SPEAKER SYSTEM SPEAKER SYSTEM Speaker system in sound reinforcement are divide into several functions: 1. Front of House (FOH) – speakers facing to the audience 2. Foldback Monitor – speakers at the stage area for the people on the stage i.e performer and the band. 3. Monitor – used for sound mixing personel to monitor the system SPEAKER SYSTEM SPEAKER SYSTEM FOH Speaker FOH speakers system requirement are normally as follows: 1. Purpose of function (speech or musical) 2. Coverage area 3. Number of audience SPEAKER SYSTEM SPEAKER SYSTEM FOH Speaker For speech purpose sound reinforcement system, several numbers of full range speakers are good enough. For musical purpose sound reinforcement system, combination of full range speakers and subwoofer are required. Based on required SPL and coverage area, the number of speakers and amplifier can be determined. SPEAKER SYSTEM SPEAKER SYSTEM FOH Speaker Two type of FOH speakers arrangement: Stack – speakers are stacked on top each other Line Array – a number of speakers arrange in vertical array and suspended to ceiling or truss SPEAKER SYSTEM SPEAKER SYSTEM FOH Speaker - SPL To get the high SPL, multiple speakers are required. For the same power amplifier rating, two times the number of speakers will add the the SPL by 3 dB. To add 3 dB sound level will require two times power handling. Two times the distance will reduce the SPL by 6 dB. dB SPL = Max SPL + (20 x Log (distance1/distance2)) A speaker with 96 dB SPL sensitivity and drive with 500 Watts amplifier will produce about 123 dB sound level at 1 meter. At 2 meter, the SPL is droped by 6 dB ie 117 dB. SPEAKER SYSTEM SPEAKER SYSTEM Reference table for SPL and required power for speaker with 96 dB SPL sensitivity with 123 dB maximum SPL. dB SPL @ 1 meter Amplifier Power (Watts) 96 1 99 2 102 4 105 8 108 16 111 32 114 64 117 128 120 256 123 512 SPEAKER SYSTEM SPEAKER SYSTEM Reference table for SPL drop with distance for a speaker with 96 dB SPL sensitivity with 123 dB maximum SPL. Distance (meter) SPL (dB) 1 123 2 117 4 111 8 105 16 99 32 93 64 87 128 81 SPEAKER SYSTEM SPEAKER SYSTEM Reference table for SPL increase by adding speaker for a speaker with 96 dB SPL sensitivity with 1 Watt power each speaker at 1 meter distance. No. of Speaker SPL (dB) 1 96 2 99 4 102 8 105 16 108 32 111 SPEAKER SYSTEM SPEAKER SYSTEM Reference table for SPL level by 4 speakers producing 120 dB SPL each (total 126 dB SPL) with distance. Distance (meter) dB (SPL) 1 126 2 120 4 114 8 108 16 102 32 98 SPEAKER SYSTEM SPEAKER SYSTEM Foldback Monitoring System Foldback monitoring system is sub-system of the of a sound reinforcement system. The signal output is independently from the signal that fed to the FOH speakers. For small or medium system, the auxiliary output of the FOH mixer can be used for foldback monitoring. For medium and large system, a separate mixer console normally used for the the foldback monitoring. The foldback monitoring system shall be able to send the output for different sound for each speaker. SPEAKER SYSTEM SPEAKER SYSTEM Foldback Monitoring System The foldback monitor speaker is designed in wedge-shaped so it can be located horizontally for the speaker axis facing upward to the musician and performer. As the monitor speaker sit horizontally, it is good to have wider vertical dispersion and narrow horizontal dispersion angle. Care should be taken for the positioning of the monitor speaker where a number of microphone are located at the stage. SPEAKER SYSTEM SPEAKER SYSTEM Foldback Monitoring System For recording studio, the foldback monitor are not using the speaker but through the headphone. SPEAKER SYSTEM SPEAKER SYSTEM Monitoring System There is one more monitoring system for the sound reinforcement system, monitor for the sound man. Mixer console has an output for the monitoring through the built-in headphone amplifier. Beside that, a pair of monitoring output available to be connected to the monitor speaker (through amplifier or if not, to the active monitor speaker).