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Problems with Ohms

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  • Problems with Ohms

    I currently own a Onkyo stereo receiver TX-8222, and I want to hook up four speakers into one channel of output. According to the manual it says the ohms can be 8-16 when using both channel (which is what I plan to do), but I have two different ohms in each of the pair of speakers. One pair is 8 ohms, while the other is 4 ohms. I want to know if I can combine the two left speakers into one and plug into the left output and the other two right into the the right output. I don't know a lot about sound and ohms, but on what I've read I feel like this should work. Since the combined ohms will be 12 for each output which matches what the manual says. Please comment to help.

  • #2
    Well the short answer is yes but assuming a few things
    Lets call the 8 ohm box "8A" and the 4 ohm box "4B"
    These have to be in series to make 12 ohms.
    ie The positive terminal of 8A connects to the amp.
    The negative terminal of 8A connects to the positive terminal of 4B.
    The remaining negative terminal of 4B connects to the negative terminal of the amp.
    This is the same for both Left and Right.

    Without going into phase cancellations etc with this setup there are 2 main points I can think of that could be problematic.
    The 4 ohm box will hog the power and appear louder than the 8 ohm box.
    (Speaker efficiency may alter that.)
    There is a possibility that the speakers are wired reverse polarity to each other.
    ie a positive voltage at the positive terminal of the speakers may move one forward while the other moves back (out of phase).
    You may be able to tell by connecting a small battery (1.5v) across the speaker and observe if the cone moves in or out.

    The other way is to set it up as described and using one channel (select mono and rotate balance control to one side) and listen to the bass response.
    Then on that one side reverse the connections from one of the series speakers.
    so now
    The positive terminal of 8A connects to the amp.
    The negative terminal of 8A connects to the negative terminal of 4B.
    The remaining positive terminal of 4B connects to the negative terminal of the amp.

    Listen to the bass response again... if it is less than the first way change it back to the original wiring ..ie the speakers are wired the same.
    If there is more bass response one leave it like this ..it means the speakers are moving in and out together correct polarity or "in phase".

    If they (8A & 4B) are going to be in seperate rooms don't worry about the polarity apart from
    the left and right channels being the same. Bass cancellation will only occur if the different boxes are near each other.
    Hope that answers your question.

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    • #3
      Is it possible to connect them in parallel?
      As in connecting the "8A" and the 4B negatives together and connecting to them to the amp.
      And both the positives together to the amp.
      Is this possible?

      Comment


      • #4
        No because the lowest impedence the amp can connect to is 8 ohms.
        So if you connect the 4 ohm speaker first before paralleling them you have already
        loaded down the amp too far before adding even more.
        8 + 4 in series = 12
        8 + 4 in parallel = 2.6666666666666666666666666666667

        Probably be louder with just the 8's.

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        • #5
          thank you
          Well the 4 ohm is a speaker
          and the 8 ohm is a subwoofer
          I might just buy another amplifier.

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          • #6
            Just to get this right.
            I connect the 8a positive to the amp. The 8a negative to the 4b positive?
            Then the 4b negative to the amp?

            Comment


            • #7
              Yes You have to end up with a negative lead and a positive lead.
              Think of it like connecting batteries in series in a torch.
              The positive of the first battery goes to the globe.
              The negative of that battery goes to the tip or positive of the next battery and so on
              till eventually the negative of the last battery goes to the other connection on the globe.
              When you look at a torch all the batteries in series face up the same way with the positive
              at the top and the negative at the bottom.
              They all have to add or work together the same way.

              AMP+.........+8A-..........+4B-.........-AMP

              Usually a subwoofer is independantly powered incorporating a hi cut/low pass filter.
              That enables a balance to be set between the main program speakers and the subwoofer.

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