LG S90QY Owner's Manual page 11

Attaching the ferrite core (optional)
A ferrite core may not be provided depending on national standards.
Attaching the ferrite core to the speaker cables
Attach the ferrite core to the cables to reduce radio noise.
a Pull Part [a] to open the ferrite core.
b Wind the wireless receiver's speaker cables twice around the ferrite core. A distance of about 18 cm (7.1
inch) is required between the wireless receiver and the ferrite core.
c Close the ferrite core until you hear a click.
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