Can I adjust the bass and treble adjustment buttons without harming the speakers or the unit? (see picture below) This unit is a STR-DH130. The range is from -15dB to +15db. If I had +12dB does that mean I have to have -12db treble? Also, could I have +15dB bass and +15dB treble at the same time? (or vice avers (-15dB bass and -15dB treble?) Thank you for the answers, I will try to respond if I have another question with comments or posting an answer on my question. Please respond to my replies, thank you!