance, stable operation, flat frequency response, minimal harmonic distortion. Mixers vary greatly in functionality; choose based on the system's requirements for input channels and output groups.
Furthermore, based on the hall's acoustics, select appropriate EQs, delays, reverbs, compressors/limiters, frequency shifters, etc., to form a normal, stable, and reliable sound reinforcement system.
Source Equipment
Source components include FM/AM broadcast reception/relay, record (including CD) and tape playback equipment. Since source levels are low, all components/devices must ensure high sensitivity, high S/N ratio, low distortion, and high reliability.
Microphone Selection
Microphones are the first 'entry point' of the system. Natural sound converted to voltage by the mic is amplified thousands of times by the mixer and power amp before reaching the speakers.
Microphone quality directly impacts system quality; its characteristics directly affect pickup and reproduction; placement directly affects system gain before feedback; signal connection directly affects S/N ratio. Correct microphone use is key to the entire audio system performing well.
Microphone selection must match the acoustic environment and sound source. Base choices on the overall system requirements, application scenario, sound source characteristics, mic specifications, and hall features.
6. Conduit Design
Fixed-installation systems typically run mic and instrument cables from the stage to the control room, and amplifier outputs to speakers. These cables should be run in conduit.
Metal Conduit Installation
This refers to running mic input lines and speaker output lines outside the control room. Although shielded cable is used, for permanent installation, whether concealed or surface-mounted, metal conduit is preferred.
Benefits of metal conduit:
① Protects cables from damage;
② Provides excellent shielding against electromagnetic interference;
③ Allows conduit installation first, cable pulling later—very convenient—and easier cable replacement. In new/renovated halls, conduit design is crucial for undistorted signal transmission.
Conduit Design Key Points
To reduce induced noise, mic input lines often use twin-core shielded cable and MUST be run in metal conduit. For exceptionally long runs, avoid proximity and parallel routing with power cables.
Since mic positions may change, pre-install multiple junction boxes during design. Equip each with XLR sockets. Position them appropriately (e.g., inside stage side walls, under stage front/band floor, under VIP/referee stands). Pre-wire all junction boxes for easy access.
For speaker cables, to ensure power delivery and damping match between amp and speaker, simply choose sufficiently thick wire run in conduit. For the main PA, use a ring ('daisy-chain') wiring method per group for reliability. This ensures the entire main PA keeps working even if any point in a group breaks. Once control room location, mic socket boxes, and speaker positions are fixed, design an economical and rational conduit layout avoiding strong interference, based on the building structure. Produce a construction plan drawing.
7. Conduit Installation Process
Note these points during conduit installation:
(1) Run lighting and audio cables in separate conduits, maintaining at least 1m spacing when parallel. Maintain at least 0.5m spacing when crossing perpendicularly. Avoid parallel runs if possible.
(2) When pulling 3+ cables through one conduit, total conductor cross-section shouldn't exceed 40% of the conduit's internal area. For two cables, conduit area should be >1.2 times cable cross-section.
(3) For ease of pulling: Max length 50m for straight runs; 30m for 1-2 bends; 15m for 3-4 bends. Exceeding these requires junction boxes for segmented pulling.
(4) Conduit MUST be grounded to prevent interference. All conduit and junction boxes must form a continuous, grounded system—this is vital.
If appropriate delay is inserted into the main speaker system, utilizing the Haas effect to shift the sound image downwards, bringing the speaker system's sound source direction closer to the actual source, the listening experience will be further improved.
Auxiliary speaker systems beyond the main PA generally vary. For example, ceiling speakers are used in corridors and lounges for background music, while compact speaker systems or small columns might be used in small VIP meeting rooms.
In such cases, group the speakers appropriately based on their power, impedance (or voltage), and quantity, performing necessary parallel or series connections before linking to the power distribution panel. Based on the overall power distribution, design a switchable connection circuit to the power amplifiers, selecting a backup amplifier system for convenient control and operation from the control room. Additionally, the power requirements for the monitor and foldback systems must be determined.
2. Foldback System & Required Power
The foldback system (stage monitors) is specifically built to address the listening needs of performers and musicians on stage. During a performance, artists are behind the main PA speakers. If they cannot hear themselves clearly, they lose their performance feel. Therefore, for theaters and entertainment venues, a foldback system is essential alongside the main PA system.
