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Ohms question

Discussion in 'Amps [BG]' started by bigtexashonk, Jan 11, 2013.


  1. bigtexashonk

    bigtexashonk Supporting Member

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    1 - 8 ohm cab run with 1 - 4 ohm cab + a 6 ohm load. Correct or not?
     
  2. Chef

    Chef Moderator Supporting Member

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  3. Chazinroch

    Chazinroch

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    That's right 2.67 ohms. The lower the ohm number the less resistance. Less resistance draws more power. That why amps rated at 4 ohms start to over heat and/or burn up when paired with a 2 ohm speaker load.
     
  4. bassmeknik

    bassmeknik

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    yep, 2.67 ohms (or 2 2/3 ohms if you prefer)
     
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  6. ThisBass

    ThisBass

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    1 - 8 = -7
    1 - 4 = -3

    - 10 + 6 = -4

    Correct or not?
     
  7. Chef

    Chef Moderator Supporting Member

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    In terms of ohms, that^^^^^^is totally wrong.
     
  8. ThisBass

    ThisBass

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    Appro 3 Ohm

    Unlikely the "average" amount runs below 3 Ohm
     
  9. two fingers

    two fingers You tahkin 'uh me? Yeah, you. You tahkin 'uh me? Supporting Member

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  10. B-string

    B-string Gold Supporting Member

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    No Parallel: RT = (R1R2)/(R1 + R2)
    4X8 / 4+8= 2.6666.......... Rounded to 2.67
     
  11. Kmonk

    Kmonk

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    As already mentioned 2.67 ohms.
     
  12. ThisBass

    ThisBass

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    but

    SQRT(-1) = j [ohm]
     
  13. B-string

    B-string Gold Supporting Member

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    If you would like to rewrite the books be my guest, won't make it correct. Formula and links have been offered.
     
  14. ThisBass

    ThisBass

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    I'm not at school but thinking about the real physics of speakers.

    You can't predict the impedance unless you measure the impedance with a proper frequency band measuring voltage and current.

    Most of the time the impedance calculates a bit above the nominal.
    Depending on EQ settings the impedance varies upwards to higher values (most of the time).

    But, ..so what.
     
  15. ThisBass

    ThisBass

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    That's right, but understanding Formulas is a very different animal

    edit:
    Sorry I was wrong, I tried to tell:

    Adaptation of Formulas
     
  16. Chazinroch

    Chazinroch

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    The OP stated this:

    1 - 8 ohm cab run with 1 - 4 ohm cab + a 6 ohm load. Correct or not?

    But I think they meant this:

    1 - 8 ohm cab run with 1 - 4 ohm cab = a 6 ohm load. Correct or not?

    2.67 is correct.
     
  17. ThisBass

    ThisBass

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    That's not wrong (theoretical) but does not reflect the behavior of a real terms 8 Ohm and 4 Ohm speaker.
     
  18. Chef

    Chef Moderator Supporting Member

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    No.
    one 8ohm cab with one 4 ohm cab = 2.67 ohms, as has been said many times in this thread already.


     
  19. B-string

    B-string Gold Supporting Member

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    Speaker are rated for nominal impedance, the point in the pass-band they present the maximum load on the "amp". This is the figure of concern and a simple resistance formula can apply. In reality speakers have inductive and capacitive reactance (to a much smaller degree) as well.

    IF you limit the "speakers" to a frequency much higher than lowest part of the impedance curve then you will need to calculate that new impedance. From there you can use the same resistance formula to obtain the new load presented.
     
  20. ThisBass

    ThisBass

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    That was meant to be a joke
     
  21. B-string

    B-string Gold Supporting Member

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