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4 x 12 speaker load/ohms/wattage help

Discussion in 'Amps and Cabs [BG]' started by baba, Mar 2, 2004.

  1. Help a brother out...

    This is actually for my guitarist's(gasp) fried cab....just pretend it's for bass. He's adding four new Celestions, 30W, to his MusicMan cabinet. The speakers come in 8 OHM or 16 OHM. Based on my limited knowledge of these things, I'm assuming that 4 new speakers at 16 OHM a piece will give me a 4 OHM cabinet? Is this right? Is this ideal?

    Also, what would be the max acceptable wattage input from his amp?

  2. Saetia


    Mar 27, 2003
    Depends on how you wire the cab, I'm not sure exactally how to wire it, but I know you can yeild a 4 ohm cab with 4 16 ohm speakers as well as 4 8 ohm speakers, it's all in how you wire them together. I have an idea but I will spare you because I will probably fudge some detail and be wrong. But basically depends on how you want to wire them. How many ohms were the original speakers? it would probably be the best bet to wire it the same way with speakers of the same ohmage. Someone will come along and elaborate further on what I've written, until then I guess you get my partial explanation. Sorry, Hope I helped,
  3. Thanks Saetia, that did help. At least I know we can't go wrong with buying either 8 ohm or 16 ohm. He said he couldn't find the ohms of the existing speakers but would look again.
  4. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    Four 16 ohm speakers in parrallel will give you 4 ohms. (16 / 4 = 4)

    With four eight ohm speakers, the closest I could get is 4.8 ohms.
  5. Practically speaking, you can wire four 16 ohm speakers to yield 4 ohms (parallel), 16 ohms (series-parallel), or 64 (!) ohms (series).

    You can wire four 8 ohm speakers to yield 2 ohms (parallel), 8 ohms (series-parallel), or 32 ohms (series).

    You *can't* wire four 16 ohm speakers to yield 2 ohms or 8 ohms, and you can't wire four 8 ohm speakers to yield 4 ohms or 16 ohms.

    If you're sure the speakers are 30 W (for example, the V30, despite its name, is rated at 60 W) the cabinet should handle about 120 W regardless of how you hook it up.

    If your buddy's head is a tube head, you should try to match the recommended impedance if possible. Consult the manual. Some tube guitar heads have switches for different output imedances. Make sure that matches whatever you end up going with for the re-speakered cab.
  6. Sorry guys...your math is wrong.
    You cannot wire four 8 ohm speaker in ANY combination to equal 4 ohms. Four 8 ohm speakers will yeild 2,4 or 32 ohms. Here's the math:
    Parallel circuits: Rt= 1/ (1/R1 + 1/R2 + 1/R3 + 1/R4)
    Series circuits: Rt= R1 + R2 + R3 + R4

    Can't change the laws of physics.
    (unless you are a bumblebee)

  7. Richard,you beat me to it!
  8. Thanks guys! My guitarist will be pleased.

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