How to Tune a Live Sound Reinforcement System
Facing such a complex and large-scale project, simplifying its description is nearly impossible. Today, we will briefly outline some fundamental steps within the two main parts of traditional analog system tuning and sound tuning for live sound reinforcement systems. We hope this aids enthusiasts in the field of sound reinforcement. Corrections and additions are welcome via comments.
Regarding System Tuning
Step 1: Initial System Level Calibration
1. Line Check
Carefully inspect all connections according to the system wiring diagram, ensuring all lines function correctly.
2. Device Initial State Setup
Set amplifier inputs to minimum. Set all input/output knobs on peripheral devices to the 0dB position or midpoint. Power on devices sequentially from front-end to back-end (amplifiers last). After confirming all devices power on correctly, power on the amplifiers.
3. Preliminary System Status Check
Gradually increase the amplifier gain control. Play a familiar CD, adjusting the mixer input level to a normal position. Slowly raise the mixer fader and listen if the sound from the speakers is normal and undistorted. If not, power down immediately and check.
4. Speaker & System Polarity Check
Once basic system function is confirmed, power on all devices with amplifier levels set to maximum. Lower the mixer output fader. Connect a phase tester generator to a mixer input channel. Power on the generator and adjust its output gain and mixer input gain until the mixer meter reads 0dB. Slowly raise the mixer output fader until the "thump" sound from the speakers is sufficiently loud (insufficient loudness may yield inaccurate results). Use the phase tester detector to check each speaker's polarity, comparing it to the speaker manual. For accuracy, test speakers individually by muting others. If incorrect, check for reversed speaker cables or system connections and correct.
5. Phase Alignment
When using subwoofers and full-range speakers together, crossover interference or differing time delays due to placement can cause phase issues, necessitating phase alignment. Connect a pink noise generator to a mixer input channel and set its level normally. Place the phase tester microphone centrally, forming an equilateral triangle with the speakers. Raise the mixer output fader. Check the spectrum analyzer screen for significant dips (nulls) around the crossover frequency between full-range and subwoofers. If dips exist and cannot be corrected by boosting the corresponding EQ band, a phase problem exists. Phase issues directly degrade sound quality and cannot be fixed with EQ. Resolve them by adjusting the crossover phase angle or delay time between speaker groups. Monitor the spectrum analyzer: first adjust the low-frequency crossover phase angle for improvement. Once optimized, adjust delay times based on placement (e.g., delay subs if closer to seating). Aim to minimize phase cancellation, smoothing the frequency response curve.
6. Frequency Equalization
Following phase alignment, tune the system's frequency response. Place the spectrum analyzer's measurement microphone at a listener position. Play pink noise and observe the spectrum display. Use the system EQ to correct deficiencies. Repeat this process at multiple positions within the listening area, iteratively adjusting the EQ for the flattest possible response across the area.
7. Dynamic Processor Calibration
Compressors/Limiters are typical dynamic processors. When connected in series within the system chain, they primarily serve as protection, utilizing their limiting function. While setup varies, one common method involves bypassing the limiter initially, setting input/output gain to 0dB, and ratio to "∞" (infinity:1). Send pink noise from the mixer, gradually increasing the level until the amplifier's input clip indicator lights. Engage the limiter and adjust its threshold control until the clip indicator turns off. Then, increase the mixer output by 6dB (or until its output meter reads +6dB). Fine-tune the threshold slightly until the amplifier clip indicator just begins to flicker. This completes the system level calibration. Sound tonality adjustments and effects processing (including effects units, exciters, etc.) fall under the sound engineer's purview, typically handled by audio company technicians in professional installations.
Step 2: Preventing Feedback & Vocal Microphone Toning
1. Monitor System
Calibrate one microphone level as per Step 1, bypassing any mixer channel EQ. Set the channel fader to 0dB (assuming monitor signals are post-fader auxiliary sends). Place the microphone at a key stage position. Open the monitor output master (AUX) and gradually increase its level until feedback occurs in a specific frequency band. Fine-tune the AUX send level to stabilize the feedback at a constant volume. Then, adjust the corresponding band on the monitor system EQ to eliminate that feedback frequency. Continue increasing the level until another feedback band emerges, and repeat the EQ adjustment process. Proceed incrementally until the mixer output fader or AUX send reaches its normal position (e.g., 0dB) without feedback. Return the mixer fader to its starting position. This method identifies resonant feedback points inherent to the room. Then, slightly reduce the microphone channel gain. Have someone speak into the microphone on stage and gradually increase the mic level to normal. If feedback persists, eliminate it using the system EQ.
