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Re: Good electret capsules?

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  • Matt
    Hi Sergei, I think you re misunderstanding my goal with this microphone. :) I do not want to make an omnidirectional spherical array mic. I m making a
    Message 1 of 7 , Nov 26, 2012
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      Hi Sergei,

      I think you're misunderstanding my goal with this microphone. :) I do not want to make an omnidirectional spherical array mic. I'm making a directional microphone that is shielded from both handling noise and wind (the sphere is, you could say, the case surrounding the two suspended directional mics inside).

      Kind of like in this video:

      http://www.youtube.com/watch?v=XoW5JZexfNE

      but instead of one cardioid, there would be two in an xy pattern, and the cage would be more spherical in shape.



      That's interesting stuff about mic matching! Thanks very much for taking the time to explain it. Do you think that I should try some generic cardioids, then, and try to match them? They seem cheap enough, but it wouldn't be worth it if the sound is going to be trashy. What are your thoughts on generic capsules? Can they sound okay in general? I know this Dell one sounds nice, but I feel it's the exception.

      Or should I go for the branded Panasonic 55a, which is more expensive but perhaps a bit better sounding? I don't think it's going to be worth it for me to get some other capsules from overseas; it would be too expensive for this project I think.

      I really want to have a look into 'summing up'. Just to be clear, all I have to do is...

      1) buy several capsules and find matching ones, both for sensitivity and frequency characteristics
      2) sum them up by connecting them in parallel

      Is this correct?


