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Quick Amp Question about Ohm

Discussion in 'Amps [BG]' started by Chunkyzz, Jan 14, 2013.

  1. Chunkyzz

    Chunkyzz

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    Heya guys!
    simple question!
    i have a trace elliot vintage GP11 simple 4 12"
    i think its a 250W,its old late 70's and all the marking on it is gone,vanish,disappeared....

    Since it was 2 heavy i took it apart,so i got a Head(built into a box yes) and 2 cabinets of 2 12".
    the speaker says its an 8 Ohm

    MY 2 Tiny Question are!

    1.Can i use only one cabinet of 2 12"?(its the same speakers as there were before i took them out of the Regular amp)
    for lets say smaller gigs? when there is no room for the 2 cabs.

    2.i might buy a new Head (TC BG250 or the bigger one) and it says on the amp minimum 4 Ohm,can i use my Cabinets?the trace 8Ohm?

    so! can i drive half the amount of Speakers with the same head?
    and can i use my old Speakers with a new Head?

    thanks alot!
    if u did not understand feel free to ask =)
  2. HolmeBass

    HolmeBass

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    You can power an 8 ohm speaker load with an amp that is rated at 4 ohm minimum load. You just cannot go below 4 ohms or the amp will overheat and possibly burn up.

    I am not sure how your original 412 was wired, but if you are saying each speaker is 8 Ohm, than each 212 cabinet is probably now 4 ohms (and your original 412 was 8 Ohms- as a guess). Which would be fine. I don't think you would want to run both of your 212s together anymore though, unless you have a series cable, or you will be running at 2 ohms.

    The confusion is how you are using the term "speaker" - the correct way is each cone is a speaker, all the cones together in a box is a "speaker cabinet" or "cabinet". Calling the entire box a speaker is misleading for this very reason.

    What you really need to do is determine the"nominal impedance" - the ohm rating - of each of your 212 speaker cabinets. If it's the case that each of these cabinets is 8 ohms then you would be ok using just one of them, because running 8 ohms in a 4 ohm minumum amp is ok, or you could use both them, as the two 8 ohm cabinets together would be 4 ohms, still ok with your amp.
  3. RickenBoogie

    RickenBoogie

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    What he ^ said, exactly.
  4. bassmeknik

    bassmeknik

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    +1 ditto
  5. Chunkyzz

    Chunkyzz

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    ok so lets see if i got it =)

    I had a Combo amp with 412 speakers whice i took apart, and made 2 cabinets of 212
    now! on the amp head the huge heavy block(transistor i think its called) is written with a stamp 8Ohm whice means the head is 8 ohm(as far as i know)
    and on each speaker whice is wired in series every amp has a stamp 80hm on them.
    so! what should i do?
    run 212 and its ok? or run all of them together? or go to someone who knows and check the amp?
  6. Andyman001

    Andyman001 Supporting Member Supporting Member

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    can you take a picture?
  7. Chunkyzz

    Chunkyzz

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    of what exactly?
  8. Andyman001

    Andyman001 Supporting Member Supporting Member

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    the speakers and the amp/transformer and any other places where the ohms are marked.

    just so we can all be on the same page. :)
  9. Chunkyzz

    Chunkyzz

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    ok im on it =)
    not sure i can take pics of the transformer but the speakrs i can =)
  10. Chunkyzz

    Chunkyzz

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    ImageUploadedByTalkBass1358279552.570947.jpg ImageUploadedByTalkBass1358279565.814842.jpg
    2 more 2 come
  11. Chunkyzz

    Chunkyzz

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    ImageUploadedByTalkBass1358279602.555920.jpg
    Thats my diy cab
    ImageUploadedByTalkBass1358279620.874742.jpg
    Speaker info
  12. Chunkyzz

    Chunkyzz

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    ImageUploadedByTalkBass1358279643.901153.jpg
    Ohm marking on speaker
  13. Andyman001

    Andyman001 Supporting Member Supporting Member

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    sorry for the wait, I was researching this amp.

    In pic #2, there looks to be just "holes" is this true?

    when in the combo, were the speakers wired directly to the amp, or plugged with a cord?
  14. Chunkyzz

    Chunkyzz

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    thats true,its just holes since the amp was a combo the amp had 2 lines going out from the amp head part to the 412 in a series connection.
    the head section is a 2 piece which is connected together by a cable,the transformer and power socket to the head-plate with the EQ and the vol and so
  15. Andyman001

    Andyman001 Supporting Member Supporting Member

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    to the manual (maybe)

    link

    also is this

    what the back of the amp looks like?
  16. HolmeBass

    HolmeBass

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    I am glad Andyman is on this, because a sentence like this is just confusing. Actually, meaningless. There are no amps on speakers.

    But from the pics the speakers are 8 ohms (the space between "8" and "ohms" helps a lot, doesn't it?) and if you really wired them in series than each of your 212's is a 16 ohm cabinet, and running them together in parallel (the way 99.99% of speaker cabinet jacks and amplifier jacks are wired) then you'll get 8 ohms net.

    If you amplifier can only go as low as an 8 ohm load, this will be ok. If you actually wired the speakers in the cabinets in parallel then you will break your amp.
  17. Chunkyzz

    Chunkyzz

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    lets see if i understand parallel VS series.
    what i did is the the - of the 2 speakers is connected to the - of the Amp Head to the same place together and not Speaker to speaker and then to the Amp.

    got it?
    same for +
  18. Chunkyzz

    Chunkyzz

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    and Yea this is my Amp the one in the pic.
    it was a combo so no Jack connected to the Plate.

    and just to let you guys know, i am not going to connect any other speaker/cab/cabinet other then the ones that was in the combo,lets say i took the combo and splitd it into 3 boxes =)
  19. HolmeBass

    HolmeBass

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    So both negative speaker terminals ( - ) are wired together and to the negative amp terminal, and both positive speaker terminals ( + ) are wired together and to the positive amp terminal? That's a parallel connection!! Have to go right now, will come back later, don't run your amp like that!
  20. Chunkyzz

    Chunkyzz

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    oh ****... i did already play with the amp for 2-3 hours at low Volume... thank god the gig was canceled...
    guess i go to my friend who builds amps and stuff.... to check the things i did... and i will get a punch to the head lol
    thanks!

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