Help me understand Ohms

Discussion in 'Cabinets & Speakers' started by Kolanti, Feb 23, 2020.

  1. Kolanti

    Kolanti Active Member

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    So I want to switch my two g12t75 speakers from my Marshall 1936 2x12 cab to Creamback 65.

    They are two versions one is 8ohms and the other 16ohms.

    The t75 now are 16ohms.

    What should I buy? Is there any difference in sound?

    Pretty much I don't understand what the impedance is lol.

    What do you suggest?
     
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  2. SkyMonkey

    SkyMonkey Well-Known Member

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    A deeper explanation of Ohms is probably best left to someone other than me.

    For amps you need to know the range of the speaker jacks of your amp.
    A single jack is usually 16 Ohm.
    Then they can range from 16 Ohm down to 4 Ohm.
    The jacks may be switchable between Ohm ratings, or dedicated, like the newer DSL and JVMs.

    Speakers are usually single, paired or quads in a cabinet. Single or pairs in a combo.
    How you wire pairs and quads will determine the total load of the cab or combo.
    Single speaker cabs are solely determined by the speaker Ohms.
    Pairs can be wired in series or parallel.

    Series wiring adds the Ohms of each speaker together for a total load.
    e.g. 8 Ohm + 8 Ohm = 16 Ohm cab.
    You can't wire two 16 Ohm speakers in series because no guitar amp has a 32 Ohm speaker jack.
    The disadvantage of series is if one speaker blows, the open circuit leaves no load on the amp.

    Parallel wiring equals Ohms of the speakers (2x16 Ohm is just 16)/number of speakers.
    e.g. 16 Ohm/2 = 8 Ohms, for 16 Ohm pair of speakers in parallel.
    You can't wire two 4 Ohm speakers in parallel because no guitar amp has a 2 Ohm speaker jack.
    Parallel pairs are safer as if one speaker blows, the signal still runs through the remaining speaker(s).

    Quad are usually wired in a combination of series and parallel to bring the total impedance to the same as each individual speaker (normally 16 Ohms).
    A second switchable option is sometimes all 4 in parallel for a 4 Ohm load.

    So for your 1936 cab I would recommend getting two 16 Ohm Creambacks and using the original parallel wiring in the cab for an 8 Ohm load.
     
    Last edited: Feb 23, 2020
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  3. pedecamp

    pedecamp Well-Known Member

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    If you want plug and play and not have to rewire your cab get a pair of 16 ohm creambacks and pop them in. I dont believe there is any sound difference between 8 and 16 ohm speakers.
     
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  4. South Park

    South Park Well-Known Member

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    Take the time to understand this stuff. Does your amp have a ohm switch. Two 16 ohm in Parallel comes out to 8 ohms. The ohms divide
     
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  5. Nik Henville

    Nik Henville Well-Known Member Premium Member

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    .
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    Ohms is where the 'art is...
    .
    .
    .
     
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  6. JTM1963

    JTM1963 Active Member

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    The G12G75's in your cab are 8 ohms and you want 8 ohms to replace them if you want the info on the back to match.
    The inputs at the back of cab are labeled 16 ohm in mono and 2 x 8 ohm in stereo.
    Two 8 ohm speakers in series equal 16 ohm.
    If you were to put two 16 ohm speakers in your cab and wire them the same you would get 32 ohm in series (mono) and 2 x 16 ohm in stereo. 32 ohm is out of bounds for your amp.
     
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  7. Lance Chambers

    Lance Chambers Well-Known Member

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    Basic survival guide: Never connect a lower Ohm rated cab to a higher Ohm rated amp output.:agreed:

    General guideline: As long as the cabinet Ohms are higher than your amp output you will not damage anything.:fingersx:
     
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  8. Michael Roe

    Michael Roe Well-Known Member

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    Simple...…..replace with the same 16 Ohm.
     
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  9. Valvelust

    Valvelust Well-Known Member

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  10. RLW59

    RLW59 Well-Known Member

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    Everyone else ran with the initial claim that the G12T75's in the cab are 16 ohms each. But that claim came from someone who says he doesn't understand ohms at all.

    If a 2x12 cab is 16 ohms, the speakers can not be 16 ohms each. If the cab is stock with a stereo/mono switching jackplate, 16 ohm mono and 8 ohm each side in stereo, then each speaker is 8 ohms.

    Kolanti, please clarify what you've got. Is the cab stock, and does the label say "mono 16 ohms"? If so, then you need 8 ohm replacement speakers.
     
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  11. ampmadscientist

    ampmadscientist Well-Known Member

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    This is my ohmland, the place I was born in.
    No matter where I ohm, it's in my soul.
    My feet may wander, a thousand places.
    My heart will lead me back ohm, to my Donegal.
     
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  12. Kolanti

    Kolanti Active Member

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    I’m even more confused now haha xD
     
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  13. Musicmaniac

    Musicmaniac Active Member

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    :lalala: Me too!
     
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  14. South Park

    South Park Well-Known Member

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    A parallel circuit the ohms divide a series circuit the ohms add. If un sure measure the jack for ohms.
     
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  15. MickeyJ

    MickeyJ Well-Known Member

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    cant any of you amp dogs explain this?

    ohm was named after georg ohm.

    an ohm is just a unit of resistance.

    think of it as one litre of milk.

    think of it as 1000 meters

    it's just a unit of measurement.

    Someone had to call it something, ohm is perfect because it's just three letters.

    Electricity doesn't pass through conductive things at the same rate.

    The quickness or slowness that electricity passes through whatever it is had to have a unit of measurement labeling it because without that anyone trying to copy a design/design a circuit/ create a thing like a speaker would be screwed.

    For example, the two terminals on your speaker are actually just one wire ( inside the speaker) wrapped around and around something. one speaker which is 16 ohms has that wire as having 16ohms of resistance, another speaker which is rated at 8 ohms only has 8 ohms resistance on that one wire. ( one wire, two terminals , one at each end of the wire.)
     
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  16. MickeyJ

    MickeyJ Well-Known Member

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    do otherwise identical speakers with different resistance ratings sound different if set up with the the correct jack on the back of the amp?

    the answer to this is not clear. Some say yes, some say B.S

    Back your question, you need to buy 2 x 16 ohm speakers for your amp.
     
  17. MickeyJ

    MickeyJ Well-Known Member

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    imagine two straws, one is harder to blow through than the other, one has more resistance, now imagine the air as electricity, and the straw as a wire.
     
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  18. RLW59

    RLW59 Well-Known Member

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    Sorry I 'm a dumbass and misunderstood. I thought all 1936 cabs were 16 ohm. If this is an 8 ohm 1936 then yes it has two 16 ohm speakers.
    --------------------
    What amp and what impedance outputs does it have? Do you ever want to add another cab, running both from the same amp?[/QUOTE]
     
    Last edited by a moderator: Feb 23, 2020
  19. Valvelust

    Valvelust Well-Known Member

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    What is it you're actually wanting to know?

    One way to look at it to help confusion.

    The larger the number the "more resistance" the lower the number the "less resistance" (one's mind would think it should be the opposite) A 4 gauge wire is bigger in diameter than a 16 gauge wire. (Big round straw vs Small round straw)

    Like flow of water per say, if a hole was the size of a large 4 gauge wire it would have less resistance and flow more water than a smaller 16 gauge hole would flow.

    A sewer line pipe will have less resistance and flow more water than a water line pipe.

    Weird analogy but principle somewhat the same
     
    Last edited: Feb 23, 2020
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  20. FracStrat

    FracStrat Well-Known Member

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    “ohms” is not a real word
     
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