Loaner: Mic Calibrator

Discussion in 'Closed Loaners' started by ChaChaRealSmooth, Oct 14, 2019.

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  1. dBel84

    dBel84 Friend

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    A word of caution to anyone who has the Daytom UMM-6, I managed to snap off the mic "boom" while making sure I had a snug fitting adapter. Nothing a little epoxy and duct tape couldn't fix but an unexpected WTF moment.

    This mic has about a 3dB variance at 1kHz from the calibrator.

    now need to figure out how to generate a new calibration file.

    ..dB
     
  2. Luckbad

    Luckbad Traded in a unicorn for a Corolla

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    I've done the general stuff in the original post now and calibrated against 94dB etc. I have no clue how to generate a correction curve for my mic right now, but I'll try to explore that further over the weekend.
     
  3. atomicbob

    atomicbob dScope Yoda

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    The only thing you can learn with the mic calibrator is the sensitivity of your microphone. To create a correction curve requires cross-calibration against another microphone with a known calibration curve.
     
  4. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    FYI, I accidentally left out the physical manual on shipment, but I figure I can return it to @atomicbob. But if anyone needs it before the calibrator makes it back to him, just let me know.
     
  5. Biodegraded

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    Did anybody test at 114 dB as well as 94 dB? Consistent results, or no?

    On quick initial testing, my current calibration is apparently low at 94 but high at 114. But I'm close to full-scale at the latter, which could be part of the problem.
     
  6. Biodegraded

    Biodegraded Friend

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    I had I think a productive time using using this to check my existing calibration of the Dayton iMM-6 microphone I’ve been using with a flat-plate coupler to measure headphones, with a plastic tubing coupler to measure earphones, and with my phone to try to tweak my speaker setup in new surroundings. This might seem dinky for a measurement tool, but I'm pretty sure it uses the same capsule as the popular UMM-6; the specs on Dayton's website are identical.

    When using this mic directly with my computer, I feed it to one of two external USB soundcards: a cheap-as-chips Ugreen dongle and an Audio Technica ATR2 (also cheap). I wanted to have calibrations I could use to find the appropriate input-volume and level settings in REW’s prefs for each.

    I’d recently calibrated the mic and one of the cards using VSLM and a 94 dB file provided by atomicbob here. After setting everything up and making test measurements over a couple of days, the ND-9 settled into a reading 0.4 dB higher than my VSLM calibration. After recalibrating using the ND-9 (see the third post in the earlier thread), to check internal consistency I recorded the calibrator's signal with Audacity and used that in VSLM to compare against Bob’s cal file. The results were within the level of precision/accuracy of all the software & hardware in the system: 94.1 dB for one card, 94.0 for the other.

    Pics & screenshots:

    The diameter of the iMM-6 is 5/16”, so getting it tight in the ½” calibrator aperture (critical, as Bob reported in the earlier thread) required some 5/16" ID / 7/16” OD vinyl tubing and a few winds of green painter’s tape:

    [​IMG]

    [​IMG]

    As measured:

    [​IMG]

    Calibration in REW for the Dayton mic & Ugreen dongle. Note I’m using the software’s default of a digital full-scale sine wave crest being -0.3 dBFS (= square wave crest is 0 dB), hence the -19 dBFS level readings rather than -16. Note also the mains noise spikes; I’ve mentioned this room’s location before:

    [​IMG]

    Recording this same signal with Audacity and using it in VSLM relative to Bob’s BK/Schoeps 94 dB = -16 dB calibration file gives this result: good enough for me!

    [​IMG]

    Thanks @atomicbob for the loan, it was fun and interesting!

    Edit: So if you can't lay hands on a hardware microphone calibrator - use VSLM and atomicbob's 94 dB = -16 dBFS calibration file and you'll be sweet.
     
    Last edited: Jan 20, 2020
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