Please: It's fundamentally impossible for any one type of omnidirectional microphone to be optimal in all recording situations.
Problem #1: If the microphone is to remain fully omnidirectional at the highest audible frequencies, it must have a very small capsule. Unfortunately, then it won't be quiet enough to meet the normal requirements of most modern recording (especially digital).
Problem #2: Conversely, a normal-sized (say 20 - 25 mm diameter) small-diaphragm condenser microphone with adequate signal-to-noise ratio cannot be fully omnidirectional at the highest audible frequencies; typically there will be a significant narrowing of its directional pattern above, say, 5 - 8 kHz. Thus the off-axis response is typically about 6 dB below the on-axis response at high frequencies.
Problem #3: The farther away you get from the sources of sound in a room, the more times (on average) the sound that reaches your microphones will have bounced off the floor, ceiling, walls, furniture, people, etc. first, and the more the high frequency content of that sound will have been absorbed in the process. For that reason among others, the diffuse sound in a room is usually quite a bit less bright-sounding than the direct sound in the same room. This only multiplies problem #2.
As a result, for acoustical measurement work two main, contrasting types of omnidirectional condenser microphone are typically produced: free-field equalized (i.e. for use where direct sound predominates--either in an anechoic environment, or outdoors, or very close to the sound sources) and diffuse-field equalized (i.e. for use in reverberant environments at a distance from the sound source where reflected sound energy predominates). The free-field type could have flat response on axis (and by implication a response rolloff off axis) while the diffuse-field type may have a significant on-axis elevation, but this won't sound harsh or unnatural when the microphone is actually used in a diffuse sound field, because the sound itself will be rolled off and because it will mostly arrive off-axis.
Please see the two attached frequency response graphs below, which are from Neumann, and note that the two microphones have nearly identical polar response. The KM 131 has free-field equalization and measures very flat on axis (conventional frequency response measurements are free-field measurements, or at least they're supposed to be), while the KM 130 has diffuse-field equalization and would measure close to flat if we were looking at its integrated response considering all possible angles of incidence--but since the published curve is a 0-degree free-field measurement instead, it shows a substantial high-frequency peak. The Schoeps counterparts would be the MK 2 and MK 3 capsules respectively, or the CCM 2 and CCM 3 microphones. DPA has counterparts, too, which I'm sure someone will eagerly post (I don't know their product line at all well).
The thing is, most of the time when you record music, you're somewhere between these two extreme conditions--so you want microphones whose frequency response is somewhere between free-field and diffuse-field equalization. Exactly where along that spectrum will depend on where you intend to place the microphones and what the acoustical environment will be like, as well as personal taste and preference. As a result, one type of omnidirectional microphone cannot possibly be optimal in all recording situations, so the notion of one absolute best omnidirectional microphone for music recording is fundamentally absurd--even more than is generally the case with microphone preferences. This isn't a matter of pluralism or tolerance or liberal philosophy or respect for others or "different strokes for different folks"; it's physics.
--best regards
Topic: Favorite Omnis (Read 12021 times)