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Wiring a speaker cabinet 1/4 inch jack

Discussion in 'Amp Central Station' started by jman72, Oct 11, 2018 at 12:27 PM.

  1. jman72

    jman72 Tele-Holic

    794
    Aug 31, 2013
    Central Florida
    Hi everyone,

    This is a simple question (and I've done some research) but just wanted to check before I hook things up. I have converted my '77 Pro Reverb to a head and a 2x12 speaker cab. I want to use a 1/4 inch speaker cable to connect the speaker output of my amp to my speaker cabinet. I'm going to use a Switchcraft mono jack (attached to the speaker cab by an L-bracket) and just wire it up to my speakers in parallel as shown here:

    Speaker Jack Wiring 1.jpg

    Should this work fine? The positive (shown in red) is connected to the jack tip, while the negative (black) is connected to the jack ground? I can just plug in a 1/4 speaker cable between the amp output and this speaker jack and all should be fine? Any suggestions or comments? Thanks!
     

  2. JustABluesGuy

    JustABluesGuy Friend of Leo's

    Age:
    60
    Sep 2, 2016
    Houston, TX
    That looks good, just watch your impedance.
     
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  3. jman72

    jman72 Tele-Holic

    794
    Aug 31, 2013
    Central Florida
    Thanks for the input. When you say to watch my impedance, you mean to make sure that my speaker impedance (as wired) matches my OT for my amp? The OT for the Pro Reverb is matched for a 4 ohm load, so the two 8 ohm speakers wired in parallel should give me the 4 ohm impediance.
     
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  4. JustABluesGuy

    JustABluesGuy Friend of Leo's

    Age:
    60
    Sep 2, 2016
    Houston, TX
    Exactly. It sounds like you have a handle on it.
     

  5. Chunkocaster

    Chunkocaster Tele-Holic

    901
    Aug 10, 2018
    In space with Ziggy
    As pictured in your wiring diagram if those two speakers were 16ohm each the cab would end up being 8ohm right?
     

  6. DougM

    DougM Tele-Afflicted

    Jul 5, 2017
    Honolulu, HI
    Correct. Two speakers with the same impedance in parallel will be half the value of each, while in series it will be double the value of each. Combining speakers that aren't the same impedance in parallel is trickier and requires a calculator. In series though you just add the two together to get the total. So, an 8 and a 4 in series will be 12, but an 8 and 4 in parallel is 2.7.
     
    Last edited: Oct 11, 2018 at 7:35 PM
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  7. Chunkocaster

    Chunkocaster Tele-Holic

    901
    Aug 10, 2018
    In space with Ziggy
    Great, thanks. What do you end up with if you use one 8ohm speaker and one 16ohm speaker combined as above? Is there a way to combine the 8 and 16 to get a 8ohm or 16ohm cab?
     

  8. DougM

    DougM Tele-Afflicted

    Jul 5, 2017
    Honolulu, HI
    I don't think so. An 8 and 16 in parallel will give you 5.3.
     
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  9. Chunkocaster

    Chunkocaster Tele-Holic

    901
    Aug 10, 2018
    In space with Ziggy
    Thanks again. The speaker manufacturers should probably come up with an online calculator. It would make things much simpler.
     

  10. gkterry

    gkterry Tele-Meister

    Age:
    62
    262
    Dec 19, 2014
    Paris, IL
    No. Using one 8 ohm and one 16 ohm speaker, in parallel the impedance would be 5.33ohms and in series it would 24ohms. The impedances add in series and in parallel the formula is
    (sp1 x sp2) / (sp1 + sp2)
     
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  11. Chunkocaster

    Chunkocaster Tele-Holic

    901
    Aug 10, 2018
    In space with Ziggy
    Cheers for that formula Greg.
     

  12. JustABluesGuy

    JustABluesGuy Friend of Leo's

    Age:
    60
    Sep 2, 2016
    Houston, TX
    I used to have exactly such an Ohm calculator app for iPhone, but it quit working with a past iOS upgrade.
     
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  13. Chunkocaster

    Chunkocaster Tele-Holic

    901
    Aug 10, 2018
    In space with Ziggy
    I found a online calculator and apparently if you run two 16ohm speakers in parallel and one 8 ohm in series with those you get 16ohm. Makes sense seing as the two 16ohms are converted to 8 by running them parallel. Unfortunate for me I was interested in mixing ohms for a 8ohm amp.

    http://www.speakerimpedance.co.uk/?act=three_series_parallel&page=calculator
     
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  14. chemobrain

    chemobrain Friend of Leo's Ad Free Member

    Nov 5, 2016
    oakland ca.
    as a dyslexic with short term memory issues, I'm all sorted out now, WRONG!
     
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  15. Chunkocaster

    Chunkocaster Tele-Holic

    901
    Aug 10, 2018
    In space with Ziggy
    :lol:

    That's why I need online calculators. I had troubles learning my times tables back in school too. Pythagoris or algebra? forget about it. Staring out the window at the clouds was my specialty.:)
     
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