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Re: [micbuilders] two dishes for stereo (was Parabolic Dish + Head Spaced Boundary

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  • Rob Danielson
    ... Hi Mike-- For your curiosity.,.. in 1973: http://www.wildlife-sound.org/journal/archive/stereo1.html Rob D. -- [Non-text portions of this message have been
    Message 1 of 28 , Mar 31 10:30 PM
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      At 8:40 PM -0500 3/31/08, Mike Feldman wrote:
      >On 31 Mar, 2008, at 8:05 PM, umashankar mantravadi wrote:
      >> if i can chime in, i do not think there is real stereo possible
      >> with a parabolic dish.
      >>
      >> if you want to think like this, the m part of the signal is a
      >> narrow spot a few hundred
      >>
      >> yards away, and the s is the area around you. the two cannot match.
      >>
      >
      >What if you were to use two parabolic dishes,
      >each with a single mic at the focus, and aim
      >them on either side of that spot a few hundred
      >yards away?
      >
      >-- Mike
      >
      >

      Hi Mike--
      For your curiosity.,.. in 1973:
      http://www.wildlife-sound.org/journal/archive/stereo1.html
      Rob D.
      --


      [Non-text portions of this message have been removed]
    • krokavadet
      ... match. ... Parabolic Dish and Primo EM-23 (or EM-21) capsules, that is what Klas Strandberg of Telinga Microphones are using too.
      Message 2 of 28 , Apr 1, 2008
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        --- In micbuilders@yahoogroups.com, Rob Danielson <type@...> wrote:
        >
        > At 8:40 PM -0500 3/31/08, Mike Feldman wrote:
        > >On 31 Mar, 2008, at 8:05 PM, umashankar mantravadi wrote:
        > >> if i can chime in, i do not think there is real stereo possible
        > >> with a parabolic dish.
        > >>
        > >> if you want to think like this, the m part of the signal is a
        > >> narrow spot a few hundred
        > >>
        > >> yards away, and the s is the area around you. the two cannot
        match.
        > >>
        > >
        > >What if you were to use two parabolic dishes,
        > >each with a single mic at the focus, and aim
        > >them on either side of that spot a few hundred
        > >yards away?
        > >
        > >-- Mike
        > >
        > >
        >
        > Hi Mike--
        > For your curiosity.,.. in 1973:
        > http://www.wildlife-sound.org/journal/archive/stereo1.html
        > Rob D.
        > --
        >
        >
        > [Non-text portions of this message have been removed]


        Parabolic Dish and Primo EM-23 (or EM-21) capsules, that is what
        Klas Strandberg of Telinga Microphones are using too.

        http://www.telinga.com/attach.htm

        http://www.telinga.com/stereo.htm

        Here are some pictures of the Telinga microphones:
        http://www.rogerbook.com/Utrustn.htm


        Roger
        >
      • rick chinn
        A chance bit of surfing tonight led to the discovery of James West and Gerhard Sessler (Bell Labs) as the inventors of the modern Electret Microphone in 1962.
        Message 3 of 28 , Apr 2, 2008
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          A chance bit of surfing tonight led to the discovery of James West
          and Gerhard Sessler (Bell Labs) as the inventors of the modern
          Electret Microphone in 1962.

          There is more information than is easily uploadable, so I will
          instead direct you to make your own search:

          go to:
          http://depatisnet.dpma.de/DepatisNet/depatisnet?window=1&space=unknown&content=index&action=index&session=c23b66f330d98e8eacf60a7748b2b77a8b95deee133e&stamp=105931

          or if your browser munges the long link:
          http://tinyurl.com/25bnly

          This is the German Patent Office's website, English user interface.

          In the upper left corner, click "SEARCH"

          Choose "Beginner" as the search mode.

          In the first field, "Publication Number" Enter US in the smaller of
          the two fields.

          In the field, "Applicant" enter "Bell"

          In the field, "Inventor" enter "James West"

          In the second (lower) options area, check those options that you want
          to see in the search results.

          In the "Results/page" dropdown menu, select 50.

          Now click the "Start Search" button.

          The Search results now appear.
          on the right side of the table, there is an Adobe PDF icon. Click
          that icon to see the first page of the patent.

          Once you've done that, there is a link at the upper right that lets
          you see the entire patent, text, illustrations, and all.

          Within the body of West's patents, there is some discussion of the
          process by which electrets are made. You'll also note that the
          initial patents were actually for earphones, but the patents also
          mention that by reciprocity, the same principles apply to microphones as well.

