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  • Accelerometer

    If I were to get a simple accelerometer, like the plastic tape type, for use in measuring enclosure resonances, what would I use for supporting hardware and software to make it work and show graphs, etc?

  • #2
    Read he datasheet. They're just piezo sensors, a sticky mic for a guitar is the same basic device. Wire it up with a protection zener and you can use it as a mic input with REW or ARTA. As a piezo device, you will want to ensure your input impedance is as high as possible to overcome the self-capacitance otherwise the low freq will be rolled off.
    "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
    exactly a Fc 3K for both drivers, anybody can do it." -Xmax

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    • #3
      Thanks. Please realize I am electronically inept.

      Is this a proper device and would the zener just go in series with one of the leads? Any particular zener or are they all the same?

      https://www.digikey.com/product-deta...224-ND/3911239

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      • #4
        Meniscus Audio sells an accelerometer to measure vibration for $22. Not sure of its output level. I am sure that if you call them Mark or Joel will tell you everything they know about it.
        "Everything is nothing without a high sound quality." (Sure Electronics)

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        • #5
          Well that’s about perfect then. Thanks!

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          • #6
            Originally posted by dynamo View Post
            Thanks. Please realize I am electronically inept.

            Is this a proper device and would the zener just go in series with one of the leads? Any particular zener or are they all the same?

            https://www.digikey.com/product-deta...224-ND/3911239
            I'd recommend finding an off-the-shelf solution, possibly the part that Ernperkins suggests, also sticky mics for guitars can be had for about the same price. If you want to roll your own, realize that you are taking on an electronics project and be prepared to spend the time doing the research and self-education to understand what your connecting, how it works and what to expect from it. Your zener question can be answered with a simple google search, something like "zener diode how to" should get you on the right path.
            "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
            exactly a Fc 3K for both drivers, anybody can do it." -Xmax

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            • #7
              Thanks, yeah I’m not looking for a project at all, looking for plug n play.

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              • #8
                I'm not sure any of these are what you would call plug and play. None of these give a calibrated, absolute output. You will get a relative output which will allow you to compare different speaker cabinets or see the effects of making bracing changes, etc. Here's a link showing how to use an accelerometer (in this case an ACH-01 available at Digikey and Mouser). The link uses LAUD as the recorder, but you could use any of the current software programs that generate a CSD plot. Your results will also be dependent on the quality of your sound card of course.

                "Everything is nothing without a high sound quality." (Sure Electronics)

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                • #9
                  Originally posted by ernperkins View Post
                  I'm not sure any of these are what you would call plug and play. None of these give a calibrated, absolute output. You will get a relative output which will allow you to compare different speaker cabinets or see the effects of making bracing changes, etc. Here's a link showing how to use an accelerometer (in this case an ACH-01 available at Digikey and Mouser). The link uses LAUD as the recorder, but you could use any of the current software programs that generate a CSD plot. Your results will also be dependent on the quality of your sound card of course.
                  I have one of those and used it with LAUD, a long, long time ago. Did not find its use of particular enlightenment. When designing and writing the article on my Chameleons hosted at zaph's site, I did some extensive testing of the box as the build progressed. There are four takeaways that I found.

                  One, it is very useful for identifying resonances that may be internal space-related resonances, primarily the specific frequencies (pretty much what Stereophile does). These are related to the internal box dimensions as one would expect.

                  Two, As an uncalibrated device, the magnitudes are only useful for relative indications. There's no way that we as DIYers can change that. Even if one could, I don't see it's usefulness in our application anyway.

                  Three, and this relates to number two above, how it is attached makes huge changes in the measured response. The ACH-01 has a smooth, flat surface. There are a number of ways in which one could attach it, but each method will provide different results. They are all effectively mechanical filtering devices. Two sided tape could be used, but I was only interested in relative levels, so I used a very thin amount of Blu-Tac since tape glue degrades quickly. Blu-Tac probably filtered the high frequencies more than lower ones. But high ones aren't usually an issue with box resonances anyway.

                  Four, and possibly the most relevant, is location. I started in the center of an unbraced box side. Later, after bracing, I tested the same location. Dramatic difference as one would expect since bracing should minimize movement. Did the same with other locations such as points that, when braced, would be roughly in the center of the unbraced region. Even moving the attachment point a small bit or detaching and re-attaching very close by gave results that were all so varied that I gave up.

                  The only result I found after all of the effort was confirmation of what we already know about boxes, baffles and bracing vis-a-vis resonances. I suppose that one could use it to see just how dead a cabinet they've built.

                  YMMV.

                  dlr
                  WinPCD - Windows .NET Passive Crossover Designer

                  Dave's Speaker Pages

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                  • #10
                    Thanks guys I’ll play around with it. Prior to reading the last two messages I ordered the Meniscus one so I will see what I can come up with.

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                    • #11
                      For those with microphones, you could get creative and adapt the end of your measurement condenser mic to a stethoscope (generally available at mechanic shops). This would give you probably just as useful data that you'd get from an accelerometer if all you want to see is the frequencies of resonance and relative amplitude as you test different materials and damping methods.
                      "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
                      exactly a Fc 3K for both drivers, anybody can do it." -Xmax

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                      • #12
                        Following this thread. Have been contemplating doing this myself for a while now and will be good to learn from what you find.

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                        • #13
                          Originally posted by dcibel View Post
                          For those with microphones, you could get creative and adapt the end of your measurement condenser mic to a stethoscope (generally available at mechanic shops). This would give you probably just as useful data that you'd get from an accelerometer if all you want to see is the frequencies of resonance and relative amplitude as you test different materials and damping methods.
                          This is an interesting idea as well

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