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Topic: Large diaphragm mics

  1. #1

    Large diaphragm mics

    Can anyone send me to some sources about research on the size of mic diaphragms? What effect does the size of the diaphram have the on accuracy of the recorded sound?

    There are standard circumferences, but are these compromises? Would the ideal mic for a bass drum have the same circumfurence as the head of the bass drum?

  2. #2

    Re: Large diaphragm mics

    Wow, no response at all?

    I know it seems absurd, thinking in terms of huge diaphragms for a mic, but I\'m thinking in terms of sound theory. (Yes, the next questions I would ask are: has anyone made recordings using an enormous mic\\diaphragm, and why one of these couldn\'t be created fairly easily. Would one be that such a mic could be too sensitive, raising the noise floor to an incredible height?)

  3. #3

    Re: Large diaphragm mics

    as far as I know, and I\'m probably wrong, the size of the diaphragm isn\'t relative to the quality, or realism, of the signal gained, but the material of the diaphragm is.

    I can\'t really see how a huge diaphragm is going to achieve anything better than what a small diaphragm does. In fact, you\'re probably right. If there was a huge surface that acted as a siaphragm, it would probably pick up so much undesired noise that it would be useless.

    That\'s just me common sense laddy!!

  4. #4

    Re: Large diaphragm mics

    Regarding the size of mics, the biggest point is the relation between mic size and sound wavelength. When sound wavelength is smaller than mic\'s capsules, the response begin to change (a little boost).
    Other important factor is the more directivity in frequencies with wavelength smaller than mic\'s capsule.

    That is why measure mics, which should have omni response in all freq. have small capsules. People usualy don\'t use large capsule mics in orchestra because they tend to became more directional in high frequencies which result in an off-axis non-flat response.

    Regarding big capsules mics, i think yamaha was working on a special very large mic to bass drums (since they have large wavelengths). Try to see yamaha site...

    Regarding Signal to Noise Ratio, the bigger the better...

  5. #5
    Senior Member Bruce A. Richardson's Avatar
    Join Date
    Sep 1999
    Dallas, Texas

    Re: Large diaphragm mics

    Hi Jake,

    I think the reason people don\'t respond to some of these questions is that they\'re all really standard-issue engineering fare, and you can get this information literally everywhere. There are entire books written on this subject. You can search this stuff out all over the internet. On Shure\'s site alone, there are probably 25 online publications which go into great detail about microphone design, engineering methods, pros/cons, and assorted other tidbits.

    I can give you a little info, but hey, I charge money for this kind of writing/education/consulting, you know?? Nuno\'s information is all good. I can put some more perspective on it, but it just can\'t be covered in enough detail in a forum like this to have much result except adding to the confusion and begging more questions.

    The reasons people use large diaphragm mics are all about how one wants to design the overall soundscape of a given production. Technicalia aside, it\'s just how different mics sound on different things, and what someone\'s taste discerns as pleasing. Large diaphragm microphones\' characteristics produce tracks we perceive as \"intimate\" very well, because they accentuate those aural cues. They \"catch\" a lot of air. This is also their negative, that in a noisy or uncontrolled environment, they\'re going to pick up lots of stuff you may not want. It\'s all a matter of choice and taste and desired result. An engineer\'s primary toolkit is his selection and placement of microphones--they are the technical equivalent to an orchestrator\'s choice of which section will play what part. A person who has done enough vocal sessions will generally hear a person\'s voice and know pretty much which of his microphone selections he\'ll try first, and what he\'ll try second and third if the first doesn\'t give him what he\'s looking for. Conversely, he may use a different mic on the same singer, just to put the vocal in a different space.

    Same with instruments.

    Condensers are more sensitive than ribbons, which are more sensitive than dynamics, which are more sensitive than early, now mostly unused designs. The smaller the diaphragm, the higher the self-noise of the mic in general. The smaller the diaphragm, the more frequency/distance linearity (hence Nuno\'s example of test mics, for instance those by Earthworks, having teeny diaphragms). Conversely, tiny diaphragm mics tend to be very cold and truthful, not necessarily what someone might call \"musical.\" Rarely is absolute \"truth\" the best sound one can get. Some mics are nicer to certain sounds than others. The larger the diaphragm, the more pronounced color changes will be as caused by proximity, which is why engineers use them a lot, and move them around inches at a time until they get the specific tracking sound they\'re after.

    And all of this is why there are no easy pat answers when it comes to what mic and what distance a person chose for a sample library. By necessity, people have to make a choice and stick with it, otherwise the samples are quite literally all over the place. But where an engineer on a live session would have the overall production\'s context from which to derive the placement/microphone choices, someone sampling for sample libraries just has to decide on some method which he feels will either serve a specific use very well, or which will, in his knowledge, be generically useful and tweakable in post production.

    Regarding kick drum mics, these are generally large diaphragm, dynamic (rather than more sensitive condenser) mics. Why? You want the \"oomph\" that the large diaphragm gives (AKG\'s D112 is one example of these \"kick\" mics), but you don\'t want super high sensitivity, so that every creak, squeak, rattle, and other drum sound is in there muddying up the works. In other words, you could get the same punch out of a U87, but you\'d also be getting a lot of extraneous crap in the track you\'d just have to gate or expand out. Better to use a mic that doesn\'t get that stuff in the first place. People use RE20s on kicks, saxes, and bass cabinets for the same reason--they pick up the things we consider musical about those instruments, and tend to reject or just not hear the things that clutter up those sounds. It\'s a radio D.J. mic of choice as well, for the very same reason. It gives a nice masculine sound, with good intimacy and isolation from the room. Similarly, these reasons are why people use 57s on snares, even though a 57 looks terrible on paper compared to so-called \"better\" mics. First of all, a 57 just happens to sound fantastic on snares by serendipity, but logically, it works because you don\'t want a lot of sensitivity and leakage there--you want as much isolation as you can get, so that you have control in the mix over affecting the snare without affecting everything in the whole kit. You have the overheads, usually nice condensers there, to be sensitive and catch the overall sound of the kit in a stereo perspective. The spot mics are all about adding some presence and correctional/fx potential to the stereo image generated by the overheads. One of the big mistakes beginning engineers make is thinking that the primary sound of the kit comes from the spots. Just the opposite--in a good room, the kit\'s almost entirely represented by the overheads, with just enough spots in there to put the intimacy where you need it, and to do things like getting a good ballsy snare, kick, and floor tom. Or in the case of hi-hats, the spot is there just to allow some focus and sheen if it\'s needed. In the case of toms, the spots are generally there so you can compress the living crap out of them and use that result to dial in additional sustain and \"tone\" if it\'s needed.

    See what I mean about the subject of microphones? It would take me another 100 pages to discuss even the most rudimentary applications, and then, that would be short-changing any one of them.

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