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How do I lower the impedance load on my amp?

Discussion in 'Amps and Cabs [BG]' started by Golem II, Jun 5, 2002.


  1. Golem II

    Golem II

    Jan 4, 2002
    Macon, GA, USA
    Let's say I have only one 8 ohm speaker cabinet, but I want to lower the impedance of my rig to four to increase the wattage that the amp puts out. What's the best way to lower the overall impedance without buying another cabinet? Does anyone know of an affordable product (load resistor, dummy load, speaker emulator, etc.) that's ideal for simulating an 8 or 4 ohm resistance load?

    Mainly, I'm asking this because I'm thinking of buying an acoustic image Clarus head, but I'd like to run it at two ohms to get the full 300 watt power output from it. Unfortunately, most small cabs are 8 ohms and I can't afford four of them right now.
     
  2. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    AFAIK there's no reasonable way to do this. I think you'll need to buy a different cab, a different head, or both.
     
  3. bassplayajew

    bassplayajew

    Mar 14, 2002
    Bethesda, MD
    Look for a book called "How to make a speaker cabinet", and from there you're on your own...
     
  4. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    If you added three 8 ohm power resistors in parallel with your cabinet, you'd get 2 ohms (sort of as a loudspeaker's impedance varies wildly with frequency...but we'll assume that you have 2 ohms).

    Your cabinet would get only 1/4 th of the total power (each load element be it resistor or speaker would split the input power equally (assuming that they're all the same impedance)) so it might actually get less than if you just use it alone with the amp.

    The only way to convert the 8 ohm impedance of your cabinet to 2 ohms is with an impedance matching transformer. Peavey might actually offer one on their web site and it would have to be good for at least 300 watts. The cost would be about the same as adding another (used) cabinet (and it wouldn't weigh much less) and you wouldn't reap the benefits of adding additional cone area. If you find a 4 ohm cabinet the total impedance when used with the 8 ohm cabinet would be 2.7 ohms with the 8 ohm cab getting 1/3 of the power and the 4 ohm cabinet getting 2/3.

    Good luck!