      Thanks a lot,
      Matt

      --- In micbuilders@yahoogroups.com, Sergei Steshenko <sergstesh@...> wrote:
      >
      > Regarding the microphone sphere. Either don't do it at all, or do it properly, with DSP. Try
      >
      > https://duckduckgo.com/?q=microphone+array+sphere
      >
      > and read, for example, http://www.umiacs.umd.edu/~ramani/cmsc828d_audio/spherical_arrays.pdf
      >
      >
      > Regarding omni <-> directional. Conceptually directional capsule is at least a couple of omnies separated in space and differently filtered, then summed up. From here we can go back to the above spherical array - there is space separation and filtering is done in DSP SW.
      >
      >
      > Regarding matched capsules. Capsules even of the same type are not identical. Even from the same batch. Even for the simplest stereo recording (two omnies or two cardioids) one needs matched characteristics - otherwise stereo image will be skewed and/or localization will be affected.
      >
      > For example, if HF response differs, localization of a musical tool capable of producing both highs and lows will depend on which spectrum it produces, and this depends, for example, on which part of the musical composition it plays.
      >
      > So, if you buy stereo microphone pair, good manufacturers promise certain degree of matching. And the better is the matching, the more expensive the microphones are. I think it's because more human labor (to measure capsules and to select good matches) is involved, but I might be wrong. Of course, capsules with better repeatability in manufacturing will cost more, so it's either expensive manufacturing or expensive selection.
      >
      > Regarding noise and summing up individual capsules. There is unavoidable _acoustic_ noise due to Brownian movement of air molecules.
      >
      > The way to do decrease this noise is through increasing diaphragm area. The noise is reduced because better averaging of Brownian movement is achieved.
      >
      > If summing up is done properly (first sensitivities are equalized, then the signals are summed up), using N smaller capsules is almost as good using a big capsule with area equal N areas of the small capsule.
      >
      > ...
      >
      > Even doing spherical arrays properly requires well matched capsules with known characteristics.
      >
      >
      >
      > Regards,
      >   Sergei.
      >
      >
      > >________________________________
      > > From: Matt <theguymjp@...>
      > >To: micbuilders@yahoogroups.com
      > >Sent: Monday, November 26, 2012 1:40 AM
      > >Subject: [micbuilders] Re: Good electret capsules?
      > >
      > >
      > > 
      > >Hi Sergei,
      > >
      > >I knew that it was likely that the Dell mic was generic, but there's no way to tell of consistency with generics hence my asking for and good branded recommendations.
      > >
      > >I need a directional mic, and omni won't do (as far as I know), especially because of the distance required to get good stereo with them. I'm building a 'microphone sphere', you see. The capsules will be suspended with silicone within a spherical mesh which has fluffy material all around it to prevent both wind and handling nose. It's going to be recording specific sound sources, rather than a general ambience, which is why I would have thought directional mics would be best so that they won't pick up sounds from behind the 'focus'. I should have explained all this in the first email. Sorry about that
      > >
      > >What do you mean by "matched capsules"? Is there sometimes a difference in volume between them?
      > >
      > >Also, that s/n improvement sounds very interesting! What do you mean by "summing up"? Would there be some electronics involved in that, or can it be done by simply connecting the + and - connections of a few capsules together? Or relay?
      > >
      > >Thanks very much for your assistance!
      > >
      > >Regards,
      > >Matt
      > >
      > >--- In micbuilders@yahoogroups.com, Sergei Steshenko <sergstesh@> wrote:
      > >>
      > >> Do you realize that the capsule you've ripped from the Dell laptop and which you apparently more rather than less is a generic capsule ? I.e. your Email contains an internal contradiction.
      > >>
      > >> For stereo recording you do not necessarily need directional microphones. A couple of omnies spaced 1.5 .. 2m apart is a known and simple way to record stereo, and IIRC this method is considered to produce good stereo recordings.
      > >>
      > >> I would buy a number of cheap capsules and try to find matched ones. Also, SNR can be improved by summing up signals from a number of capsules. I.e. you can create effectively an LDC by grouping SDCs.
      > >>
      > >> Regards,
      > >>   Sergei.
      > >>
      > >>
      > >> >________________________________
      > >> > From: Matt <theguymjp@>
      > >> >To: micbuilders@yahoogroups.com
      > >> >Sent: Sunday, November 25, 2012 1:13 PM
      > >> >Subject: [micbuilders] Good electret capsules?
      > >> >
      > >> >
      > >> > 
      > >> >Hi all! I'm building a stereo microphone, and I need two electrets for it.
      > >> >
      > >> >My primary concern is 'quality'. I'm building the mic for outdoor use, so ideally I want the sound to be rich and warm. It needs to be directional too, and a good signal to noise ratio would make it perfect.
      > >> >
      > >> >The problem is, I can't find anywhere to buy any capsules that aren't generic here in the UK. :( The only ones I can find are the Panasonic 55a for £3.50 each on ebay, and I have no idea if they're any good, so some advice would be greatly appreciated.
      > >> >
      > >> >I ripped a smaller than usual capsule out of an old Dell laptop a while ago, and its sound is absolutely amazing, especially for vocals. It sounds like a REALLY expensive non-electret. The problem is that it's omnidirectional, and it's a bit noisy. Fine for voices though, and the syllabus sound wonderful (which is often a problem for electrets I've found). Sounds noticeably better than my Zoom H2. I'd love to find a cardioid mic that sounds similar for this stereo project.
      > >> >
      > >> >Are there any other capsules that are available in the UK that are good? Thanks for any help! :)
      > >> >
      > >> >
      > >> >
      > >>
      > >
      > >
      > >
      > >
      > >
      >
    • Jerry Lee Marcel
      2) sum them up by connecting them in parallel Considering the application, I would really recommend the use of 3-wire capsules, and sum their outputs via
      Message 2 of 7 , Nov 26, 2012
      • 0 Attachment
        "2) sum them up by connecting them in parallel"
        Considering the application, I would really recommend the use of 3-wire
        capsules, and sum their outputs via isolation resistors (typically
        1kohm). 2-wire capsules, even of similar performance, have too much
        dispersion in their electrical characteristics; connecting them directly
        in parallels may see some being starved compared to others. You may use
        load-sharing resistors, but that would impair sensitivity and noise
        performance.


