ohm question

Discussion in 'Archived Threads 2001-2004' started by ThomasL, Mar 1, 2002.

  1. ThomasL

    ThomasL Supporting Actor

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    Hi, I tracked down the manual for my Radio Shack "high power 4 speaker selector" switch box and it states the following ohm rating that the receiver/amp will see when certain combos are chosen:
    A or B or C or D = 8 ohms (this makes sense to me)
    A and B = 16 ohms (not sure how this works)
    A and C, A and D, B and C, B and D, C and D = 4 ohms (this makes sense to me)
    A and B and C, A and B and D, A and C and D, B and C and D = 5.3 ohms (not sure once again)
    A and B and C and D = 8 ohms (once again not sure)
    I'm not much of an engineer unfortunately. Can someone explain to me how Radio Shack has internally wired this so when choosing A and B, the amp only sees 16 ohms. I assume from this that the explanation for the ratings on the other pairings above will fall into place. I hope someone is an ohm expert out there [​IMG]
    And if you have any recommendations for a replacement of this switch, that would be good too. I don't know how good a quality it is but I do know it's so light that the speaker wire hanging off the back of it wants to pull it out of the entertainment center and onto the floor.
    thanks much,
    --tom
    -t-om
     
  2. ThomasW

    ThomasW Cinematographer

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    Thomas

    If you have 2-8 ohm speakers and they are wired in parallel the resulting load is 4 ohms.

    If they are wired in series the load is 16 ohms.

    If you parallel a 16 ohm load with a 4 ohm load you get 5.3 ohms

    Hope this helps
     
  3. ThomasL

    ThomasL Supporting Actor

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    Thanks Thomas. I guess I need more education since I'm a little murky on what "wired in series" means. I understand the parallel setup.

    Also, if they are wired in series, how does this affect the resulting volume levels of the two pairs of speakers?

    thanks much!

    --tom
     
  4. ThomasW

    ThomasW Cinematographer

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    Parallel is + to + and - to -

    Series is - to + to - to +

    Amplifiers usually put out less power with 16 ohm loads. So the output level might be lower
     
  5. ThomasL

    ThomasL Supporting Actor

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    Thanks for the help. It all makes sense now - for once [​IMG]
    I replaced the Radio Shack switch today with a Niles 4 speaker selector switch. The Niles is wired in parallel with a manually activated 2.5 ohm resistor for use when you want to drive 3 or 4 pairs at the same time. I had actually tried to replace the Radio Shack one last weekend with an Acoustic Research 4 speaker selector but it had automatic impedance amplifier and speaker protection circuitry that seemed to be either malfunctioning or not working as expected. I decided to return it and get one that had the ability to turn such protection on and off. So far, so good and the new one doesn't want to slide out of the entertainment center either.
    cheers,
    --tom
     

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