An apparatus adapted to provide a current loudspeaker-enclosure-microphone system description ( H̃ ( n)) of a loudspeaker-enclosure-microphone system, wherein the loudspeaker-enclosure-microphone system comprises a plurality of loudspeakers (110; 210; 610) and a plurality of microphones (120; 220; 620), and wherein the apparatus comprises: a first transformation unit (130; 330; 630) for generating a plurality of wave-domain loudspeaker audio signals ( x̃ 0 ( n),... x̃ l ( n),..., x̃ N L -1 ( n)), wherein the first transformation unit (130; 330; 630) is configured to generate each of the wave-domain loudspeaker audio signals ( x̃ 0 ( n),... x̃ l ( n),..., x̃ N L -1 ( n)) based on a plurality of time-domain loudspeaker audio signals ( x 0 ( n),..., x λ ( n),..., x N L -1 ( n)) and based on one or more of a plurality of loudspeaker-signal-transformation values ( l; l'), a second transformation unit (140; 340; 640) for generating a plurality of wave-domain microphone audio signals ( d̃ 0 ( n),... d̃ m ( n),..., d̃ N M -1 ( n)), wherein the second transformation unit (140; 340; 640) is configured to generate each of the wave-domain microphone audio signals ( d̃ 0 ( n),... d̃ m ( n),..., d̃ N M -1 ( n)) based on a plurality of time-domain microphone audio signals ( d 0 ( n),..., d μ ( n),..., d N M -1 ( n)) and based on one or more of a plurality of microphone-signal-transformation values ( m, m'), and a system description generator for generating the current loudspeaker-enclosure-microphone system description based the plurality of wave-domain loudspeaker audio signals ( x̃ 0 ( n),... x̃ l ( n),..., x̃ N L -1 ( n)), and based on the plurality of wave-domain microphone audio signals ( d̃ 0 ( n),... d̃ m ( n),..., d̃ N M -1 ( n)), wherein the system description generator is configured to generate the loudspeaker-enclosure-microphone system description based on a plurality of coupling values, wherein each of the plurality of coupling values is assigned to one of a plurality of wave-domain pairs, each of the plurality of wave-domain pairs being a pair of one of the plurality of loudspeaker-signal-transformation values ( l; l') and one of the plurality of microphone-signal-transformation values ( m; m'), wherein the system description generator is configured to determine each coupling value assigned to a wave-domain pair of the plurality of wave-domain pairs by determining for said wave-domain pair at least one relation indicator indicating a relation between said one of the loudspeaker-signal-transformation values of said wave-domain pair and said one of the microphone-signal-transformation values of said wave-domain pair to generate the loudspeaker-enclosure-microphone system description. a first transformation unit (130; 330; 630) for generating a plurality of wave-domain loudspeaker audio signals ( x̃ 0 ( n),... x̃ l ( n),..., x̃ N L -1 ( n)), wherein the first transformation unit (130; 330; 630) is configured to generate each of the wave-domain loudspeaker audio signals ( x̃ 0 ( n),... x̃ l ( n),..., x̃ N L -1 ( n)) based on a plurality of time-domain loudspeaker audio signals ( x 0 ( n),..., x λ ( n),..., x N L -1 ( n)) and based on one or more of a plurality of loudspeaker-signal-transformation values ( l; l'), a second transformation unit (140; 340; 640) for generating a plurality of wave-domain microphone audio signals ( d̃ 0 ( n),... d̃ m ( n),..., d̃ N M -1 ( n)), wherein the second transformation unit (140; 340; 640) is configured to generate each of the wave-domain microphone audio signals ( d̃ 0 ( n),... d̃ m ( n),..., d̃ N M -1 ( n)) based on a plurality of time-domain microphone audio signals ( d 0 ( n),..., d μ ( n),..., d N M -1 ( n)) and based on one or more of a plurality of microphone-signal-transformation values ( m, m'), and a system description generator for generating the current loudspeaker-enclosure-microphone system description based the plurality of wave-domain loudspeaker audio signals ( x̃ 0 ( n),... x̃ l ( n),..., x̃ N L -1 ( n)), and based on the plurality of wave-domain microphone audio signals ( d̃ 0 ( n),... d̃ m ( n),..., d̃ N M -1 ( n)), wherein the system description generator is configured to generate the loudspeaker-enclosure-microphone system description based on a plurality of coupling values, wherein each of the plurality of coupling values is assigned to one of a plurality of wave-domain pairs, each of the plurality of wave-domain pairs being a pair of one of the plurality of loudspeaker-signal-transformation values ( l; l') and one of the plurality of microphone-signal-transformation values ( m; m'), wherein the system description generator is configured to determine each coupling value assigned to a wave-domain pair of the plurality of wave-domain pairs by determining for said wave-domain pair at least one relation indicator indicating a relation between said one of the loudspeaker-signal-transformation values of said wave-domain pair and said one of the microphone-signal-transformation values of said wave-domain pair to generate the loudspeaker-enclosure-microphone system description.