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Teach me about impedence!

Discussion in 'Bass Amps & Cabinets' started by boston asphalt2, Dec 10, 2010.

  1. boston asphalt2

    boston asphalt2 Official Forum Pain in the Ass

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    I am trying to source new cabs, and the ones I am looking at are 4ohms each, meaning when paired will be effectively a 2ohm load. What happens if I am running an amp that is rated for 8ohm? 4ohm?


    QUICK! I need answers, Ive got the deal of a lifetime at my fingertips!
     
  2. Florin

    Florin Warwick Forum Administrator Staff Member

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    Danger, don't do it!!!

    You can fry your amp.
     
  3. ChTBoner

    ChTBoner

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    Trouble's coming your way!!!
     
  4. Augie

    Augie The Desert Bass-ape

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    I'm sure there is a run through here somewhere, if not there are plenty on line. all the rules are pretty logical (its all physics-might be brain-hurtingly complicated but its all logical). the main rule is always know what load your speakers produce in the configuration you will use, and never load up an amp with something below what it is rated for. If you are lucky you will break speakers. I say lucky because re-coning a speaker is much cheaper than replacing a fused output stage on an amp. I once got my ratings mixed up and it cost me nearly 400 bucks in speakers....which was still better than a rooted 1300 buck amp
     
  5. schlobodan

    schlobodan Warwick Streamer Specialist Good Vibe Sponsor

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    It is all about Power:)

    This is just to help you understand and is true for DC only where one can consider the impedance equal to electrical resistance.

    Electrical Power is the product of Voltage and current

    P=U*I

    Voltage is equal to the product of resistance and current

    U=R*I

    So lets say the voltage in your amp is constant.

    this means if R = resistance goes down I the current must go up

    Exmple:

    10V=4Ohm*2,5Ampere -->25Watts
    if you have only2 Ohms

    10V=2Ohm*5Ampere-->50 Watts

    so you amp's circuity would have to handle double the power.

    so if the amps says I can do 4Ohm it means that it can handle a certain amount of power.

    By going to 2 Ohms you double the load.

    hope this gives the idea

    if not we have electrical engineers here in the forum that can better explain and/or correct me:)
    cheers
     
  6. james brunnning

    james brunnning

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    wire them up to come out 8oms
     
  7. digitalkeule

    digitalkeule

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    Schlobodan, your post explains quite good what happens.

    If you´re interested in the "whole thing" read this:
    Speaker Impedance Explained - Ohms

    Wiring them up to come out 8 Ohms would work well if it´s two 4 x 10s. You´d just have to wire them up
    in serial internally for each to come out 16 Ohms. If it´s a 4x10 and a 1x15 it would be more complex. You´d have to wire them up in serial as well, BUT externally! That means the cable you´ll be building would look very weired, like a web going from amp to cab to cab to amp.
     
  8. Augie

    Augie The Desert Bass-ape

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    plus making a loom to wire two cabs together means you might not be able to use them separately or in different combinations.
     
  9. james brunnning

    james brunnning

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    do the have a way to chain them together to change the out put.i sometime run 4 8 ohm cabs link two to two to drop them to 4ohms them both stacks to the amp the amp has two 4ohm out puts.if the amp has two out puts it might be ok tor run both 4ohm cabs off the amp.but two ohms is bad if the amp isn't ment for it.
     
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