Subaru 2001 Legacy Owner's Manual page 220

Choose desired volume level for each mode by turning the volume
control dial. The control function returns to volume control mode after
about 5 seconds.
To change control modes: Each brief press of the "AUDIO" button
5
changes control modes in the following sequence starting from vol-
ume control mode. (When the radio is first turned on, the control mode
is in the volume control.)
Volume
(VOL)
The "AUDIO" button
modes:
Display Control mode
BAS Bass control
TRE Treble control
FAD Fader control
BAL Balance control
VOL Volume control
5-34
Bass Treble
(BAS) (TRE)
5
is used for selecting the following control
Turn counterclockwise
For less bass
For less treble
To increase rear speaker
volume and decrease front
speaker volume
To increase left speaker
volume and decrease right
speaker volume
For less volume
Fader Balance
(FAD) (BAL)
Turn clockwise
For more bass
For more treble
To increase front speaker
volume and decrease rear
speaker volume
To increase right speaker
volume and decrease left
speaker volume
For more volume
HB5036BA