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Quick Amp Question about Ohm

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

  1. Chunkyzz


    Mar 1, 2012
    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. 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


    Jul 22, 2007
    Dallas, TX
    What he ^ said, exactly.
  4. +1 ditto
  5. Chunkyzz


    Mar 1, 2012
    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

    Feb 11, 2010
    can you take a picture?
  7. Chunkyzz


    Mar 1, 2012
    of what exactly?
  8. Andyman001

    Andyman001 Supporting Member

    Feb 11, 2010
    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


    Mar 1, 2012
    ok im on it =)
    not sure i can take pics of the transformer but the speakrs i can =)
  10. Chunkyzz


    Mar 1, 2012
    ImageUploadedByTalkBass1358279552.570947. ImageUploadedByTalkBass1358279565.814842.
    2 more 2 come
  11. Chunkyzz


    Mar 1, 2012
    Thats my diy cab
    Speaker info
  12. Chunkyzz


    Mar 1, 2012
    Ohm marking on speaker
  13. Andyman001

    Andyman001 Supporting Member

    Feb 11, 2010
    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


    Mar 1, 2012
    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

    Feb 11, 2010
    to the manual (maybe)


    also is this

    what the back of the amp looks like?
  16. 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


    Mar 1, 2012
    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


    Mar 1, 2012
    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. 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


    Mar 1, 2012
    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