My CP-AS1080 Active subwoofer is distorting when I turn the level up higher than zero
If you are conected to the High Level input of the CP-AS1080 you must set the level to zero and control the volume from the source/head unit. Overdriving the unit will damage the woofer and /or the internal amplifier.
if you are connected via RCA cables (low level) you may have a sub level control on the source/head unit that could be set incorrectly or try level matching the CP-AS1080 to get better control over the subwoofer. see Gain Level Matching