Abstract: A known technique to improve bass reproduction in loudspeakers is by boosting amplitude at low frequencies, but this can lead to an overload at high signal level. This can be prevented if the level is detected in order to decrease the amplitude boost. To detect the level in the relevant frequency region, a band or high pass filter before the detector is normally used, but this creates a delay in regulation, so that a high signal peak can introduce audible distortion. The described arrangement prevents this, as the signal is led through a variable band pass filter (10) and directly to the detector (8), which therefore receives the full signal. The arrangement operates such that the lower cut-off frequency of the band pass filter changes so that the lowest frequency range gets the highest attenuation.