A portable rig for measurements on the go

Discussion in 'Measurement Systems and Standards' started by La Cenric, Dec 25, 2016.

  1. La Cenric

    La Cenric Acquaintance

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    Recently I've been playing with this Dayton IMM-06, a tiny $25 calibrated mic that works with mobile devices. Currently on my iPhone 7, I'm using the app called "FFT Plot" by Onyx, though other members use more powerful apps like AudioTools and Spectrum Analyser (by Onyx) for more in-depth factors that I'm not yet interested in. Definitely not a replacement for some of the bigger, more advanced desktop rigs out there, but it does really nice quick-and-dirty measurements.

    How it looks like with the ER4PT

    Very simple vinyl tubing coupler, just enough to fit most IEM tips. I've managed to do some measurements at some audio shops here and there and it has been rather consistent with measurements from Tyll and Marvey, though not without its caveats. A few comparisons below:

    Oriolus MK2: Mine and Marv's
    MEE Pinnacle P1: Mine, Marv's, Speakerphone's
    Etymotic ER4XR: Mine and Marv's

    My observations:
    Seems like the IMM-06 with vinyl tubing is rather accurate from 20Hz to 2000Hz, though it gets a little iffy from there. Especially in the range from 5K to 10K, where the SPL it measures seems to be consistently lower than expected. Perhaps some compensation in that area would be better.

    At any case, this setup serves as a great way to do some pseudo-objective comparisons on the go. May not be the most accurate, but can definitely produce an FR curve that shows an IEM's general tonality.

    The rest of my measurements (currently compiling a written list for easier navigation)
     
    Last edited: Dec 25, 2016

  2. Serious

    Serious Friend

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    This looks pretty interesting. Looks like you already measured a bunch of IEMs. Do you think those curves match your subjective impression?
    It's even more portable than my WM-61A rig. Question is what kind of SNR and distortion you can get with this microphone. I've found that even two WM-61As can have different amounts of distortion.
    Part of it could be the microphone, but I think most of it is the tube diameter and insertion depth.

    BTW: Your Oriolus MK2 link links to the Pinnacle P1.
     
  3. La Cenric

    La Cenric Acquaintance

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    Fixed.

    The curves sometimes do match my own subjective impressions (I'm not perfect after all), though some IEMs (like the Rhapsodio Galaxy) I enjoyed more than what I would've expected.

    The FFT Plot app that I'm currently using can only output FR curves. There are more powerful apps out there that can measure THD, like Audiotools. Currently, I'm more interested only in FR curves so I decided to go the cheaper route for now.
     
  4. shotgunshane

    shotgunshane Friend

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    How much vinyl tubing did you use? I'm assuming an amount equal to 2cc? Where can you pick up the tuning? I wouldn't mind playing around with this.
     
  5. La Cenric

    La Cenric Acquaintance

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    I have a few lengths of tubing that I got from my neighbourhood hardware store. I just ensure that there's around a 12mm space from eartip to mic face with every measurement. Perhaps some changes for deep inserts or shallow insert IEMs like the ER4 and T8iE respectively.

    The tubing I use has an inner diameter of 8mm, which snugly fits into the mic nozzle without need for acoustic putty or blu tack.
     

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