          His most recent patent was granted in 2005, without mention of Bell
          Labs, so perhaps he has retired. He is still around and doing things:
          http://www.eetimes.com/showArticle.jhtml?articleID=203100808


          Now, search for this patent: GB 1333847

          To do so, reset the patent search page, enter GB in the first field
          of the Publication Number, and enter 1333847 in the next field.

          Click the "start search" button. This brings up a british patent
          describing a method of making electrets.

          The short version of the search is that you need a high-temperature
          oven (130-150C) and a way to generate a high-voltage electrostatic field.

          --rick chinn

          here is the page that led to finding all of this:
          http://latimesblogs.latimes.com/kareem/2008/02/dr-james-west.html

          http://inventors.about.com/library/inventors/blwest.htm

          Another route to the German Patent Office's site is via the AES
          Historical Committee: http://www.aes.org/aeshc/ (see "Search: Patents
          of all countries"

          I prefer this site over the USPTO site because they make it much
          easier to download the text of entire patents. The Google patent site
          is also recommended, but it apparently does not extend its coverage
          worldwide. the UK patent, above, did not resolve when searched for.
        • umashankar mantravadi
          dear rick i remember reading somewhere that the browin tape sold as wondertape is attually en electret film. they apparently charge the film so it does not
          Message 4 of 28 , Apr 2, 2008
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            dear rick

            i remember reading somewhere that the browin tape sold as 'wondertape' is attually en electret film. they apparently charge the film so it does not stick to itself. maybe one should investigate various self adhesive tapes. if one is making a back electret. this tape will be glued to the backplate, so thickness may not matter that much. or does it? i have not thought through this.

            umashankar

            i have published my poems. read (or buy) at http://stores.lulu.com/umashankar


            To: micbuilders@yahoogroups.comFrom: rickc@...: Wed, 2 Apr 2008 02:33:12 -0700Subject: Re: [micbuilders] Electret Microphones




            A chance bit of surfing tonight led to the discovery of James West and Gerhard Sessler (Bell Labs) as the inventors of the modern Electret Microphone in 1962.There is more information than is easily uploadable, so I will instead direct you to make your own search:go to: http://depatisnet.dpma.de/DepatisNet/depatisnet?window=1&space=unknown&content=index&action=index&session=c23b66f330d98e8eacf60a7748b2b77a8b95deee133e&stamp=105931or if your browser munges the long link:http://tinyurl.com/25bnlyThis is the German Patent Office's website, English user interface.In the upper left corner, click "SEARCH"Choose "Beginner" as the search mode.In the first field, "Publication Number" Enter US in the smaller of the two fields.In the field, "Applicant" enter "Bell"In the field, "Inventor" enter "James West"In the second (lower) options area, check those options that you want to see in the search results.In the "Results/page" dropdown menu, select 50.Now click the "Start Search" button.The Search results now appear.on the right side of the table, there is an Adobe PDF icon. Click that icon to see the first page of the patent.Once you've done that, there is a link at the upper right that lets you see the entire patent, text, illustrations, and all.Within the body of West's patents, there is some discussion of the process by which electrets are made. You'll also note that the initial patents were actually for earphones, but the patents also mention that by reciprocity, the same principles apply to microphones as well.His most recent patent was granted in 2005, without mention of Bell Labs, so perhaps he has retired. He is still around and doing things:http://www.eetimes.com/showArticle.jhtml?articleID=203100808Now, search for this patent: GB 1333847To do so, reset the patent search page, enter GB in the first field of the Publication Number, and enter 1333847 in the next field.Click the "start search" button. This brings up a british patent describing a method of making electrets.The short version of the search is that you need a high-temperature oven (130-150C) and a way to generate a high-voltage electrostatic field.--rick chinnhere is the page that led to finding all of this:http://latimesblogs.latimes.com/kareem/2008/02/dr-james-west.htmlhttp://inventors.about.com/library/inventors/blwest.htmAnother route to the German Patent Office's site is via the AES Historical Committee: http://www.aes.org/aeshc/ (see "Search: Patents of all countries"I prefer this site over the USPTO site because they make it much easier to download the text of entire patents. The Google patent site is also recommended, but it apparently does not extend its coverage worldwide. the UK patent, above, did not resolve when searched for.






            _________________________________________________________________
            Fashion Channel : Want to know what�s the latest in the fashion world ? You have it all here on MSN Fashion.
            http://lifestyle.in.msn.com/

            [Non-text portions of this message have been removed]
          • rick chinn
            One of West s patents involves a method for measuring the charge retention of an electret film. --rick
            Message 5 of 28 , Apr 2, 2008
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              One of West's patents involves a method for measuring the charge
              retention of an electret film.

