I hear this over and over again, and - although I want to believe it - I'm having some doubts. The coupling cap alone is so microphonic, that it acts as a microphone (tap that thing and you know what I mean). So it could very well be the cap you install as capsule replacement and/or the coupling cap.Not a stupid question at all. I do it by performing various measurements. Not quite a walk in the park. If you are going after a clone, it's not the point to get rid of it, but match it instead. This exact point is driving me nuts currently, as im trying to nail a c800 clone, but i'm nowhere near done.
There is a body resonance, there is resonance of the cavity of the body (helmholz resonance), there's resonances and reflections around the capsule, angle of the capsule compared to the perpendicular bar of the grille, upper and lower in case of u47/c800 and such.
Elam is for example easy, the point is to kill all the resonances. I even have a mic which doesn't need any grille/shielding. As complicated as it sounds it's way easier to do.
U87s goal is also to have least resonances and reflections around the capsule. Sleve of the body doesn't resonate at all.
These effects show up in frequency response graphs, and are not subtle, several db of peaks and notches all over the place.
In case of u47 which has fairly microphonic tube (contrary to what many believe), you can replace the capsule with a 50pf capacitor, and listen to just the mechanical ringing of the components (microphonics). You would be surprised how much of a drum kit sound (high spl) the mic would pick up
- Not talking about the body resonances, those are obvious, but the VF14M tube being "ridiculously microphonic"...