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Understanding sensitivity ratings

Discussion in 'Recording' started by jmm22, Nov 11, 2010.

  1. jmm22

    jmm22 Guest

    I see mic sensitivity ratings that look like:

    Sensitivity: 14.1mV/Pa -37 ± 1.5dB

    How do I interpret these values? if one mic had a sensitivity of 10mv and the next at 20mV, which is more sensitive? Given that my more entry level audio interface probably does not have as much gain as better preamps, what value would be considered fairly sensitive, so I might hunt for mics above this threshold?
     
  2. TheJackAttack

    TheJackAttack Distinguished Member

    Specs are a mixed bag. You want to know how different pieces of gear compare but each manufacturer only publishes the ones that make them look good.

    As far as most entry level interfaces, they will have enough gain for your acoustic recording. Some mic's do take a large amount of gains as a matter of course. Any ribbon requires a lot of gain (I am hitting right at 60dB gain for a stereo pair of Royer R101's on classical concerts). The Shure SM7 requires a fair amount of again but not as much as a ribbon. Your average chinese condenser won't need much at all. In fact the ones I've used I hardly touched the gain knob on the preamp. Good condensers don't need much gain either. They just don't rip your ears apart if you drive them harder. I think the AT2020 you mentioned somewhere is not a bad place for you to start. You might also shoot for an AT4021 at some point too.
     
  3. Big K

    Big K Well-Known Member

    Those cool looking figures can be explaned as follows:
    For, e.g., identifying the input headroom compatibility of a mic you must know he microphone sensitivity rating and the maximum SPL allowed for this model.
    The sensitivity rating is usually the most unambiguous indication on the data sheet. It is rated at 1 kHz and expressed in millivolts per pascal (mV/Pa).
    One pascal is the level of pressure produced by a sound source (loudness level) of 94 dB (94 dB SPL).
    For example, using a sensitivity rating of 20 mV/Pa: When a sound source producing 94 dB SPL hits the microphone, it results in an output voltage of 20 millivolts.
    Sensitivity rating and maximum SPL is, e.g., what you need to calculate the maximum output voltage of your mic....
     
  4. jmm22

    jmm22 Guest

    O.K., so if a mic with a sensitivity of 20mV/Pa gets hit with 94 dB SPL, and a mic with a sensitivity of 10mV/Pa gets hit with 94dB SPL, the former is more sensitive because it produces greater voltage for an equal sound pressure. Is this right?
     
  5. TheJackAttack

    TheJackAttack Distinguished Member

    All things being equal, yes. However, not all companies give the same spec. In your quoted microphone that is:
    14.1mV/Pa at -37dBV (± 1.5dB).

    AKG C414B-XLS is rated: 23 mV/Pa at -33 dBV (±1.5 dB)
    AKG C391: 10 mV/Pa at –40 dBV (re. 1 V/Pa)
    Royer R101 is rated: -48 dB (re. 1v/pa)
    Royer SF24 is rated: -38 dB (re. 1v/pa ±1dB)
    Audio Technica AT4051a: –34 dB (19.9 mV) (re 1V/Pa)

    So you see, it's difficult to just read published spec's and make an educated guess without having used the mic unless you are a math wiz and have good mental imaging skills.
     
  6. jmm22

    jmm22 Guest

    I understand the discrepancies, but thankfully, there appears to be better consistency within any given manufacturer, so it is much easier to compare various models within any one companies product lineup, which is as much as I need at this time. Thanks.
     
  7. ebs1

    ebs1 Active Member

    Conversion of microphone sensitivity (dB re 1 V/Pa) to transfer factor (mV/Pa) and vice versa: http://www.sengpielaudio.com/calculator-transferfactor.htm

    Enter: -37 dB re 1 V/Pa and get the answer: 14.1 mV / Pa

    Many regards ebs
     
  8. Boswell

    Boswell Moderator Distinguished Member

    That's just a conversion of dBV to Volts and vv.

    Most mics are specified in dBV per Pascal (also shown as dB ref 1V/Pa) at 1KHz. You can get example comparative figures from all the mics Jack quotes in his list.

    A mic that produces 20mV at an SPL of 94dB (1 Pa) is twice as senstive as a mic that only produces 10mV under the same conditions. The second mic would need 6dB more gain in the pre-amp to bring the line level electrical output up to the same as the first.
     

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