Cybergaloot, what you read is perfectly true AND it can be quite audible in everyday recording practice; it's not just an "academic" point.
You can find this out for yourself by making some test recordings--set up your mikes on a stand or at some distance above a tabletop, then speak into them and move your hands slowly closer and closer to the mikes. You can get some weird sounds due to partial cancellation at various frequencies (phase conflict due to reflections).
Last night I was watching the wonderful TV series "Slings and Arrows," and at some point during some dialog that was filmed outdoors, I realized that I was hearing the reflections from what must have been the relatively small booth in which the dialog had been re-recorded in post production. Perhaps you've had similar experiences of being able to tell the size of the recording venue from the sound on the recording (particularly noticeable when the sound source moves). What we're talking about here is the same effect on a slightly different scale.
Primarily this affects the high and mid-high frequencies, since low frequencies have long wavelengths and can "flow around" most obstacles that aren't the large-scale, rigid structural features of a room. But the wavelength of 1 kHz is only about 13 inches, and for any given wavelength, anything larger than about half of that size can deflect a significant part of the wave, causing reflection or diffraction.
That's why small-diaphragm microphones (and small microphones generally) are preferred for the type of recording that tries to recreate an accurate picture of the original sound. A large microphone "gets in its own way" at high frequencies, and the point in the spectrum at which that starts to be a problem is lower, the larger the microphone is. For most conventional large-diaphragm microphones the problem exists in the 2 - 4 kHz range (the most sensitive range of human hearing!) and above; smaller microphones can "postpone" these problems for another octave or two. This affects not only the frequency response and polar (directional) response, but also the impulse response in a major way.
Solid objects placed near microphones can benefit a recording, too, as in the case of PZMs, sphere stereo recording or the Jecklin plate approach. But to know in advance what type of setup is likely to work takes a knowledge of physics and psychoacoustics. Otherwise you can count on needing an enormous amount of experimentation, with most of the results being less than optimal.
--best regards
Topic: Could "stacking" miniature mics cause any problems? (Read 2037 times)