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Mic/Pre vs. Square Wave

Discussion in 'Pro Audio Equipment' started by pindrop, Mar 16, 2005.

  1. pindrop

    pindrop Guest

    I am looking for a new drum mic pre and possibly mics, so I have lately been very interested in transient response. The question came to my mind (albeit more theoretically interesting than practical), what microphone/preamp combination would do the best job of passing a square wave?

    Any thoughts?
  2. Kev

    Kev Well-Known Member

    This is a typical test for a mic-pre or any line level unit.

    For units with transformers this can be a way to check for good termination and damping and ringing.

    the mic itself and square wave ???
    you would first have to make an acoustic square wave.
    ... that sounds like fun.
  3. huub

    huub Guest

    apart from a dead room, i'd say a dpa 4006 or earthworks with earthworks or dpa pre would do the job..
    i guess..
  4. David French

    David French Well-Known Member

    Kev, it's simple! Just get a really odd instrument!


    Try the veal.
  5. mpd

    mpd Guest

    This is one of the best audio jokes I have heard in a while...
  6. Kev

    Kev Well-Known Member

    surrounded by comedians
  7. David French

    David French Well-Known Member

    could be worse...

    could be...



  8. Kev

    Kev Well-Known Member

    CLOWNS !!!!!



    Dave was just just kidding
  9. pindrop

    pindrop Guest

    Let's say that you do have an acoustic squarewave. So traveling through the air is a region of uniform high pressure followed by a region of uniform low pressure with an instantaneous transistion between the two regions. Probably not physically possible at extremes, but I think it would be the most difficult thing for a mic to handle.

    The question remains, is there a microphone that could translate this anywhere close to accurately into an electrical signal? That instantaneous transition would require a very light diaphram, and the region of uniform pressure would require that displacement of the diaphram not acceleration of the diaphram results in electrical current.

    If I am thinking properly, a dynamic mic would be utterly terrible. A ribbon mic could better handle the sharp transitions between pressures but because of the magnetic nature of its mechanical/electrical conversion, I believe it would still require acceleration of its diaphram in order to generate signal.

    That leaves condensers and stuff with which I am less familiar. I know that condenser mics are just capacitors and that the signal is generated by the changing capacitance resulting from the motion of the diaphram (or really because of the changing distance between the two plates). But I don't know exactly how that is done. Somebody help me out, can a condenser mic create a uniform change in current from a uniform displacement of the diaphram? By uniform I mean it moves and then stays at that displacement motinless for a time. I know that the capacitance would change uniformly but I don't understand how the signal is obtained from the change in capacitance. So, I assume that condensers do, in fact, meet that criteria. But I don't know, that's why I'm asking.
  10. Kev

    Kev Well-Known Member

    It;s still has a diaphragm and that diaphragm has weight ...
    so the frequency of this square wave could be an issue.

    Higher leans towards Smaller ... as there is a smaller wave length. ... and probably lighter as it needs to accelerate and change direction at impossible rates ... infinit ???

    A PZM might be in a good configuration to give this a good shake.

    Others wise those laser driven sensor things.
  11. pindrop

    pindrop Guest

    Independent of frequency, the slope on the front end of a square wave is infinite. So, yes the diaphram mass is critical and because it has mass it cannot physically do what would be required of it, but that goes back to the original question, that is, what mic could come closest?

    I forgot about pzm's. Do they typically have tiny diaphrams? I've never opened one up to look.

    The steepness of that wavefront is what got me thinking about this in the first place. So, say that a pzm handles that sharp transition well, that could explain the current popularity in sound reinforcement of throwing a pzm in the kick to capture the "attack" while micing it with a large diaphram dynamic to capture the "thud". I have always thought of the kick drum as the audio equivalent to the broadband pulse--all frequencies at the same time, plus a little low end sustain. The quicker rise time (up to full amplitude) on the pzm could contibute greatly to the ... now I'm just babbling.
  12. Kev

    Kev Well-Known Member

    Yes PZM's do have the small diaphragm/sensor
    mounted close to the flat surface... Boundary Effect

    Some very small capsule test mics like the B&K measurements mic could also give this a fair shake.

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