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Speaker impedence please??

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by johnnyguitar, Jan 14, 2006.

  1. johnnyguitar

    johnnyguitar Long in the tooth Silver Supporting Member

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    I have a combo with a 8 ohm speaker and a extension cab with a 16 ohm speaker...I have a selector switch on the amp 4-8-16 to choose from...anyone know the best ohm selection for the amp..the amp is a Carr..thanks in advance
     
  2. John Phillips

    John Phillips Member

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    4 or 8 ohms. Either is a safe mismatch - the total impedance is actually 5.33 ohms. I would try both and see which sounds best, and if you can't tell much difference, go with 4 ohms since it's slightly less hard on the tubes.
     
  3. johnnyguitar

    johnnyguitar Long in the tooth Silver Supporting Member

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    Thanks John..you've always been a big help to me and other forum members
     
  4. EADGBE

    EADGBE Member

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    I wouldn't hook them up together because they're not compatible. You could damage your output transformer.
     
  5. John Phillips

    John Phillips Member

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    Sorry, this is plain wrong.

    With such a small mismatch (only 33% either way from 4 or 8 ohms on the amp) the only way you'll risk damaging anything is if it was on the point of failure anyway. While this might be true for a fragile old vintage transformer with degraded wiring insulation, even then it's very unlikely that a mismatch this small would actually cause it to fail where it wouldn't have sooner or later otherwise.

    If you know the rules for combining impedances in series and parallel and stay within 'one step' of the setting on the amp (ie no more than twice or less than half), you can use any combination of speaker impedances you like.

    You may need to consider that the power distribution will be uneven too, but that's only a possible hazard to the speakers - in this case 2/3 of the power will go to the 8-ohm speaker, but since it's the internal speaker for the combo anyway this can't be a risk, and the 16-ohm speaker only needs to handle 1/3 of the power.
     
  6. Damon

    Damon Member

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    Nice post OTM, thanks.:AOK
     

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