Beginners question : wiring speakers in parallel...

Discussion in 'DCC Sound' started by Gary, Apr 12, 2017.

  1. Gary

    Gary Wants more time for modelling.... Staff Member Administrator

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    I wish to wire my loco with two speakers, however, I read that they can be run in parallel, that is from one speaker to the next, just like torch batteries negative to positive and so on.

    Can someone please tell me if the diagram below is correct... :scratchchin:

    [​IMG]

    Cheers, Gary.
     
  2. gormo

    gormo Staff Member Administrator

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    G`day Gary,

    My understanding of wiring in parallel is different to your diagram.

    I would call that wiring in series.

    Wiring in parallel would be wire one speaker as normal and then connecting from speaker one to speaker two with jumps leads from positive to positive and negative to negative. This reduces the load on the output and in effect has the load of only one speaker and will give you maximum volume.

    Wiring in series increases the load on the output and reduces the overall volume. It`s the same a putting in a speaker with a much higher impedance.

    [​IMG]

    Cheers Gormo
     
  3. Toto

    Toto I'm best ignored Staff Member Founder Administrator

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    I'd agree with Gormo there Gary.:hammer:
     
  4. Ron

    Ron Full Member

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    Gormo's right, first picture is 'in Series' second (Gormo's) is defo 'in Parallel' :)
    Ron (Radio Amateur G0IBI)
     
  5. Keith M

    Keith M Staff Member Moderator

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    Before connecting speakers, you need to know the impedance ( in ohms) of each speaker and most importantly, the required impedance for the decoders output. If, for example, your decoder needs an 8 ohm output impedance, then if you have two 4 ohm speakers, you must connect them in series. If you connect them in parallel, the combined impedance will be only 4 ohms, which could destroy the decoders output stage. Assuming you have a matching pair of speakers, or at least both speakers have marked + and - terminals, in parallel, you need to connect the two +ve terminals to one output wire, and the two -ve terminals to the other output wire. In series, one output wire goes to +ve terminal of speaker 1, -ve terminal of speaker 1 to +ve terminal of speaker 2, -ve terminal of speaker 2 to the other output wire. The reason for this is so that both speakers are "In phase" with each other, that is to say that each speaker cone (the moving bit that creates the sound) moves in the same direction, not in opposition to each other.
    Keith.
     
  6. SMR CHRIS

    SMR CHRIS Staff Member Moderator

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    Hi Gary
    It all depends on your decoders audio out put and the speaker type and capacity as to wire in series or parallel
    Your first diagram is series wiring, as Gormo noted and Gormo's diagram is Parralel wiring

    Some MRC factory diesel decoders run 2 x 4ohn speakers in series
    as per the first diagram so add the 2 speakers values, giving a total impedance of 8ohm's

    If in parallel as per Gormo diagram you halve the value of the speakers rating you are using
    Usually you will find say 2 16ohm speakers in parallel 1/2of16 giving at total impedance of 8ohm's

    I think some early Athearn factory DCC fitted models, came fitted with MRC decoders, in the Steamers they had parralel speaker wiring as above the UP Challenger was one having 2 16ohm speakers in the tender
     
  7. Gary

    Gary Wants more time for modelling.... Staff Member Administrator

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    Okey dokey...

    I have two x 8 Ohm 13mm round speakers to go in. The decoder is a MRC 00111704 16 Bit Drop in Alco 244 (1.5 amp capacity with overload/over-voltage protection). it states in the instructions that I can use 8 - 32 Ohm speakers, sizes from 18mm - 28mm.

    I had watch a video where the chap had wire his speakers in using the method I had drawn above, and it sounds wonderful...

    https://www.youtube.com/watch?v=F2vYsCMJe9o&t=600s



    Cheers, Gary.
     
  8. paul_l

    paul_l Staff Member Administrator

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    So you need to connect the 2 x 8ohm speakers in series as per your original drawing to give 16ohm.
    In parallel they would be 4ohm and may damage the decoder.

    Paul
     
  9. jvb

    jvb Full Member

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    paul_l wrote:
    Agreed. Parallel connection halves the ohms seen by the amplifier which, in effect, is a doubling of the load - the amount of signal power that the amplifier has to supply.

    Series connection doubles the ohms that the amplifier sees, and thus halves the amount of power it has to supply
     
  10. Toto

    Toto I'm best ignored Staff Member Founder Administrator

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    Nicely explained JVB makes understanding the theory much easier. :thumbs:
     
  11. SMR CHRIS

    SMR CHRIS Staff Member Moderator

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    Ok Gary if the decoder is rated between 8ohm to 32ohm your combo should be set up as per your diagram series to have a 16ohm result that is mid range for the decoder's capacity :thumbs:
     
  12. Gary

    Gary Wants more time for modelling.... Staff Member Administrator

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    Thanks for the replies, much appreciated. I just need to get my wording right, series/parallel... :facepalm:

    I told you I was no good at this techy stuff ! :avatar::avatar:

    Cheers, Gary.
     
  13. Keith M

    Keith M Staff Member Moderator

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    Found this on t'internet, makes parallel resistance calculations simple (never was much good at maths, especially algebra and formula's!)
    sengpielaudio.com/paralresist.htm

    Keith.
     
  14. SMR CHRIS

    SMR CHRIS Staff Member Moderator

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    Keith M wrote:
    I think this is the link Keith was trying to post.
    http://www.sengpielaudio.com/calculator-paralresist.htm
     
  15. Keith M

    Keith M Staff Member Moderator

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    Yes, that's the one Chris, I'm not too good a posting links either, especially on my iPad!:avatar:

    Keith.
     

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