at beginning, thanks for everybody for sharing knowledge.
my case like that:

(side A)<<--------2KM--------------(PA1 Main Control PA2)--------------2KM------------>>(side B)

1-I have fixed two High Power PA Amplifiers with 1000 WATTS for each.
2-I have used 1.5mm wiring to connect PA Horn Speakers.
3-I have connect 130 PA Horn Speakers at each side from center to side A and side B.
4-The Horn Speaker setting at 5WATTS.
5-The PA Amplifiers Speaker Outputs settings at 100V
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PA Specification
1-The PA Amplifiers Speaker Outputs 2ohm & 4ohm, 70V & 100V
2-The PA Amplifiers Input Channels
8 Mic 0.8mV/4.7k ohm, 3 Aux 100mV/50k ohm
1 Aux 250mV/50k ohm
1 Line 1V/50k ohm
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The Problem:-
above 1KM from the center, the sound becomes boor.

how to solve this problem? and make the sound reach the full 2 km at each side.

At the end Thanks again