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Easy Math Free Impedance (Ohms)


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  • #46
    Just let me know when you think it's ready.
    1/3 solid knowledge, 1/3 common sense, 1/3 made-up bull****************
    Living fossile from a dead world


    • #47
      Originally posted by lug

      You're gonna need a preamp with that.

      See part 6, paragraph 2.
      Girl, I wanna take you to a gay bar


      • #48
        Originally posted by Nate42

        See part 6, paragraph 2.

        Drats! Caught not doing my homework again!
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        • #49

          Well, this about wraps it up. Turned out a little longer than I'd hoped, it takes awhile to explain all the common questions you see with this stuff. But despite its length I hope I've stuck with my goal of keeping it simple, the concepts aren't hard, just stick with it and you'll get it. In summary:

          Don't run your solid state amp at a lower impedance than it is rated for.

          If you connect two or more speakers to one amp (or one channel of a stereo amp) they are in parallel.

          Match your tube amp exactly to the cab impedance it is expecting.

          If your speakers are distorting, turn down. 'Underpowering' is a myth, and turning down is NEVER a bad thing.

          Your impedance rating doubles if you run a stereo amp in bridged mono, so be careful.
          Girl, I wanna take you to a gay bar


          • #50

            Here's some extra stuff that, while not essential, is probably worth mentioning.

            What was that formula for impedances in parallel? 1/Ztotal = 1/Z1 + 1/Z2 + ... , this can be extended for as many impedances as you want. Example 1/8 + 1/4 = .375, so Ztotal = 1/.375 = approx. 2.67. So 8 in parallel with 4 is 2.67.

            What about wiring in series? If you know a thing or two about electronics, you know there are two basic wiring schemes, series and parallel. When impedances are in series they simply add, 4ohms + 4ohms = 8 for example. However, you don't really need to worry about this unless you are making your own cab. Individual speakers within a cab might be in series, but we're normally just concerned with the total impedance of the cab, and multiple cabs on the same amp are always in parallel. You could concievably make a special cable to connect two cabs to the same amp in series, but this is rarely done and not something novices should concern themselves with.

            I've got a multimeter, why doesn't my cab show the right ohms? Simple multimeters measure DC resistance, which is only part of the story when you're talking about impedance. It is completely normal for a cabinet to have a resistance measurement less than its total rated impedance. So if you measure your 4 ohm cab at 3 ohms, or your 8 ohm cab at 6, or whatever, no need to be concerned. Making an accurate impedance measurement requires more equipment and know how than the average joe can be expected to have, that's why the manufacturer makes those measurements for us.
            Girl, I wanna take you to a gay bar


            • #51
              bump. Jazz, I think i'm pretty much done here if you want this to go in the faq. Unless anyone has a suggestion of something to add/change that is.
              Girl, I wanna take you to a gay bar


              • #52

                This is all incredibly valuable information. Thanks for this post!