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#1
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mic question (bass boost/phase)
hello everyone,
some mic designs like large-diaphragm cardioid condensers will have the bass response boosted if you put the mic very close to the sound source. is this because of phase issues? i learned that the presence peak that many mics have is due to phase stuff inside the capsule, so i was wondering if this is somehow related. |
#2
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wrote:
some mic designs like large-diaphragm cardioid condensers will have the bass response boosted if you put the mic very close to the sound source. is this because of phase issues? It's because of the cardioid pattern. I think how the proximity effect works is discussed in the FAQ. I know there was a long discussion of this here a couple years ago. EV used to also have a nice discussion of this on the glossy sheet for the RE-20. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#3
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In article , Scott Dorsey
wrote: wrote: some mic designs like large-diaphragm cardioid condensers will have the bass response boosted if you put the mic very close to the sound source. is this because of phase issues? It's because of the cardioid pattern. I think how the proximity effect works is discussed in the FAQ. I know there was a long discussion of this here a couple years ago. EV used to also have a nice discussion of this on the glossy sheet for the RE-20. --scott Here, read this: https://www.neumann.com/infopool/dow...i=docu0002.PDF ulysses |
#4
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wow, thanks for the link!
that's some thick, meaningful reading. i will read it bit by bit. |
#5
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Generic, the bass boost that you're talking about is called "proximity
effect." Unfortunately its cause is difficult to explain concisely. It involves [a] the gradual change in shape of the wavefronts as sound radiates outward from a point source (or something like one), and [b] the fact that any pressure gradient transducer is exposed to the sound field at more than one point. A sound that originates in front of the diaphragm will eventually reach the back of the capsule, too, but only after it has traveled a greater distance. When a sound source is very close to the diaphragm and in front of it, the inch or so of extra path length for the sound to reach the back of the diaphragm (or the rear diaphragm in a dual-diaphragm capsule) is proportionately quite significant. The sound waves are spreading out in all directions, and the wavefronts, which initially tend to be sharply curved near the sound's point of origin, tend to flatten out gradually as the sound travels. Try sketching a set of concentric circles plus a one-inch straight line that intersects each of them in turn, and you'll see what I mean--the farther the circles get from the point of origin, the more nearly the section of arc will approximate the one-inch straight line. Now if a wave is more nearly spherical when it strikes one side of the capsule but more nearly plane when it strikes the other side, there will be a greater resulting force than if the wavefront had the same shape on both sides. The output of a pressure-gradient transducer is proportional to the difference between the sound pressure at the front and back of the capsule. So ultimately it's that discrepancy in wavefront shape between the front and back of the capsule that causes the bass boost. As a corollary, note that a cardioid has no proximity effect 90 degrees off axis, and that a supercardioid or a figure-8 will have stronger proximity effect than the corresponding cardioid. --best regards |
#6
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David Satz wrote: Now if a wave is more nearly spherical when it strikes one side of the capsule but more nearly plane when it strikes the other side, there will be a greater resulting force than if the wavefront had the same shape on both sides. The output of a pressure-gradient transducer is proportional to the difference between the sound pressure at the front and back of the capsule. So ultimately it's that discrepancy in wavefront shape between the front and back of the capsule that causes the bass boost. I'd thought this too but came to wonder why the effect, as described, would be at all frequency dependant. Bob -- "Things should be described as simply as possible, but no simpler." A. Einstein |
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