CEA CEA Live Sound & Event Production 2 — Questions and Answers
Question 1: What is a 'stage plot' in live event production?
- A diagram showing speaker placement throughout a venue
- A scale drawing showing the positions of musicians, equipment, and monitors on stage (Correct answer)
- The FOH engineer's channel layout on the mixing console
- A document listing acceptable sound pressure levels for the venue
Correct answer: A scale drawing showing the positions of musicians, equipment, and monitors on stage
A stage plot is a diagram provided by the performing act that shows where each performer and piece of equipment will be positioned on stage to guide the crew's setup.
Question 2: What is 'time alignment' in a multi-speaker PA system?
- Synchronizing the MIDI clock between instruments on stage
- Delaying certain speaker clusters so that sound from all sources arrives at the listener simultaneously (Correct answer)
- Setting the compressor attack and release to match the tempo of the music
- Aligning the phase of subwoofers with the main PA using polarity inversion
Correct answer: Delaying certain speaker clusters so that sound from all sources arrives at the listener simultaneously
Time alignment uses delay to compensate for the physical distance differences between speakers, ensuring that sound from all parts of the system arrives at the listener at the same time to prevent comb filtering and imaging issues.
Question 3: What is an 'input list' (or 'patch list') in a live sound context?
- A list of all wireless frequencies used at an event
- A numbered list of every audio source, its microphone or DI type, and its assigned console channel (Correct answer)
- A troubleshooting guide for common live sound problems
- The amplifier channel assignments for the PA system
Correct answer: A numbered list of every audio source, its microphone or DI type, and its assigned console channel
An input list is a document that catalogs every audio input for a show, specifying the source, microphone/DI type, stand requirements, and console channel assignment.
Question 4: What is 'subwoofer cardioid configuration' in a live PA system?
- A method of using directional cardioid microphones to reduce feedback from subs
- An arrangement of subwoofers using delay and polarity inversion to reduce rear-firing energy (Correct answer)
- A crossover technique that limits sub frequencies to only the center speaker cluster
- A filter that prevents subwoofer frequencies from entering monitor mixes
Correct answer: An arrangement of subwoofers using delay and polarity inversion to reduce rear-firing energy
Cardioid subwoofer arrays are created by combining forward-facing and rear-facing delayed subs to cancel low-frequency energy behind the array while reinforcing it in front.
Question 5: What does 'SPL' stand for and how is it measured in live sound?
- Speaker Power Load — measured in watts delivered to the speaker
- Sound Pressure Level — measured in decibels using a calibrated sound level meter (Correct answer)
- Signal Processing Latency — measured in milliseconds at the console output
- Stage Power Limit — measured in amperes from the venue's electrical service
Correct answer: Sound Pressure Level — measured in decibels using a calibrated sound level meter
Sound Pressure Level (SPL) is the acoustic pressure of sound relative to a reference, measured in dB using a calibrated SPL meter, often to comply with venue noise ordinances.
Question 6: What is the purpose of a DI (Direct Injection) box in a live sound setup?
- To increase the output level of a condenser microphone
- To convert a high-impedance unbalanced instrument signal to a low-impedance balanced signal suitable for a mixing console (Correct answer)
- To eliminate radio frequency interference from wireless systems
- To provide phantom power to dynamic microphones
Correct answer: To convert a high-impedance unbalanced instrument signal to a low-impedance balanced signal suitable for a mixing console
A DI box matches impedance and converts an unbalanced high-impedance source (like a guitar or keyboard) to a balanced low-impedance signal that can travel long cable runs to the console without noise.
CEA CEA Live Sound & Event Production 2
What is a 'stage plot' in live event production?