Key Points: Control levels carefully to maintain stable feedback for accurate identification. Proceed slowly; rushing prevents identifying individual points. Rooms typically have 5-6 resonant points. Excessive feedback points suggest suboptimal speaker placement.
2. Main PA System
After tuning the monitor system feedback points, repeat the process for the main PA system. For stereo PA, mute one channel first. Raise the mixer input fader and gradually increase volume to find feedback points. Tune one channel, then mute it and tune the other. After tuning both, activate both channels together to check for any remaining feedback points and eliminate them using the main system EQ.
Regarding Sound Tuning
After resolving feedback, proceed with sound toning.
1. Vocal Microphones
Use a high-quality reference microphone. Adjust the microphone input channel EQ on the mixer to match the reference mic's tonality as closely as possible. This baseline generally satisfies most vocalists. Have the vocalist test the mic and make minor EQ tweaks per their preference.
2. Adding Effects
Once the dry vocal tone is satisfactory, add reverb effects if desired. Select an appropriate reverb type on the effects unit. Enable the corresponding AUX send on the mixer. Simultaneously adjust the effects unit input gain and the mixer auxiliary send level. Have someone speak into the mic; monitor the signal sent to the effects unit, aiming for around 0dB. Set the effects unit mix ratio to 100%. Gradually increase the effects unit output level, monitoring the signal returning to the mixer for normal levels. Once confirmed, set the effects level according to the vocalist's preference.
Adding effects can introduce new feedback points, often first appearing in the low frequencies. Effects returns are typically routed to mixer line inputs. Use the EQ on this input channel to eliminate any new feedback.
This completes the fundamental sound system tuning process.
Recent technological advancements have brought forth digital networked and analog control products, freeing sound engineers from mountains of cables and equipment. Empowered by sophisticated tools, sound engineers increasingly focus on artistic and sensory aspects, leveraging rational technology and experience to deliver high-quality live performances.
Regarding System Tuning
Step 1: Initial System Level Calibration
1. Line Check
Carefully inspect all connections according to the system wiring diagram, ensuring all lines function correctly.
2. Device Initial State Setup
Set amplifier inputs to minimum. Set all input/output knobs on peripheral devices to the 0dB position or midpoint. Power on devices sequentially from front-end to back-end (amplifiers last). After confirming all devices power on correctly, power on the amplifiers.
3. Preliminary System Status Check
Gradually increase the amplifier gain control. Play a familiar CD, adjusting the mixer input level to a normal position. Slowly raise the mixer fader and listen if the sound from the speakers is normal and undistorted. If not, power down immediately and check.
4. Speaker & System Polarity Check
Once basic system function is confirmed, power on all devices with amplifier levels set to maximum. Lower the mixer output fader. Connect a phase tester generator to a mixer input channel. Power on the generator and adjust its output gain and mixer input gain until the mixer meter reads 0dB. Slowly raise the mixer output fader until the "thump" sound from the speakers is sufficiently loud (insufficient loudness may yield inaccurate results). Use the phase tester detector to check each speaker's polarity, comparing it to the speaker manual. For accuracy, test speakers individually by muting others. If incorrect, check for reversed speaker cables or system connections and correct.
5. Phase Alignment
When using subwoofers and full-range speakers together, crossover interference or differing time delays due to placement can cause phase issues, necessitating phase alignment. Connect a pink noise generator to a mixer input channel and set its level normally. Place the phase tester microphone centrally, forming an equilateral triangle with the speakers. Raise the mixer output fader. Check the spectrum analyzer screen for significant dips (nulls) around the crossover frequency between full-range and subwoofers. If dips exist and cannot be corrected by boosting the corresponding EQ band, a phase problem exists. Phase issues directly degrade sound quality and cannot be fixed with EQ. Resolve them by adjusting the crossover phase angle or delay time between speaker groups. Monitor the spectrum analyzer: first adjust the low-frequency crossover phase angle for improvement. Once optimized, adjust delay times based on placement (e.g., delay subs if closer to seating). Aim to minimize phase cancellation, smoothing the frequency response curve.
