Lowrance SonicHub Marine Audio Server Mode D'emploi page 13

Audio Outputs
Your unit has three audio outputs; two allotted for
speakers (front and rear) and one with amplifier and
sub-woofer outputs.
Volume, balance and fade settings are the same for
each output.
Audio Output 1
Audio Output 2
Audio Output 3
SonicHub Audio Outputs
Front speakers
Rear speakers (not included)
Amplifier output; sub-woofer output
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Settings