You may be surprised at the response curves given when a filter is in the presence of reactive loads. A purely resistive load will provide damping for the filter to provide the smooth rolloff you expect. But a complex load having both resistive and reactive components will modify the filter pretty substantially. And the loudspeaker itself is a complex load, which the compensation circuit modifies. The bottom line is that the loudspeaker is an integral part of the filter circuit, and all components are inter-related. So you'll need to analyze the circuit in more detail to know its response.