Impedance must be examined on how it varies with frequency

How does the impedance of a particular mic varies with frequency? It should not be for example 200 ohms at all frequencies. Variations are expected at spectrum extremes but even on mid range too, who knows?


A very nice book on understanding impedance and how it can be easily measured in the lab (output or input impedance) from first principles is Electronics, a Systems Approach - Neil Storey.


How does the impedance of a preamplifier with a particular input transformer varies with frequency?


Can these compliment each other so that flat frequency response from singer's vocal chords to listener's brain is achieved?


For example:


The transferred loading of a signal transformer at high frequencies. A possible higher HF input impedance increasing the output of the mic at HF. Can leakage inductance in the transformer transfer a less load to the mic? So that at the same time the transformer response drops, the (voice coil) mic output increases because of less internal mic voltage drop, i.e, drop across its internal impedance, Thevenin's theorem.


A bass guitar pickup rises in HF the higher the load or amp input impedance. Here we have a frequency dependence or high cut filter made by the series inductance of the pickup and shunt input impedance of the preamp. Same as MM or NC record player cartridges that need to be terninated by specific load and specific capacitance.Capacitance plays an important role, parasitic or stray capacitance, cable capacitance too. When being a kid a record player was connected to a Sony FH-7 compo by increasing the cable length a few meters and how horrible bass heavy the sound became or high cut. MM cartridges are relative high Z voltage generators. There is a resonance ocurring by the coil inductance and the shunt terminating capacitance. Another day we connected an electric bass to the MM input and the woofers almost exploded, we did not know about the RIAA preemphasis deemphasis curve on records.


Another example is an amplifier of relative high output impedance sending a higher music voltage to a full range speaker at HF. This is because the impedance of the speaker being a coil rises with frequency ie loads less the amplifier. So there is less voltage drop at the internal amplifier or output resistance.


Ribbon or moving coil directional (not omni) microphones may give a reduced response at low frequencies as their output impedance increases at LF so there is more voltage drop.[Microphones - Burroughs]


Rising HF when a tape recording head is coupled to an anode. This helps achieve the recording characteristic. Again this happens as coil impedance increases by increasing frequency so there is less voltage drop at the tube internal output impedance, anode resistance or ra, bot to be confused with Ra wgich is the load we connect. Thevenin's theorem. [Applied Electronics - T.S. Gray - MIT]


High pass filtering when an inductor is connected in parallel with mic's output. Example inside an Electro=Voice RE-15,  RCA 77DX, switchable to cut bass for voice, singing use close use or music, same as Pleiades external inline filters etc


It is important to consider the system as a whole from singer's brain to listener's brain. [Sound picture recording and reproducing characteristics - Loye, Morgan, Journal of the Motion Picture Sound Engineers]