6. Frequency Equalization
Following phase alignment, tune the system's frequency response. Place the spectrum analyzer's measurement microphone at a listener position. Play pink noise and observe the spectrum display. Use the system EQ to correct deficiencies. Repeat this process at multiple positions within the listening area, iteratively adjusting the EQ for the flattest possible response across the area.
7. Dynamic Processor Calibration
Compressors/Limiters are typical dynamic processors. When connected in series within the system chain, they primarily serve as protection, utilizing their limiting function. While setup varies, one common method involves bypassing the limiter initially, setting input/output gain to 0dB, and ratio to "∞" (infinity:1). Send pink noise from the mixer, gradually increasing the level until the amplifier's input clip indicator lights. Engage the limiter and adjust its threshold control until the clip indicator turns off. Then, increase the mixer output by 6dB (or until its output meter reads +6dB). Fine-tune the threshold slightly until the amplifier clip indicator just begins to flicker. This completes the system level calibration. Sound tonality adjustments and effects processing (including effects units, exciters, etc.) fall under the sound engineer's purview, typically handled by audio company technicians in professional installations.
Step 2: Preventing Feedback & Vocal Microphone Toning
1. Monitor System
Calibrate one microphone level as per Step 1, bypassing any mixer channel EQ. Set the channel fader to 0dB (assuming monitor signals are post-fader auxiliary sends). Place the microphone at a key stage position. Open the monitor output master (AUX) and gradually increase its level until feedback occurs in a specific frequency band. Fine-tune the AUX send level to stabilize the feedback at a constant volume. Then, adjust the corresponding band on the monitor system EQ to eliminate that feedback frequency. Continue increasing the level until another feedback band emerges, and repeat the EQ adjustment process. Proceed incrementally until the mixer output fader or AUX send reaches its normal position (e.g., 0dB) without feedback. Return the mixer fader to its starting position. This method identifies resonant feedback points inherent to the room. Then, slightly reduce the microphone channel gain. Have someone speak into the microphone on stage and gradually increase the mic level to normal. If feedback persists, eliminate it using the system EQ.
Key Points: Control levels carefully to maintain stable feedback for accurate identification. Proceed slowly; rushing prevents identifying individual points. Rooms typically have 5-6 resonant points. Excessive feedback points suggest suboptimal speaker placement.
2. Main PA System
After tuning the monitor system feedback points, repeat the process for the main PA system. For stereo PA, mute one channel first. Raise the mixer input fader and gradually increase volume to find feedback points. Tune one channel, then mute it and tune the other. After tuning both, activate both channels together to check for any remaining feedback points and eliminate them using the main system EQ.
Regarding Sound Tuning
After resolving feedback, proceed with sound toning.
1. Vocal Microphones
Use a high-quality reference microphone. Adjust the microphone input channel EQ on the mixer to match the reference mic's tonality as closely as possible. This baseline generally satisfies most vocalists. Have the vocalist test the mic and make minor EQ tweaks per their preference.
2. Adding Effects
Once the dry vocal tone is satisfactory, add reverb effects if desired. Select an appropriate reverb type on the effects unit. Enable the corresponding AUX send on the mixer. Simultaneously adjust the effects unit input gain and the mixer auxiliary send level. Have someone speak into the mic; monitor the signal sent to the effects unit, aiming for around 0dB. Set the effects unit mix ratio to 100%. Gradually increase the effects unit output level, monitoring the signal returning to the mixer for normal levels. Once confirmed, set the effects level according to the vocalist's preference.
Adding effects can introduce new feedback points, often first appearing in the low frequencies. Effects returns are typically routed to mixer line inputs. Use the EQ on this input channel to eliminate any new feedback.
This completes the fundamental sound system tuning process.
Recent technological advancements have brought forth digital networked and analog control products, freeing sound engineers from mountains of cables and equipment. Empowered by sophisticated tools, sound engineers increasingly focus on artistic and sensory aspects, leveraging rational technology and experience to deliver high-quality live performances.