        Le 26/11/2012 10:47, Matt a écrit :
        >
        > Hi Sergei,
        >
        > I think you're misunderstanding my goal with this microphone. :) I do
        > not want to make an omnidirectional spherical array mic. I'm making a
        > directional microphone that is shielded from both handling noise and
        > wind (the sphere is, you could say, the case surrounding the two
        > suspended directional mics inside).
        >
        > Kind of like in this video:
        >
        > http://www.youtube.com/watch?v=XoW5JZexfNE
        >
        > but instead of one cardioid, there would be two in an xy pattern, and
        > the cage would be more spherical in shape.
        >
        > That's interesting stuff about mic matching! Thanks very much for
        > taking the time to explain it. Do you think that I should try some
        > generic cardioids, then, and try to match them? They seem cheap
        > enough, but it wouldn't be worth it if the sound is going to be
        > trashy. What are your thoughts on generic capsules? Can they sound
        > okay in general? I know this Dell one sounds nice, but I feel it's the
        > exception.
        >
        > Or should I go for the branded Panasonic 55a, which is more expensive
        > but perhaps a bit better sounding? I don't think it's going to be
        > worth it for me to get some other capsules from overseas; it would be
        > too expensive for this project I think.
        >
        > I really want to have a look into 'summing up'. Just to be clear, all
        > I have to do is...
        >
        > 1) buy several capsules and find matching ones, both for sensitivity
        > and frequency characteristics
        > 2) sum them up by connecting them in parallel
        >
        > Is this correct?
        >
        > Thanks a lot,
        > Matt
        >
        > --- In micbuilders@yahoogroups.com
        > <mailto:micbuilders%40yahoogroups.com>, Sergei Steshenko
        > <sergstesh@...> wrote:
        > >
        > > Regarding the microphone sphere. Either don't do it at all, or do it
        > properly, with DSP. Try
        > >
        > > https://duckduckgo.com/?q=microphone+array+sphere
        > >
        > > and read, for example,
        > http://www.umiacs.umd.edu/~ramani/cmsc828d_audio/spherical_arrays.pdf
        > <http://www.umiacs.umd.edu/%7Eramani/cmsc828d_audio/spherical_arrays.pdf>
        > >
        > >
        > > Regarding omni <-> directional. Conceptually directional capsule is
        > at least a couple of omnies separated in space and differently
        > filtered, then summed up. From here we can go back to the above
        > spherical array - there is space separation and filtering is done in
        > DSP SW.
        > >
        > >
        > > Regarding matched capsules. Capsules even of the same type are not
        > identical. Even from the same batch. Even for the simplest stereo
        > recording (two omnies or two cardioids) one needs matched
        > characteristics - otherwise stereo image will be skewed and/or
        > localization will be affected.
        > >
        > > For example, if HF response differs, localization of a musical tool
        > capable of producing both highs and lows will depend on which spectrum
        > it produces, and this depends, for example, on which part of the
        > musical composition it plays.
        > >
        > > So, if you buy stereo microphone pair, good manufacturers promise
        > certain degree of matching. And the better is the matching, the more
        > expensive the microphones are. I think it's because more human labor
        > (to measure capsules and to select good matches) is involved, but I
        > might be wrong. Of course, capsules with better repeatability in
        > manufacturing will cost more, so it's either expensive manufacturing
        > or expensive selection.
        > >
        > > Regarding noise and summing up individual capsules. There is
        > unavoidable _acoustic_ noise due to Brownian movement of air molecules.
        > >
        > > The way to do decrease this noise is through increasing diaphragm
        > area. The noise is reduced because better averaging of Brownian
        > movement is achieved.
        > >
        > > If summing up is done properly (first sensitivities are equalized,
        > then the signals are summed up), using N smaller capsules is almost as
        > good using a big capsule with area equal N areas of the small capsule.
        > >
        > > ...
        > >
        > > Even doing spherical arrays properly requires well matched capsules
        > with known characteristics.
        > >
        > >
        > >
        > > Regards,
        > > Â Sergei.
        > >
        > >
