Bonjour!
Add 'A.SETUP' to the list on the Beo4. After you have added it to the Beo4 list, press list until 'A.SETUP' appears, press 'GO' and then press list agin and 'BASS', 'Trebble' and 'Loudnss' can be accessed. Once the desired parameter is shown on the Beo4 display, press 'GO' and then use volume up and down button to adjust the parameter. However, the settings made this way will not be stored after the beomaster is put to standby. I do not know how to store since there seems to be no 'STORE' command on the Beo4 like there is on the Beolink 1000.