Apple Performa 6400/180 - Manual (Page 21)

Basics Subwoofer Balance Control - 19
Adjust the subwoofer
balance using the subwoofer
balance control. The
subwoofer balance control
only works with external
speakers attached. To
increase or decrease the
bass coming from the
subwoofer in relation to the
sound coming from the
external speakers, adjust
the subwoofer balance
control.
Subwoofer Balance Control