Connecting up a 4 ohm cab?

Discussion in 'Amps and Cabs [BG]' started by Rumblebee, Aug 9, 2005.

  1. Rumblebee

    Rumblebee Guest

    Mar 16, 2005
    Okay, probably a stupid question... but, I've got a Hartke amp with two 8 ohm 1/4" speaker output jacks. If I want to hook up a 4 ohm cab, do I have to have both the outputs going into the cab? I ask because the cab I would hook it up to has only one input (a speakon at that, already requiring a cable with a 1/4" on one side and a speakon on the other).

    It seems like I shouldn't have to have both outputs from the amp going into the one input on the cab, but I thought I should ask. Thanks in advance!
  2. Thor

    Thor Moderator Staff Member Gold Supporting Member

    You should be fine with one cable 1/4" male plug to the 8 ohm output of your amp.

    The total load on your amp will then be 4 ohms.


    Check the amp rating ( book or manufacter specs on website), and see if it is capable of handling 4 ohms.
    Or less, like 2 ohms. Most cab specs list what the minimum
    impedance value the amp can run at is.

    Print the specs, as models change, sometimes the old
    specs disappear.

    You are all set to go. :bassist:
  3. Rumblebee

    Rumblebee Guest

    Mar 16, 2005
    Thanks! I definately wouldn't add a second cab. And the amp can handle a 4 ohm load. Again, much appreciated. :bassist:
  4. gwreid


    Apr 8, 2005
    Thor, I'm a little confused by your answer. Are you saying that an amp with two 8 ohm speaker connections can have a single 4 ohm cab on one side but not a 4 ohm cab on each side? This I suppose implies that two 8 ohm cabs connected would be 4 ohms? I know this would be the case if you daisychain the cabs but I had, until now, assumed that if the amp has two 8 ohm connections the cabs in total would be 8 ohms. This is not correct?
  5. Thor

    Thor Moderator Staff Member Gold Supporting Member

    It would be if it was a stereo amp. ie 2 separate and distinct amplifier channels

    If it is a mono amp, and I am assuming that with no info to the
    contrary, the effect of plugging the 2 cabs in into the parallel
    amp outputs is the same as daisychaining them. The manufacter provides 2 outputs as not all cabs have more than one jack. The end result is for two 8 ohm cabs in parallel is:

    r1 x r2
    r1 +r2 OHM's LAW ( for 2 resistors)


    ---- = 4 ohms

    If he just plugs in the load he has on the line at 4 ohms, that is all that is there.

    If he puts two 4 ohm cabs he ends up with 2 ohms and fries
    his head if it is not rated for that.

    If he puts 2 8's he is fine.
  6. gwreid


    Apr 8, 2005
    Thanks, makes sense. Thanks for the Thor point.

    Sorry, couldn't "resist."