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Electret Condenser Mic Question

Discussion in 'Electronic Repair' started by Spin, Feb 26, 2007.

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  1. Spin

    Spin Guest

    I have a headset electret condenser mic that has a low frequency response.
    Other than changing the element is there a means of getting a higher
    frequency response?
     
  2. Arfa Daily

    Arfa Daily Guest

    Are you saying that the frequency response is poor, as in it is unable to
    respond to high frequencies such as speech sibilants ? If so, that is very
    unusual, as in general, the frequency response of an electret mic is very
    good - certainly more than adequate for speech, and in most cases, good
    enough for pretty much anything short of professional recording. A quick
    look at the specifications of a few shows them to be good to at least 16kHz.
    Has the response always been poor ? Are you sure that the problem is not
    something much more fundamental, such as the small hole where sound gets
    into the mic, being stuffed up with fluff or other clag ? Or are you maybe
    feeding it into an input with entirely the wrong sensitivity / impedance ?
    Does the insert get it's supply from an internal battery, or should it be
    fed with a phantom supply from the equipment that it's plugged into ? If so,
    is the equipment providing such a supply ? Not quite the easy question that
    you were supposing perhaps ... ??

    Arfa
     
  3. Spin

    Spin Guest

    The electret element in question is 400 ohms imp & it was plugged into the
    input of a 600 ohm imp computer sound card. Recording my speech i noticed
    that it lacked "highs". I then replaced the above with a 2k ohm imp element
    & there was a vast improvement. The improvement consisted of a higher freq
    response & a dramatic increase in output (volume). What baffles me is, i
    thought that by matching the mic & sound card with similar impedance that i
    would get better efficiency? It appears that my computer sound card (600
    ohm input ) works better with a 2k ohm mic than a 400 ohm mic! By the way
    the sound card provided the power for both mics. Any comments concerning the
    above would be appreciated.
     
  4. A nominal 600 ohm input won't be 600 ohms but somewhat higher. At one
    time, about 1.2k was the norm for a nominal 600 ohm mic. Which are usually
    about 300 ohms. ;-) A higher input impedance shouldn't effect frequency
    response but might make the noise figures worse. However, too low an input
    impedance will result in a bass loss. Which might sound like a treble gain.
     
  5. Arfa Daily

    Arfa Daily Guest

    I agree with what Dave says, and would bow to his superior knowledge of
    studio audio anyway. Even given the levels of impedance mismatch that you
    think you have, and the somewhat worse ones that Dave says you likely *do*
    have, it still doesn't seem to me to be a sufficiently badly matched system
    to have a such an (apparently) large difference between the two mics. It
    might in the end just be "one of those things" that has no rhyme or reason
    to it. The sound card might simply just not like the original mic.

    Arfa
     
  6. rebel

    rebel Guest

    Just to clear the air, can you confirm that the 2k mic was an electret and not a
    dynamic? From my experience (commercial communications, not studio) the results
    you are getting would be explained by the 2k being a dynamic and the electret
    NOT being powered. BTW, I haven't seen a PC sound card that does power a mic.
     
  7. Jeroni Paul

    Jeroni Paul Guest

    Most PC sound cards mic jack are stereo type and provice supply
    through the center tap.
     
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