Don't mean to be condescending but you and some others perceive that it does.
The only way of being sure is a properly staged double blind listening test. These are difficult but not impossible to arrange. Just changing a power cord is not hard or slow, but with powered speakers is the residue of 'old' electricity remaining in the speakers' capacitors will not allow a clean quick changeover.
Just for the record, have you experienced sound differences from changing the power cord to a turntable motor?