        > > >________________________________
        > > > From: Matt <theguymjp@...>
        > > >To: micbuilders@yahoogroups.com <mailto:micbuilders%40yahoogroups.com>
        > > >Sent: Monday, November 26, 2012 1:40 AM
        > > >Subject: [micbuilders] Re: Good electret capsules?
        > > >
        > > >
        > > >Â
        > > >Hi Sergei,
        > > >
        > > >I knew that it was likely that the Dell mic was generic, but
        > there's no way to tell of consistency with generics hence my asking
        > for and good branded recommendations.
        > > >
        > > >I need a directional mic, and omni won't do (as far as I know),
        > especially because of the distance required to get good stereo with
        > them. I'm building a 'microphone sphere', you see. The capsules will
        > be suspended with silicone within a spherical mesh which has fluffy
        > material all around it to prevent both wind and handling nose. It's
        > going to be recording specific sound sources, rather than a general
        > ambience, which is why I would have thought directional mics would be
        > best so that they won't pick up sounds from behind the 'focus'. I
        > should have explained all this in the first email. Sorry about that
        > > >
        > > >What do you mean by "matched capsules"? Is there sometimes a
        > difference in volume between them?
        > > >
        > > >Also, that s/n improvement sounds very interesting! What do you
        > mean by "summing up"? Would there be some electronics involved in
        > that, or can it be done by simply connecting the + and - connections
        > of a few capsules together? Or relay?
        > > >
        > > >Thanks very much for your assistance!
        > > >
        > > >Regards,
        > > >Matt
        > > >
        > > >--- In micbuilders@yahoogroups.com
        > <mailto:micbuilders%40yahoogroups.com>, Sergei Steshenko <sergstesh@>
        > wrote:
        > > >>
        > > >> Do you realize that the capsule you've ripped from the Dell
        > laptop and which you apparently more rather than less is a generic
        > capsule ? I.e. your Email contains an internal contradiction.
        > > >>
        > > >> For stereo recording you do not necessarily need directional
        > microphones. A couple of omnies spaced 1.5 .. 2m apart is a known and
        > simple way to record stereo, and IIRC this method is considered to
        > produce good stereo recordings.
        > > >>
        > > >> I would buy a number of cheap capsules and try to find matched
        > ones. Also, SNR can be improved by summing up signals from a number of
        > capsules. I.e. you can create effectively an LDC by grouping SDCs.
        > > >>
        > > >> Regards,
        > > >> Â Sergei.
        > > >>
        > > >>
        > > >> >________________________________
        > > >> > From: Matt <theguymjp@>
        > > >> >To: micbuilders@yahoogroups.com
        > <mailto:micbuilders%40yahoogroups.com>
        > > >> >Sent: Sunday, November 25, 2012 1:13 PM
        > > >> >Subject: [micbuilders] Good electret capsules?
        > > >> >
        > > >> >
        > > >> >Â
        > > >> >Hi all! I'm building a stereo microphone, and I need two
        > electrets for it.
        > > >> >
        > > >> >My primary concern is 'quality'. I'm building the mic for
        > outdoor use, so ideally I want the sound to be rich and warm. It needs
        > to be directional too, and a good signal to noise ratio would make it
        > perfect.
        > > >> >
        > > >> >The problem is, I can't find anywhere to buy any capsules that
        > aren't generic here in the UK. :( The only ones I can find are the
        > Panasonic 55a for £3.50 each on ebay, and I have no idea if they're
        > any good, so some advice would be greatly appreciated.
        > > >> >
        > > >> >I ripped a smaller than usual capsule out of an old Dell laptop
        > a while ago, and its sound is absolutely amazing, especially for
        > vocals. It sounds like a REALLY expensive non-electret. The problem is
        > that it's omnidirectional, and it's a bit noisy. Fine for voices
        > though, and the syllabus sound wonderful (which is often a problem for
        > electrets I've found). Sounds noticeably better than my Zoom H2. I'd
        > love to find a cardioid mic that sounds similar for this stereo project.
        > > >> >
        > > >> >Are there any other capsules that are available in the UK that
        > are good? Thanks for any help! :)
        > > >> >
        > > >> >
        > > >> >
        > > >>
        > > >
        > > >
        > > >
        > > >
        > > >
        > >
        >
        >



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