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DIY Measuring Mic

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  • #16
    Re: DIY Measuring Mic

    I got 6 Panasonic WM-61B capsules (the ones with the pins) from eBay and built 2 mics with the Linkwitz mod. I'll post some comparisons tonight against the Dayton EMM-6, and an EMM-6 purchased straight from Herb Singleton at Cross-Spectrum Labs. By the way, there is very little difference between the Dayton and the CSL plots (1/2 to 1 dB here and there), so this difference matters very little to me, building and measuring in a typical garage.

    Hong
    Some people are addicted to Vicodin. I'm addicted to speaker building.

    The Chorales - Usher 8945A/Vifa XT25TG Build
    ESP Project 101 Lateral MOSFET Amplifier
    LM4780 Parallel Chipamp
    Sonata Soundbar Project
    The Renditions - Active/Passive Towers

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    • #17
      Re: DIY Measuring Mic

      Hong, you rock. I'm really looking forward to those comparisons.

      I did find one other write up here:

      http://www.avsforum.com/t/1328136/me...-2055-audyssey

      the short version is, the linkwitz-modded wm-61a was spot-on with the emm-6 up to 1200hz, above that the author says the wm-61a is "inconsistent". However, looking at the graphs he posted, it's only off by 2db and follows the curve of the emm-6 more or less perfectly.

      What I'm curious about (in my inexperience) is, how significant is a 2 decibel deviation in the measuring mic, when it comes to measuring drivers and designing cabinets and passive crossovers?

      Also, I'm curious how the cma-4544 mic from the OP stacks up against the emm-6 and the wm-61. Especially since the wm-61 isn't reliably available (unless the JLI sub actually works the same way?), but it looks like the cma-4544 is.
      Nonsense. You're only saying that because no one ever has.
      Tarkus of Egypt

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      • #18
        Re: DIY Measuring Mic

        I'm using 4 mics for comparison here:

        1. Dayton EMM-6 with cal file, SN 4565.
        2. Cross Spectrum Labs (CSL) EMM-6 with cal file, SN 5105.
        3. DIY Mic using Panasonic WM-61B, with Linkwitz mod.
        4. DIY Mic using CMA-4544.

        Driver used is a brand new Vifa XT25TG30-04. The reason I used a tweeter is because the plots look identical when measuring woofers, so below 5kHz, all the mics gave me the identical data. Measurements are done in free field, with the mic centered on the phase plug of the tweeter, 1/4" away.

        1. Pic 1 is the manufacturer's FR extracted from the PE site. I looked at this to make sure that my plot comes close to the manufacturer's: dip between 10kHz and 20kHz, and a rise starting at 20kHz.
        2. Pic 2 depicts the measurement by the same mic, serial number 5105, using two different cal files, one provided by CSL, the other downloaded from the Dayton Audio site.
        3. Pic 3 is the comparison between a Dayton mic, SN 4565, and a CSL mic, SN 5105.
        4. Pic 4 is the comparison between the CSL mic and the Panasonic WM-61B with LW mod (no calibration).
        5. Pic 5 is the comparison between the CSL mic and the CMA-4544 (no mod, no calibration).

        Here are my conclusions:

        1. The Dayton calibrations are quite good, so for $48, the mic is great value.
        2. Do you need the CSL calibration? If your mic is not calibrated, then yes, but I wouldn't spend money getting a Dayton mic re-calibrated.
        3. DIY mics are relatively accurate up to a certain frequency. If you need to measure the overall magnitude of your build and deal with the sibilance of your tweeter, you may have a problem with an uncalibrated mic.

        Please let me know if my reasonings are flawed (my wife says that often enough that I am starting to believe her).
        Attached Files
        Some people are addicted to Vicodin. I'm addicted to speaker building.

        The Chorales - Usher 8945A/Vifa XT25TG Build
        ESP Project 101 Lateral MOSFET Amplifier
        LM4780 Parallel Chipamp
        Sonata Soundbar Project
        The Renditions - Active/Passive Towers

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        • #19
          Re: DIY Measuring Mic

          Sounds reasonable to me!

          This is really excellent data, thank you Hong. Also, fwiw, your findings are pretty much the same as other mic comparisons I've found online.

          I've ordered 10 of the JLI-61A capsules. My plan is to build a Linkwitz circuit with a jack for input as well as output, then mod several capsules, so I can compare them to each other, without having to build more than one circuit. I'll also try one or two of the capsules unmodified and see what happens.

          Since my short-term goals are learning the ins and outs of taking measurements and working with the software, and a possible subwoofer build, I think this will serve me quite well, for very little money in! Joy!

          Hong, if I sent you one or two of the JLIs wired up, would you be interested in comparing them to the WM- capsule and / or the calibrated mics?
          Nonsense. You're only saying that because no one ever has.
          Tarkus of Egypt

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          • #20
            Re: DIY Measuring Mic

            Sure hoosier. Glad to help.

            Originally posted by hoosiercheetah View Post
            Hong, if I sent you one or two of the JLIs wired up, would you be interested in comparing them to the WM- capsule and / or the calibrated mics?
            Some people are addicted to Vicodin. I'm addicted to speaker building.

            The Chorales - Usher 8945A/Vifa XT25TG Build
            ESP Project 101 Lateral MOSFET Amplifier
            LM4780 Parallel Chipamp
            Sonata Soundbar Project
            The Renditions - Active/Passive Towers

            Comment


            • #21
              Re: DIY Measuring Mic

              Hello Guys I have purchased Dayton Emm 6. I have downloaded the calibration file.Kindly help as how to use this file

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              • #22
                Re: DIY Measuring Mic

                The file is loaded in the software you use to measure with. Google ARTA and Holm Impulse, download, and install on your PC. The cal file will be used by Arta or Holm.
                Some people are addicted to Vicodin. I'm addicted to speaker building.

                The Chorales - Usher 8945A/Vifa XT25TG Build
                ESP Project 101 Lateral MOSFET Amplifier
                LM4780 Parallel Chipamp
                Sonata Soundbar Project
                The Renditions - Active/Passive Towers

                Comment


                • #23
                  Originally posted by hongrn View Post
                  I still have to fine tune the calibration file, may be do a cal file for woofers and tweeter separately

                  Hong
                  Have you fine tuned the calibration file? Would you be kind enough to share the calibration file for CMA-4544 with us?

                  Thank you.
                  Last edited by milikut; 10-12-2020, 12:37 PM. Reason: Added "Thank you"

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                  • #24
                    Every capsule is different, so one cal file will not match another capsule.

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                    • #25
                      Originally posted by tvrgeek View Post
                      Every capsule is different, so one cal file will not match another capsule.
                      Especially after seven years. Methinks a spambot is among us.
                      Francis

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                      • #26
                        A very advanced one if so. Did not join today, so I suspect a new member.

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                        • #27
                          Originally posted by fpitas View Post

                          Especially after seven years. Methinks a spambot is among us.
                          I am sorry, actually my brother has this board: https://www.adafruit.com/product/1063 (he doesn't need it anymore) and attached to it is the same electret mic hongrn tested and created the calibration file for, so I thought maybe he still might have the calibration file and maybe he might share the same; esp. since Panasonic mics are not manufactured anymore.

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                          • #28
                            And I'm sorry for doubting your credentials. Like tvrgeek said though, a cal is specific for a capsule. I suppose you might get lucky and only be a few dB off at places, but it's hard to know.
                            Francis

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