Furthermore, if the main PA fails, the foldback system can serve as an emergency sound system to prevent a complete blackout situation. Generally, foldback system power is set at 20% of the main PA power. For example, a 2000W main PA would require a 400W foldback system.
In the foldback system, for appropriate volume and clarity, the monitor amplifier power should be about 1.3 times the monitor speaker power. In practice, the foldback amplifier output power needs on-site adjustment. Insufficient foldback power renders the system useless; excessive power overshadows the main PA and easily causes feedback. Hence, careful attention must be paid to foldback system volume and effect adjustment.
3. Control Room Monitoring System & Required Power
The control room monitoring system is specifically built for the sound operator's listening needs. During a show, the main speakers are in the isolated main hall/venue. The operator cannot directly hear the main speaker output or their own mixing clearly, making work impossible.
Therefore, a monitoring system synchronized with the main PA must be installed in the control room. This helps the operator understand the main hall's sound and make real-time adjustments. Hence, a monitoring system is essential for all types of venues.
Generally, monitoring system power is set at 10% of the main PA power. For example, a 2000W main PA would require a 200W monitoring system. In this system, to monitor undistorted sound, the monitor amplifier power can equal the monitor speaker power.
In practice, the monitor amplifier output power needs on-site adjustment. Insufficient monitoring power is pointless; excessive power makes the control room too noisy, hindering work. Therefore, adjust the monitoring system to a suitable volume before the program starts.
Total subwoofer power can be 0.5 to 1.5 times the total main speaker power. Take the upper limit for discos, the lower limit for multi-function halls. For speech-only reinforcement, subwoofers may be omitted.
Other surround speakers, rear fill speakers, foldback speakers, etc., can have power ranging from 1/10 to 1/2 of the main speakers (AC-3 systems require surround speakers equal to the mains).
4. System Type Selection
In a sound reinforcement system, sound quality entirely depends on every component functioning well. Equipment performance is a key indicator of the system's ability to work optimally and stably. Therefore, system component selection is as critical as acoustic design and system engineering.
Professional sound systems have amplification formats like mono, stereo, and surround sound. Only after selecting the amplification format can equipment selection proceed.
Mono Reinforcement
Mono reinforcement is currently the primary format in domestic halls. Its advantages are simple system structure, low investment, and ease of control.
Depending on the system's specific use, stereo capability might be unnecessary. This allows halving the peripheral equipment (e.g., room EQ, compressor/limiter, delay) by using single-channel (mono) units, significantly reducing cost. This is an economical and practical design for venues primarily used for speech, like conference halls.
Stereo Reinforcement Format
Stereo offers superior image localization, clarity, and layering compared to mono. In practical electroacoustic systems, 70mm cinemas often use stereo playback for high alignment of sound image with visual image, creating a realistic sense of space and depth.
However, among domestic theaters and halls, few currently adopt stereo. In stereo-equipped venues, perfect stereo isn't achievable in all seats. Often, sound quality in some seats is worse than with mono.
The reason is the limited effective listening area of the two-channel stereo format. To ensure all listeners experience stereo in a hall designed for it, seat numbers might need reduction. Hall design, speaker placement, and control become more complex.
Implementing stereo in a hall not originally designed for it often backfires. The result: a small minority experiences perfect stereo; the majority perceives no advantage.
From an equipment perspective, modern gear generally has basic stereo capabilities. The core mixer usually has basic stereo functions: a 'Panorama' (Pan) pot, Left/Right outputs. Therefore, other equipment, amps, and speakers are configured in Left/Right pairs, enabling stereo amplification.
Older hall designs often can't meet stereo requirements. The common practice is to set the mixer's 'Pan' to center, effectively downgrading the stereo equipment to mono.
In essence, current electroacoustic system designs often adopt this approach: Ensure basic stereo functionality in the equipment; but considering the hall's structure and seating, use mono reinforcement for broad coverage. Most entertainment venues follow this pattern.
Many entertainment venues and multi-function halls use the above strategy: Retain stereo capability in the equipment configuration but use it in mono during operation. Since design requirements for these venues aren't uniform, the amplification format should be flexible.
