Change of impedance with respect to frequency of reactive elements can aid flat frequency response to listener's brain

(Inductors (coils for example),  capacitors are reactive elements.


For example amplifiers of not very low output impedance driving a fullrange moving coil speaker. See previous post.


Other example:
A coil in series with a resistor (Pleiades R,L gentle slope pass filter) connected across the voice coil of a microphone in order to reduce bass, mid heaviness to listener's brain or achieving flat frequency reponse from producer's brain to listener's brain.


See also:


Sound picture recording and reproducing characterizes - D. P. Lowe, K. F. Morgan - Journal of Society of Motion Picture Engineers