              --rick

              At 05:50 AM 4/2/2008, you wrote:
              >dear rick
              >
              >i remember reading somewhere that the browin tape sold as
              >'wondertape' is attually en electret film. they apparently charge
              >the film so it does not stick to itself. maybe one should
              >investigate various self adhesive tapes. if one is making a back
              >electret. this tape will be glued to the backplate, so thickness may
              >not matter that much. or does it? i have not thought through this.
              >
              >umashankar
              >
              >i have published my poems. read (or buy) at http://stores.lulu.com/umashankar
              >
              >
              >To: micbuilders@yahoogroups.comFrom: rickc@...: Wed, 2
              >Apr 2008 02:33:12 -0700Subject: Re: [micbuilders] Electret Microphones
              >
              >
              >
              >
              >A chance bit of surfing tonight led to the discovery of James West
              >and Gerhard Sessler (Bell Labs) as the inventors of the modern
              >Electret Microphone in 1962.There is more information than is easily
              >uploadable, so I will instead direct you to make your own search:go
              >to:
              >http://depatisnet.dpma.de/DepatisNet/depatisnet?window=1&space=unknown&content=index&action=index&session=c23b66f330d98e8eacf60a7748b2b77a8b95deee133e&stamp=105931or
              >if your browser munges the long link:http://tinyurl.com/25bnlyThis
              >is the German Patent Office's website, English user interface.In the
              >upper left corner, click "SEARCH"Choose "Beginner" as the search
              >mode.In the first field, "Publication Number" Enter US in the
              >smaller of the two fields.In the field, "Applicant" enter "Bell"In
              >the field, "Inventor" enter "James West"In the second (lower)
              >options area, check those options that you want to see in the search
              >results.In the "Results/page" dropdown menu, select 50.Now click the
              >"Start Search" button.The Search results now appear.on the right
              >side of the table, there is an Adobe PDF icon. Click that icon to
              >see the first page of the patent.Once you've done that, there is a
              >link at the upper right that lets you see the entire patent, text,
              >illustrations, and all.Within the body of West's patents, there is
              >some discussion of the process by which electrets are made. You'll
              >also note that the initial patents were actually for earphones, but
              >the patents also mention that by reciprocity, the same principles
              >apply to microphones as well.His most recent patent was granted in
              >2005, without mention of Bell Labs, so perhaps he has retired. He is
              >still around and doing
              >things:http://www.eetimes.com/showArticle.jhtml?articleID=203100808Now,
              >search for this patent: GB 1333847To do so, reset the patent search
              >page, enter GB in the first field of the Publication Number, and
              >enter 1333847 in the next field.Click the "start search" button.
              >This brings up a british patent describing a method of making
              >electrets.The short version of the search is that you need a
              >high-temperature oven (130-150C) and a way to generate a
              >high-voltage electrostatic field.--rick chinnhere is the page that
              >led to finding all of
              >this:http://latimesblogs.latimes.com/kareem/2008/02/dr-james-west.htmlhttp://inventors.about.com/library/inventors/blwest.htmAnother
              >route to the German Patent Office's site is via the AES Historical
              >Committee: http://www.aes.org/aeshc/ (see "Search: Patents of all
              >countries"I prefer this site over the USPTO site because they make
              >it much easier to download the text of entire patents. The Google
              >patent site is also recommended, but it apparently does not extend
              >its coverage worldwide. the UK patent, above, did not resolve when
              >searched for.
              >
              >
              >
              >
              >
              >
              >_________________________________________________________________
              >Fashion Channel : Want to know what's the latest in the fashion
              >world ? You have it all here on MSN Fashion.
              >http://lifestyle.in.msn.com/
              >
              >[Non-text portions of this message have been removed]
              >
              >
              >------------------------------------
              >
              >Yahoo! Groups Links
              >
              >
              >
            • Richard Lee
              ... What s not widely known is that ALL plastic film is electret to some extent. This is particularly so for good insulators like mylar. The manufacturing
              Message 6 of 28 , Apr 4, 2008
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                > One of West's patents involves a method for measuring the charge retention of an electret film.

                What's not widely known is that ALL plastic film is electret to some extent. This is particularly so for good insulators like mylar. The manufacturing and rolling generates kV of static electricity.

                This is a problem as mylar is the most common capacitor mike diaphragm and the electret charge is not stable. Metallisation can also introduce more charge.

                At Calrec, this was a serious problem for us when we had to buy new film.


