An unknown content audio signal that is input to an audio power amplifier and speaker that have a known gain and speaker sensitivity, is buffered. A portion of the buffered signal is provided to an automatic content recognition (ACR) system, and then a content identifier, of the unknown content signal, as provided by the ACR system is received. Previously determined metadata is also received, for a reference audio content signal that has been assigned to the content identifier. The metadata includes a previously determined reference measure of an audio signal characteristic for the reference content. An input measure of the audio signal characteristic is computed, for the unknown content, and compared with the reference measure. On that basis, and also based on the known gain and speaker sensitivity, at least one of a scalar gain and spectral shaping filtering that is being applied to the unknown content is adjusted. Other embodiments are also described and claimed.