For example, use a combination of stereo and mono: Apply stereo reinforcement in prime seating/dance floor areas, and mono elsewhere. The core principle: Ensure all listening areas receive the complete program. Avoid excessive speakers or irregular placement causing destructive wave interference.
Surround Sound
Builds upon standard stereo, enhancing spatial sense and image solidity. It's an advanced format installed in some new cinemas and theaters domestically.
5. Equipment Selection
Speakers
Speakers are the voice of the entire system, hence the primary consideration. Speaker selection starts with sensitivity and rated power to determine power per source. Use speaker directivity to analyze and control the hall's sound field, determine each speaker's position, input impedance, and input power. Calculate matching power between speakers and amplifiers.
Power Amplifiers
To ensure overall sound quality, amplifiers need sufficient power headroom and long-term stability. Selected amplifiers should have robust technical measures for efficiency, low distortion, short-circuit/no-load protection, and thermal management.
Mixers & Other Equipment
The mixer is the heart of the sound system. It must have good electrical performance, stable operation, flat frequency response, minimal harmonic distortion. Mixers vary greatly in functionality; choose based on the system's requirements for input channels and output groups.
Furthermore, based on the hall's acoustics, select appropriate EQs, delays, reverbs, compressors/limiters, frequency shifters, etc., to form a normal, stable, and reliable sound reinforcement system.
Source Equipment
Source components include FM/AM broadcast reception/relay, record (including CD) and tape playback equipment. Since source levels are low, all components/devices must ensure high sensitivity, high S/N ratio, low distortion, and high reliability.
Microphone Selection
Microphones are the first 'entry point' of the system. Natural sound converted to voltage by the mic is amplified thousands of times by the mixer and power amp before reaching the speakers.
Microphone quality directly impacts system quality; its characteristics directly affect pickup and reproduction; placement directly affects system gain before feedback; signal connection directly affects S/N ratio. Correct microphone use is key to the entire audio system performing well.
Microphone selection must match the acoustic environment and sound source. Base choices on the overall system requirements, application scenario, sound source characteristics, mic specifications, and hall features.
6. Conduit Design
Fixed-installation systems typically run mic and instrument cables from the stage to the control room, and amplifier outputs to speakers. These cables should be run in conduit.
Metal Conduit Installation
This refers to running mic input lines and speaker output lines outside the control room. Although shielded cable is used, for permanent installation, whether concealed or surface-mounted, metal conduit is preferred.
Benefits of metal conduit:
① Protects cables from damage;
② Provides excellent shielding against electromagnetic interference;
③ Allows conduit installation first, cable pulling later—very convenient—and easier cable replacement. In new/renovated halls, conduit design is crucial for undistorted signal transmission.
Conduit Design Key Points
To reduce induced noise, mic input lines often use twin-core shielded cable and MUST be run in metal conduit. For exceptionally long runs, avoid proximity and parallel routing with power cables.
Since mic positions may change, pre-install multiple junction boxes during design. Equip each with XLR sockets. Position them appropriately (e.g., inside stage side walls, under stage front/band floor, under VIP/referee stands). Pre-wire all junction boxes for easy access.
For speaker cables, to ensure power delivery and damping match between amp and speaker, simply choose sufficiently thick wire run in conduit. For the main PA, use a ring ('daisy-chain') wiring method per group for reliability. This ensures the entire main PA keeps working even if any point in a group breaks. Once control room location, mic socket boxes, and speaker positions are fixed, design an economical and rational conduit layout avoiding strong interference, based on the building structure. Produce a construction plan drawing.
7. Conduit Installation Process
Note these points during conduit installation:
(1) Run lighting and audio cables in separate conduits, maintaining at least 1m spacing when parallel. Maintain at least 0.5m spacing when crossing perpendicularly. Avoid parallel runs if possible.
(2) When pulling 3+ cables through one conduit, total conductor cross-section shouldn't exceed 40% of the conduit's internal area. For two cables, conduit area should be >1.2 times cable cross-section.
(3) For ease of pulling: Max length 50m for straight runs; 30m for 1-2 bends; 15m for 3-4 bends. Exceeding these requires junction boxes for segmented pulling.
(4) Conduit MUST be grounded to prevent interference. All conduit and junction boxes must form a continuous, grounded system—this is vital.