David Satz
Member
- Joined
- Sep 25, 2004
- Messages
- 9
Keith, regarding the sound of the U 87's low end: I can understand that the low-frequency response in the omni setting might be disappointing. But that's not only (or even mainly) due to the rolloff filter. The bottom end of an "omni" pattern that's synthesized by summing two cardioids never works, sounds or feels the same as the bottom end of a pressure transducer. There's a rolloff at whatever point (commonly 40 Hz or higher), there's great sensitivity to wind or breath noise and mechanical shock or handling noise, and there's even a little proximity effect. If you've been spoiled by "real" omnis (single-diaphragm pressure transducers), which don't tend to have those problems, you will be almost certainly be disappointed.
The low-frequency response of the cardioid setting in this type of microphone is part of what makes people like large-diaphragm condensers. However, I think many people have a big misconception about large diaphragms and low frequency response. It isn't so much the "largeness" of the diaphragm that gives these microphones this type of characteristic, but (if I can call it this) the "dualness." This is because typical dual-diaphragm condenser microphones in their cardioid setting (which is all that 90% of people ever use, unfortunately), actually has more of a "wide cardioid" characteristic at low frequencies--it picks up much more room sound. You can see this quite clearly if you look at the polar response of a Neumann U 47 or its modern counterpart, the M 147 Tube microphone; it is a wide cardioid on the bottom, a cardioid at mid frequencies only, and a supercardioid on top. Neumann even used to designate the U 47fet as a supercardioid at one point in the 1970s.
A single-diaphragm cardioid that is well made will not have this characteristic--it can maintain its cardioid pattern down to very low frequencies, even though its amplitude response is already rolling off. This means that its diffuse field response at low frequencies will generally parallel its on-axis (free-field) response much more closely than is the case with something like a U 47 or a U 67/87. Call that "warmth" if you want, but it has little to do with diaphragm size and much more to do with an off-axis response curve that's tilted way upward at the bottom:
(That's a U 67 in the cardioid setting--note the shape of its 180-degree response.)
Finally, figure-8 microphones have an inherent problem with low frequencies, because the force of the pressure gradient is proportional to the path length around the diaphragm as a fraction of the sound wavelengths. At lower frequencies this fraction diminishes proportionately, so you get a 6 dB/octave natural rolloff. At least it's easy to compensate for that electronically if you want to; Sennheiser builds compensation into their MKH 30 amplifier, but that can obviously be done only in a "unitary" microphone, not in modular microphones with interchangeable capsules. The thing is, even if you flatten out the response of a figure-8, its low end will never feel like that of what I called a "real omni" (a pressure transducer) even if the on-axis amplitude response is 100% identical. This is because we get a lot of cues about the space a recording was made in from low-frequency standing waves, but those are directional phenomena--so they are all picked up equally by pressure transducers, while figure-8 microphones (pure pressure gradient transducers) filter about 2/3 of them out, simply by virtue of their directional effect.
Does that make sense?
--best regards[/img]
The low-frequency response of the cardioid setting in this type of microphone is part of what makes people like large-diaphragm condensers. However, I think many people have a big misconception about large diaphragms and low frequency response. It isn't so much the "largeness" of the diaphragm that gives these microphones this type of characteristic, but (if I can call it this) the "dualness." This is because typical dual-diaphragm condenser microphones in their cardioid setting (which is all that 90% of people ever use, unfortunately), actually has more of a "wide cardioid" characteristic at low frequencies--it picks up much more room sound. You can see this quite clearly if you look at the polar response of a Neumann U 47 or its modern counterpart, the M 147 Tube microphone; it is a wide cardioid on the bottom, a cardioid at mid frequencies only, and a supercardioid on top. Neumann even used to designate the U 47fet as a supercardioid at one point in the 1970s.
A single-diaphragm cardioid that is well made will not have this characteristic--it can maintain its cardioid pattern down to very low frequencies, even though its amplitude response is already rolling off. This means that its diffuse field response at low frequencies will generally parallel its on-axis (free-field) response much more closely than is the case with something like a U 47 or a U 67/87. Call that "warmth" if you want, but it has little to do with diaphragm size and much more to do with an off-axis response curve that's tilted way upward at the bottom:
(That's a U 67 in the cardioid setting--note the shape of its 180-degree response.)
Finally, figure-8 microphones have an inherent problem with low frequencies, because the force of the pressure gradient is proportional to the path length around the diaphragm as a fraction of the sound wavelengths. At lower frequencies this fraction diminishes proportionately, so you get a 6 dB/octave natural rolloff. At least it's easy to compensate for that electronically if you want to; Sennheiser builds compensation into their MKH 30 amplifier, but that can obviously be done only in a "unitary" microphone, not in modular microphones with interchangeable capsules. The thing is, even if you flatten out the response of a figure-8, its low end will never feel like that of what I called a "real omni" (a pressure transducer) even if the on-axis amplitude response is 100% identical. This is because we get a lot of cues about the space a recording was made in from low-frequency standing waves, but those are directional phenomena--so they are all picked up equally by pressure transducers, while figure-8 microphones (pure pressure gradient transducers) filter about 2/3 of them out, simply by virtue of their directional effect.
Does that make sense?
--best regards[/img]
