Speaker System

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					                          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).

				
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posted:2/9/2012
language:English
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