An apparatus for generating an output signal having at least two output channels from an input signal having at least two input channels. The apparatus comprises an ambient/direct decomposer (110; 210; 310; 410; 610), an ambient modification unit (120; 220; 320; 420) and a combination unit (130; 230; 330; 430). The ambient/direct decomposer (110; 210; 310; 410; 610) is adapted to decompose at least two input channels of the input signal such that each one of the at least two input channels is decomposed into a signal of a first signal group and into a signal of a second signal group. The ambient modification unit (120; 220; 320, 420) is adapted to modify a signal of the ambient signal group or a signal derived from a signal of the ambient signal group to obtain a modified signal as a first output channel. The combination unit (130; 230; 330; 430) is adapted to combine a signal of the ambient signal group or a signal derived from a signal of the ambient signal group and a signal of the direct, signal group or a signal derived from a signal of the direct signal group as a second output channel.