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2 four ohm cabs equal 2 ohms.

Discussion in 'Amps and Cabs [BG]' started by FleaisGod, Mar 6, 2001.


  1. FleaisGod

    FleaisGod Guest

    Jun 18, 2000
    Atlanta, GA
    If i want ot use two four-ohm cabs, will they work with an amp that doesnt support 2 ohms?

    -Rob/Woody/Fleaisgod
     
  2. oo0o00o0oo

    oo0o00o0oo

    Apr 30, 2000
    Chicago
    Nope
     
  3. FleaisGod

    FleaisGod Guest

    Jun 18, 2000
    Atlanta, GA
    cool, thanks.
     
  4. pkr2

    pkr2

    Apr 28, 2000
    coastal N.C.
    Sure they will. Two 4 ohm speakers wired in series equals eight ohms. Nearly all amps can run into eight ohms.

    Pkr2
     
  5. I'm certainly no expert on this matter but in the time i've been here at TB i've picked up a few things and I belive you have it bacwards P. Two 4 ohm cabs equals 2 ohms. I'm pretty sure about that too.[​IMG] But as always, I could be wrong.
     
  6. Belair is correct, the more speakers you connect, the greater the load on the amp, and the more the
    ohmage drops. -ex. 8 ohm X 8ohm = 4 Ohm Load
    8 0hm X 4 Ohm = 2.67 ohm load,and so on. If you try to drive a 2 ohm load into an amp that doesn't support two ohms,
    it's a sure ticket to meltdown city.
     
  7. danhei

    danhei

    Jan 21, 2000
    pkr2 is also right. If you run the cabinets in series there will be an 8 ohm load. However, you generally need to make a special cable to do this. Almost all jacks on the backs of amps are wired in parallel which would make a 2 ohm load in this situation. Making a series cable isn't very difficult but you would get less power than the amp is capable of supplying to 4 ohms so it's a trade off.

    Dan
     
  8. I think you are talking about wiring the speakers in series. I never heard of a series cable,and I can't see how it would work if the speakers were already wired in parallel.
     
  9. danhei

    danhei

    Jan 21, 2000
    Individual speakers inside cabinets can be wired in series or parallel. In fact, a standard 4X10" cabinet has both series and parallel wiring for the speakers inside of it. In the same manner, two speaker CABINETS can be hooked up in series or parallel. Almost all jacks on the backs of amps are wired in parallel. This does not mean that series wiring of cabs is impossible. One just needs to construct a special cable to do this. I believe one of the more recent Bassplayer Mags has instruction on how to do this.

    Dan
     
  10. bent23

    bent23 Guest

    Jan 3, 2001
    Memphis, TN
    I have an ADA Bassline XV cab 8ohms 250w(2x10,2x5) that has an 8 ohm input, and 2 extension jacks, (one parallel, one series). Can I use the series jack with a standard speaker cable to hook another 8 ohm cab into it and run the ADA into a 4 ohm amp?
     
  11. Christopher

    Christopher

    Apr 28, 2000
    New York, NY
    Bent:

    Based on what you've said, plugging the second cab into the parallel jack will present the amp with a load of 4 ohms; this should work just fine.

    Plugging the second cab into the series jack will present the amp with a load of 16 ohms; not very efficient, but you won't blow up the amp.
     
  12. pkr2

    pkr2

    Apr 28, 2000
    coastal N.C.
    I stand by my original answer. Two 4 ohm speakers in series results in a total load of 8 ohms. Two 4 ohm speakers in paralell = 2 ohm load.


    Yes a special cable must be used to accomplish this but it ain't rocket science.

    Ohms law is a very basic, easy to understand formula for series / paralell connections. Spend about ten minutes learning Ohms Law and it becomes very clear. It's worth anyones time to learn if you are going to be dealing with speaker connections. May even save your amp.

    Hope this helps,

    Pkr2
     
  13. bent23

    bent23 Guest

    Jan 3, 2001
    Memphis, TN
    You know, I knew that.... I don't know what I was thinking. I guess I meant running two 8 ohm cabs parallel into my 4 ohm amp. Which gives me a 4 ohm load, which I can do safely and get the most out of my amp.
     
  14. pkr2

    pkr2

    Apr 28, 2000
    coastal N.C.
    "I think you are talking about wiring the speakers in series. I never heard of a series cable,and I can't see how it would work if the speakers were already wired in parallel." Qt. Reedo.
    ========================
    The fact that the individual speakers, irregardless of how many speakers, speaker impedence or wiring scheme, has nothing to do with the answer. The fact that some combination gives a total impedence at the jack of 4 ohms is the only consideration. The same as two discreet, individual resistors.
     
  15. alx564

    alx564

    Jul 31, 2000
    Emmaus, PA
    OK, I am rather stupid when it comes to amps. I know Ohm's Law but I don not understand how you got 8 Ohm X 4 Ohm = 2.67 ohm load. Could you please explain this to me.
     
  16. Oysterman

    Oysterman

    Mar 30, 2000
    Sweden
    The sum for resistance with resistors connected in parallell (or series? I always mix those up):
    1/R = 1/R<sub>1</sub> + 1/R<sub>2</sub> + ... + 1/R<sub>n</sub> for n resistors.

    Following this formula, it is:

    1/R = 1/8 + 1/4 = 3/8 => R = 8/3 (~ 2.67 in decimal format)
     
  17. alx564

    alx564

    Jul 31, 2000
    Emmaus, PA
    Thank you so much Oysterman!!! I have been searching the forums for about an hour looking for any information on the subject. It is really hard to go through 1,000 different post. Thanks a lot for the help.
     
  18. Oysterman

    Oysterman

    Mar 30, 2000
    Sweden
    Anytime, alx! That's just about all the physics I know... heh... :D
     
  19. pkr2

    pkr2

    Apr 28, 2000
    coastal N.C.
    Reedo, your statement is both correct and incorrect. The load on the amp increases with the number of paralell resistors(cabs). However the load decreases when you add units of resistance(cabs) to a series circuit.

    Plug a cable into each of two cabs with the ends of the cables stripped. Each speaker cable has a red wire and a black wire.

    The speaker cable from the amp has a red wire and a black wire. Connect the red wire from the amp to the red wire of speaker A. Connect the black wire from speaker A to the red wire of speaker B. Connect the black wire from speaker B to the black wire coming from the amp.

    The whole thing can be built in a metal box from radio shack.

    Pkr2
     
  20. MJB

    MJB

    Mar 17, 2000
    Yes that would be parallel, in series you simply add the resistor values. And, if you are dealing with only 2 resistors in parallel, this math is easier...R1xR2/R1+R2 so....

    8x4/8+4 = 32/12 = 2.67