                --
                No virus found in this outgoing message.
                Checked by AVG.
                Version: 7.5.519 / Virus Database: 269.22.6/1360 - Release Date: 4/04/08 18:02
              • tk7859
                Hello Scott and the Group Today I finished making the capsule mixing/power supply unit as per your schematic mentioned in the post (below). I used your
                Message 7 of 28 , Apr 14, 2008
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                  Hello Scott and the Group

                  Today I finished making the capsule mixing/power supply unit as per
                  your schematic mentioned in the post (below). I used your suggested
                  values of resistors and capacitors, but added a couple more, same
                  value, capacitors to keep the PIP voltage from the minidisc out of the
                  circuit.

                  I am delighted to report it works perfectly. In my preliminary tests
                  I could hear no noise when using the potentiometer to zoom from wide
                  stage boundary to focussed parabolic.

                  Today, for testing, I used the lash up as seen here

                  http://ad2004.hku.nl/naturesound/TomR/PRHSB2/P4140001.JPG

                  Photos of the actual unit are here

                  http://ad2004.hku.nl/naturesound/TomR/PRHSB2/P4140002.JPG

                  and here

                  http://ad2004.hku.nl/naturesound/TomR/PRHSB2/P4140004.JPG

                  During the next couple of days I will put the unit into a suitable
                  container and do some field tests. I will post the results on
                  "micbuilders".

                  The parabolic reflector used today was my new "lightweight" dish,
                  completed last Saturday. I will post on "naturerecordists" regarding
                  its development.

                  When I completed the prototype PDHSB I set myslf three targets
                  1) Make a lighter version
                  2) Try and eradicate the noise of the potentiometer, and
                  3) Find a replacement for the four, cheapo, Rapid capsule triplets
                  currently used for the boundary and focal point microphones.

                  The first two targets have almost been acheived. Got to start
                  thinking about those capsules :-)

                  Many thanks to you Scott and the rest of the Group for your help and
                  encouragement

                  Cheers

                  Tom Robinson

                  --- In micbuilders@yahoogroups.com, Scott Helmke <scott@...> wrote:
                  >
                  > Hi Tom,
                  >
                  > Neat looking mic design. I hadn't heard of that approach at all.
                  >
                  > It looks like the problem with potentiometer noise is that you're
                  > passing DC through the pots. Really no way to avoid noise in that
                  > situation. A slightly more complicated circuit would send the DC and
                  > the AC on separate paths. Looks like it would be easy enough to expand
                  > the power supply section to feed each set of capsules separately, then
                  > feed the output of each set through a capacitor and then into the pot.
                  >
                  > Here's a quick scribble (with some guessed values) of one side:
                  > http://www.scotthelmke.com/capsule-mixing.jpg
                  >
                  > Carrying around a parabolic dish you're probably not worried about
                  > adding a small box to get the circuitry right.
                  >
                  > A popular line of capsules here on micbuilders is the Transsounds
                  > capsules; they have some very nice small and medium diameter cardioid
                  > condenser capsules for a few dollars each. The best thing is that they
                  > don't have a built-in FET, which means it's possible to build a much
                  > quieter mic than with the usual Panasonic style capsules such as the
                  > ones you're using. The downside is that they don't have any omni
                  > capsules without the FET.
                  >
                  > -Scott
                • tk7859
                  ... I managed to get out into the garden and do a test today. First a reminder of how the change from the boundary capsules to the focal plane capsules used
                  Message 8 of 28 , Apr 16, 2008
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                    --- In micbuilders@yahoogroups.com, "tk7859" <g0sbw@...> wrote:
                    >
                    > Hello Scott and the Group
                    >
                    > Today I finished making the capsule mixing/power supply unit
                    .........................................
                    > During the next couple of days I will put the unit into a suitable
                    > container and do some field tests. I will post the results on
                    > "micbuilders".

                    I managed to get out into the garden and do a test today. First a
                    reminder of how the change from the boundary capsules to the focal
                    plane capsules used to sound

                    http://ad2004.hku.nl/naturesound/TomR/PRHSB2/wpecker2.mp3

                    and this is how it sounds now (but in this case the move is from the
                    focal plane capsules to the boundary capsules)

                    http://ad2004.hku.nl/naturesound/TomR/PRHSB2/sample1.mp3

                    very smooth now.

