<The impulse response is the output that the mic would give if the stimulus it was given was an extremely brief pulse, in digital terms it would be one sample wide and no more for a given sample rate. The signal that the mic puts out in response to that impulse is, oddly enough, called its impulse response.
Contained in that is all of the information relative to the frequency response of the microphone when stimulated by a source at the position of the impulse generator. The most common would be on axis but with a directional mic, two on axis measurements at different distances will disclose its proximity effect and one should take measurements at a few other angles to do other kinds of magic with them.
These things aren't any good to look at, only a really trained eye will be able to tell much at all and that's not much but if you do a Fourier transform of that impulse response, you get the magnitude and phase of its frequency response across the spectrum, part of which you are used to seeing approximations to on data sheets.
In the most general and unqualified terms, if you know the impulse respones of two mics you can, with DSP techniques, make either sound like the other. The two processed together in a certain way will yield another impulse response that can be used via convolution to transform one to the other.
You don't actually measure these things with impulses, but rather with sinusoidal sweeps (or known noise patterns) and then apply a DSP process to the recording of that sweep that converts it into the impulse response.
Elaborate enough?
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Beautifull!!! Thanks Bob.
<you know you can hear odd-harmonic distortion brought upon by fast, cheap and bad designs.>
Sweetnubs,
I have been in music since 9 months before I was born and in audio for only about 25 years. I have designed and built all kind of equipment--speakers, amplifiers (mostly tube), tape recorders, line, phono and mic pres, turntables, DACs, mics of almost all kinds and configurations...
Some say that I have pretty good ears. But you know, to be honest, I never can say where are harmonic distortions, where are IM ones, where are odd, and where are even ('more pleasant') ones. But ones again, I am still new to it...
To me, to talk about you hear odd-harmonic distortions in such a low signal level device as a mic, sounds little bit odd, especially considering the fact that most of these mics are actually clones of very good designs. Most likely you hear bad quality parts. Right now I am working on MXL603 modification and can tell that mere change of parts for better quality ones makes significant difference. Has the amount of odd-harmonics changed?--no way. Has sound changed?--I will post clips later and you tell me.
Oh yeah, one more thing. I always talk about things I have experienced myself, or know about for sure. If not, I prefer to shut up and listen what more knowledgable people have to say.
Am I sceptical about what Bob talks about mic simulation? May be.... But I will refrain from any judgement until I try and see it myself.... 'cauze it seems that Bob knows what he is talking 'bout.