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2 Speaker Jacks to 1 cabinet. Am I an idiot or what??

Discussion in 'Amps and Cabs [BG]' started by Buzz Fluhart, Sep 29, 2008.


  1. Buzz Fluhart

    Buzz Fluhart

    Jan 10, 2008
    I need y'alls help please. My trusty 1981 Randall Bass 500 head finally broke down, so I am borrowing a friend's Laney head. The Randall's speaker jacks are 4 ohms each, and my cabinet is 4 ohms, and everything matches up. BUT, the Laney's speaker jacks are 8 ohms each. The Laney head prodices 200 watts and my cabinet will handle 800, so wattage issues aren't a problem. I would like to have the ohms match up, just to be safe, so my questions are (don't laugh too hard): Can I run a "Y" cord from both speaker jacks, into the one cabinet? Will this make the output from the Laney head 4 ohms? If I do this, will it make me sound like the thunderous God of Bass I am in my head, or will the system be fried, like the egg, bacon, and hashbrown breakfast I had this morning? Many Thanks for your help, fellow musicians.
     
  2. I don't think that it will be a good idea ... running a 4 ohm head with a 8 ohm cab is no biggie. Troubles start only when the load (ohm) of the cab is lower then the minimum load of the amp.
    I don't know what will happen when you do what you suggested but my guess will be taht at the end of the day something will be broken.

    The other input jack on the cab can be used to connect to another cab of 8 ohm, which gives you a load of the wished for 4 ohm!
     
  3. ehque

    ehque

    Jan 8, 2006
    Singapore
    Your cab is 4 ohms, but your head will only go down to 8?

    You may need to rephrase your question. You have Laney speakers? or a Laney head? or the speaker outs on the head? or both?
     
  4. Rune Bivrin

    Rune Bivrin Supporting Member

    Oct 2, 2006
    Huddinge, Sweden
    If the Laney has two 8 ohm jacks, that means the head can handle two 8 ohm cabinets in parallel, which equals 4 ohms. So you're safe.
     
  5. you really need to tell us exactly what it says on the head .. if as rune is assuming that you have two outlets on your mates head that will both run at 8ohm and they are wired parallel then it will run down to 4 ohm but if they are wired in series then when you plug two 8 ohm bins it runs at 16 ohms .. so if you plug one 4 ohm in your stil gonna screw the head .. so I'm guessing somewhere there it is gonna say minimum ohms .. thats what your looking for .. if it is 8 then your a no go ..
     
  6. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The output does not have an impedance, the speaker does.
     
  7. herndonbassist

    herndonbassist Low Down Thumper Supporting Member

    Apr 7, 2005
    Herndon, VA - NoVa
    If I'm reading this correctly, you'll fry the head. If someone with a TON of knowledge would like to correct me, please do, but I believe that this is going to be a very bad thing, as the current will wind up flowing BACK into the head, as the "'Y' cord" is going to create a circuit from the head and back again. Be that as it may, billfitzmaurice is correct, the amp doesn't have an impedance. Regardless what the amp says, by plugging in a 4ohm cabinet to the speaker jack (using just 1 speaker jack) the amp is going to see 4ohms. If it cannot safely operate pushing 4ohms, you're going to burn out the head.

    You should really read the sticky FAQ on impedance (Amps FAQ *** Now with added info on OHMS and PORTABLE RIGS ***), and also check out this link where you'll find a ton of useful knowledge. IMHO ... DO NOT hook this up the way you're talking about without being VERY clear with what you're doing.

    :D
     
  8. toobalicious

    toobalicious

    May 6, 2008
    triad, nc
    no, but it does have a "minimum" impedence, and this is obviously what the OP is asking about.
     
  9. really depends on the head. does the head hgave 2 separate amps (biamping ability) or just 2 8 ohm jacks, which are probably parralel. is it tube or solidstate? if its 2 8 ohm taps in paralell then it would be perfect to plug a 4 ohm cab into a single 8 ohm tap.

    if you have a multimeter, plug 2 speaker cables or instrument leads into the 2 8 om taps. measure the resistance across the hot (tip) of the leads. if the resistance is 0-5 ohms, they would be in paralell, making it ok to plug a 4 ohm cab into it.
     
  10. Lowbrow

    Lowbrow Supporting Member

    Apr 22, 2008
    Pittsburgh PA!
    Short answer:

    Do not plug an 8-ohm output into a 4-ohm speaker.
     
  11. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The way I read it his assumption is that since the jacks are labeled 8 ohms that paralleling both jacks will result in a 4 ohm output. The likely reason the jacks are labeled 8 ohms is because it's designed to be operated with two 8 ohm cabs, which provides a 4 ohm load. All that would be covered in the owners manual of course, but...:rollno:
     
  12. toobalicious

    toobalicious

    May 6, 2008
    triad, nc
    true, true.....
     

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