Sensitivity rating for your center speaker is 86db while the rating for your surrounds are 81db. Totally makes sense that you'd have to adjust the channel levels higher for the surrounds.
Output Sound Pressure Level -
Front 85 dB/W/m
Center 86 dB/W/m
Surround 81 dB/W/m
Surround Back 81 dB/W/m
Output Sound Pressure Level -
Front 85 dB/W/m
Center 86 dB/W/m
Surround 81 dB/W/m
Surround Back 81 dB/W/m














