I am assuming that the reproduction potential of high-quality loudspeakers cannot be fully captured by measuring microphones (i used a UMIK-1 and the original supplied measuring microphone) ....For me this is a indication that the measuring method is probably the bottleneck here. It could be the same with the capacitor measurements.
A good measurement microphone will outperform the human ear in frequency resolution (depends on sampling rate), frequency range (10hz - >20khz) and dynamic range (>140dBspl <3%THD).
Condenser microphones are also used for studio recordings or live recordings. This means that if these microphones cannot fully pick up certain musical details, then these details will also not be present on the recording and especially not when the recordings are played back through "high-quality loudspeakers".