1. Multi-channel audio decoder for processing a parametric representation, wherein the parametric representation is comprising information on one or more spatial parameters describing spatial properties of a multi-channel signal and a stereo parameter describing spatial properties of a stereo downmix of the multi-channel signal, wherein the information on the one or more spatial parameters and the stereo parameter, when combined using a combination rule, results in one or more spatial parameters, the decoder comprising: a parameter reconstructor for combining the stereo parameter and the information on the one or more spatial parameters using the combination rule to obtain the one or more spatial parameters.