Volvo 2004 V70R Operation And Care Manual page 107

Adjust the bass by pressing the button to extend the control and turning it to the left (less bass) or to the right (more
bass). A "detent" indicates "equalized" bass. Press the button back in when you have made the adjustment.
Treble
Adjust the treble by pressing the button to extend the control, pulling it out as far as possible, and then turning it to the
left (less treble) or to the right (more treble). A "detent" indicates "equalized" treble. Press the button back in when you
have made the adjustment.
Band selector
Turn "SOURCE" knob to select FM or AM. The station and band are displayed. You can also select cassette deck,
CD, or optional CD changer with this knob.
Active sound control (ASC)
The ASC (Active Sound Control) automatically adapts volume to vehicle speed.
Press the ASC button (HU-613) for several seconds to switch this function ON or OFF. This function is included in
the Advanced User Mode on the HU-803 equipped with this feature.
"ASC ON" or "ASC OFF" will be shown in the display for several seconds.
pg. 157 Audio systems HU-613/HU-803
Fader - Balance front/rear
Adjust front/rear speaker balance by pressing the button to extend the control and turning it to the left (more sound
from the rear speakers) or to the right (more sound from the front speakers). A "detent" indicates "equalized" balance.
Press the button back in when you have made the adjustment.
Balance right/left
Adjust left/right speaker balance by pressing the button to extend the control, pulling it out as far as possible and then
turning it to the left (more sound from the left speakers) or to the right (more sound from the right speakers). A
"detent" indicates "equalized" balance. Press the button back in when you have made the adjustment.