                    Again, many thanks to all

                    Cheers

                    Tom Robinson
                  • Bill Gruhn
                    Hi Rick, I would like to add a bit of memory to the early electret topic. I was married in 1962 and set up housekeeping with my new bride in our own home.
                    Message 9 of 28 , Apr 23, 2008
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                      Hi Rick, I would like to add a bit of memory to the early electret
                      topic. I was married in 1962 and set up housekeeping with my new
                      bride in our own home. That tidbit sets the date. While still living
                      in my mother's home (prior to 1962) I saw an small article in one of
                      the freebie electronics engineering magazines describing the electret
                      microphone invention. I was intrigued by the idea so I built a couple
                      of capsules using aluminum stock and machining the body and clamping
                      ring. Then installed an aluminum sputtered mylar diaphragm, connected
                      it up to a high voltage power supply, about 1kv, put the capsule in my
                      mother's kitchen oven, turned on the 1kv and brought the oven up to
                      some temperature around 400F for a few hours, then turned off the heat
                      but left the polarizing voltage connected until everything was back to
                      room temperature. When cool the HI-V was turned off, the capsule
                      retrieved and when connected to a high gain mike stage the little gem,
                      about an inch in diameter actually worked as a microphone. FETs were
                      unheard of in 1962 IIRC. Never took the project any further, but kept
                      the capsule around for many years and found it still working after
                      many years.

                      RGDS,

                      Bill




                      --- In micbuilders@yahoogroups.com, umashankar mantravadi
                      <umashanks@...> wrote:
                      >
                      > dear rick
                      >
                      > i remember reading somewhere that the browin tape sold as
                      'wondertape' is attually en electret film. they apparently charge the
                      film so it does not stick to itself. maybe one should investigate
                      various self adhesive tapes. if one is making a back electret. this
                      tape will be glued to the backplate, so thickness may not matter that
                      much. or does it? i have not thought through this.
                      >
                      > umashankar
                      >
                      > i have published my poems. read (or buy) at
                      http://stores.lulu.com/umashankar
                      >
                      >
                      > To: micbuilders@...: rickc@...: Wed, 2 Apr 2008 02:33:12
                      -0700Subject: Re: [micbuilders] Electret Microphones
                      >
                      >
                      >
                      >
                      > A chance bit of surfing tonight led to the discovery of James West
                      and Gerhard Sessler (Bell Labs) as the inventors of the modern
                      Electret Microphone in 1962.There is more information than is easily
                      uploadable, so I will instead direct you to make your own search:go
                      to:
                      http://depatisnet.dpma.de/DepatisNet/depatisnet?window=1&space=unknown&content=index&action=index&session=c23b66f330d98e8eacf60a7748b2b77a8b95deee133e&stamp=105931or
                      if your browser munges the long link:http://tinyurl.com/25bnlyThis is
                      the German Patent Office's website, English user interface.In the
                      upper left corner, click "SEARCH"Choose "Beginner" as the search
                      mode.In the first field, "Publication Number" Enter US in the smaller
                      of the two fields.In the field, "Applicant" enter "Bell"In the field,
                      "Inventor" enter "James West"In the second (lower) options area, check
                      those options that you want to see in the search results.In the
                      "Results/page" dropdown menu, select 50.Now click the "Start Search"
                      button.The Search results now appear.on the right side of the table,
                      there is an Adobe PDF icon. Click that icon to see the first page of
                      the patent.Once you've done that, there is a link at the upper right
                      that lets you see the entire patent, text, illustrations, and
                      all.Within the body of West's patents, there is some discussion of the
                      process by which electrets are made. You'll also note that the initial
                      patents were actually for earphones, but the patents also mention that
                      by reciprocity, the same principles apply to microphones as well.His
                      most recent patent was granted in 2005, without mention of Bell Labs,
                      so perhaps he has retired. He is still around and doing
                      things:http://www.eetimes.com/showArticle.jhtml?articleID=203100808Now,
                      search for this patent: GB 1333847To do so, reset the patent search
                      page, enter GB in the first field of the Publication Number, and enter
                      1333847 in the next field.Click the "start search" button. This brings
                      up a british patent describing a method of making electrets.The short
                      version of the search is that you need a high-temperature oven
                      (130-150C) and a way to generate a high-voltage electrostatic
                      field.--rick chinnhere is the page that led to finding all of
                      this:http://latimesblogs.latimes.com/kareem/2008/02/dr-james-west.htmlhttp://inventors.about.com/library/inventors/blwest.htmAnother
                      route to the German Patent Office's site is via the AES Historical
                      Committee: http://www.aes.org/aeshc/ (see "Search: Patents of all
                      countries"I prefer this site over the USPTO site because they make it
                      much easier to download the text of entire patents. The Google patent
                      site is also recommended, but it apparently does not extend its
                      coverage worldwide. the UK patent, above, did not resolve when
                      searched for.
                      >
                      >
                      >
                      >
                      >
                      >
                      > _________________________________________________________________
                      > Fashion Channel : Want to know what's the latest in the fashion
                      world ? You have it all here on MSN Fashion.
                      > http://lifestyle.in.msn.com/
                      >
                      > [Non-text portions of this message have been removed]
                      >
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