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Function generator and impedance

Discussion in 'General Electronics Discussion' started by tpajet, May 29, 2014.

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  1. tpajet


    May 29, 2014
    If I have a function generator and I want to connect it to a speaker, how do I account for different impedances of different speakers so I don't damage the function generator?
  2. BobK


    Jan 5, 2010
    Easy. Put an amplifier between the output of the signal generator and the speaker.

    It is not just a question of impedance mismatch, it is a question of how much power can be supplied. A typical function generator is not designed to drive a speaker.

    KrisBlueNZ likes this.
  3. shrtrnd


    Jan 15, 2010
    What's the model of your function generator?
    Most of what I do is signal processing. I can can get a reasonable output, but have to use a 50 ohm load to match my signal circuit inputs.
    Have you got a manual for your generator, and is it any help?
  4. Arouse1973

    Arouse1973 Adam

    Dec 18, 2013
    What so you connect a 50R load to your sig gen and then what connect an 8R or 4R load across this. If so what's the 50R load doing.
    Thanks Adam
  5. shrtrnd


    Jan 15, 2010
    I guess my point is that what type of function generator you use, matters.
    I referenced my own work in signal processing as an example of my requirements.
    I've never tried to drive a 4 or 8 ohm speaker with one in my work, but the fact that I need an impedance matching load of 50 ohms for my signal processors, indicates the fact that while BobK pointed-out simply
    using an amplifier on the function generator output solves the problem of impedance matching; the make of the function generator for tpajet's application may involve it's own impedance matching issues that
    need to be dealt with when considering the speaker load.
    In my case for example, if I use a HP3325 series function generator to drive ANY signal conditioner output, I need an in-line 50 ohm load at my function generator output.
    My Wavetek 191 has a push-button switch on it, that connects and internal 50 ohm load when I need it for signal processing applications.
    After thinking about it, my input here may not be applicable to tpajet's application; but I suggested he check with the manual for his function generator, to see if he was overlooking any mfgr spec that would affect what
    he's trying to do. My 2-cents worth, for what little value that might be.
  6. tpajet


    May 29, 2014
    It's a JYE Tech FG085. It's a cheapie with a digital display and controls. But from what I've read and seen (review videos) it should be perfectly fine for hobby projects. I haven't put it together yet but soon enough.

    The current project I'm wanting to build a Chladni plate. Here's a video showing what that is:

    I've found projects to build these that you basically take a small bucket or container that's the same size as a speaker and hot glue that to the speaker cone, though I'd think at least a 2 way or 3 way speaker would be in order for that. From the projects I've found on line, they show just hooking up the function generator directly to the speaker, and that's what caught my attention about them not seeming to account for impedance.
  7. tpajet


    May 29, 2014
    Also, being a cheapie it does have a manual to match - thin and not of much help.
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