An apparatus for generating two or more audio output channels from three or more audio input channels, wherein the apparatus comprises: a receiving interface for receiving the three or more audio input channels and for receiving side information, and a downmixer for downmixing the three or more audio input channels depending on the side information using a weight for each audio input channel to obtain the two or more audio output channels, wherein the number of the audio output channels is smaller than the number of the audio input channels, wherein the side information indicates a characteristic of at least one of the three or more audio input channels, or a characteristic of one or more sound waves recorded within the one or more audio input channels, or a characteristic of one or more sound sources which emitted one or more sound waves recorded within the one or more audio input channels, and wherein the downmixer is configured to determine the weight for each audio input channel depending on the side information, wherein the apparatus is configured to feed each of the two or more audio output channels into a loudspeaker of a group of two or more loudspeakers, wherein the downmixer is configured to downmix the three or more audio input channels depending on each assumed loudspeaker position of a first group of three or more assumed loudspeaker positions and depending on each actual loudspeaker position of a second group of two or more actual loudspeaker positions to obtain the two or more audio output channels, wherein each actual loudspeaker position of the second group of two or more actual loudspeaker positions indicates a position of a loudspeaker of the group of two or more loudspeakers, wherein each audio input channel of the three or more audio input channels is assigned to an assumed loudspeaker position of the first group of three or more assumed loudspeaker positions, wherein each audio output channel of the two or more audio output channels is assigned to an actual loudspeaker position of the second group of two or more actual loudspeaker positions, wherein the downmixer is configured to generate each audio output channel of the two or more audio output channels depending on at least two of the three or more audio input channels, depending on the assumed loudspeaker position of each of said at least two of the three or more audio input channels and depending on the actual loudspeaker position of said audio output channel, characterised in that the side information comprises an amount of ambience of each of the three or more audio input channels, wherein the downmixer is configured to downmix the three or more audio input channels depending on-the amount of ambience of each of the three or more audio input channels to obtain the two or more audio output channels. a receiving interface for receiving the three or more audio input channels and for receiving side information, and a downmixer for downmixing the three or more audio input channels depending on the side information using a weight for each audio input channel to obtain the two or more audio output channels, wherein the number of the audio output channels is smaller than the number of the audio input channels, wherein the side information indicates a characteristic of at least one of the three or more audio input channels, or a characteristic of one or more sound waves recorded within the one or more audio input channels, or a characteristic of one or more sound sources which emitted one or more sound waves recorded within the one or more audio input channels, and wherein the downmixer is configured to determine the weight for each audio input channel depending on the side information, wherein the apparatus is configured to feed each of the two or more audio output channels into a loudspeaker of a group of two or more loudspeakers, wherein the downmixer is configured to downmix the three or more audio input channels depending on each assumed loudspeaker position of a first group of three or more assumed loudspeaker positions and depending on each actual loudspeaker position of a second group of two or more actual loudspeaker positions to obtain the two or more audio output channels, wherein each actual loudspeaker position of the second group of two or more actual loudspeaker positions indicates a position of a loudspeaker of the group of two or more loudspeakers, wherein each audio input channel of the three or more audio input channels is assigned to an assumed loudspeaker position of the first group of three or more assumed loudspeaker positions, wherein each audio output channel of the two or more audio output channels is assigned to an actual loudspeaker position of the second group of two or more actual loudspeaker positions, wherein the downmixer is configured to generate each audio output channel of the two or more audio output channels depending on at least two of the three or more audio input channels, depending on the assumed loudspeaker position of each of said at least two of the three or more audio input channels and depending on the actual loudspeaker position of said audio output channel, characterised in that the side information comprises an amount of ambience of each of the three or more audio input channels, wherein the downmixer is configured to downmix the three or more audio input channels depending on-the amount of ambience of each of the three or more audio input channels to obtain the two or more audio output channels.