Running 8 ohm 2x12 with 16 ohm 4x12 -- 2x12 is louder?

Discussion in 'Amps and Cabs' started by phoenix 7, Feb 10, 2012.

  1. phoenix 7

    phoenix 7 Silver Supporting Member

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    I'm running my Shiva into a Germino 4x12 (16 ohm) and a Germino 2x12 (8 ohm). I'm running one 8 ohm output from the Shiva into the 2x12 (open back), and the other 8 ohm output into the 4x12. (I double-checked with Greg Germino and he said this set up is fine.) In this configuration, running both cabs at once, it seems to me that the 2x12 is producing a bit more volume than the 4x12. Does that make sense? Could be some kind of sonic illusion, but the 2x12 really seems a little bit louder to me. Both cabs are running the same Greenback reissues.
     
    Last edited: Feb 10, 2012
  2. Stu Blue

    Stu Blue Member

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    The 8ohm cab will take twice the power from the amp that the 16ohm one does... always... electricity flows to the lower resistance more easily. Your 16 ohm cab is seeing half the output that the 8ohm one does. I'm surprised Greg didn't mention that.

    Edit: This means each speaker in your 2x12 cab is working four times as hard as each speaker in your 4x12... if your impedances were the other way round (8ohm 412, 16 ohm2x12) each individual speaker would see the same load.( Edit Load was the wrong word here... watts output is more correct).
     
    Last edited: Feb 10, 2012
  3. phoenix 7

    phoenix 7 Silver Supporting Member

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    Thanks for the info! One more stupid question:

    I've got an Aracom attenuator that converts impedance. If I ran the signal from the amp's 8 ohm output into the Aracom and converted it to 16 ohms before sending it to the 2x12, would that be safe for the gear (while equalizing overall volume from the cabs)? Sorry - I can never keep impedance theory straight.... (I would continue to run the other 8 ohm output from the amp directly into the 16 ohm 4x12.)
     
  4. Stu Blue

    Stu Blue Member

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    I've no idea. I don't have an Aracom or any attenuator. It is possible to convert impedance. Can't help beyond saying read the manual. The general truth is match amp impedance tap and speaker load, all mismatches impose extra stress on the amp and attenuators frequently impose an incorrect load when used to drop the volume a lot (often as high as 30 ohms at bedroom level).

    Edit What I'm not sure of is whether the Aracom would show the amplifier a 16 ohm load from your 8ohm 2x12 or not.
     
  5. Frank Speak

    Frank Speak Member

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    Attenuators don't convert the impedance for the speakers. They convert it for the sake of the amp. That amp has to see a proper load. Setting the attenuator to 8 ohm and setting the amp impedance selector to 8 ohms makes the amp happy. The speakers couldn't care less what the attenuator and amp are set on.

    DISCLAIMER: I'm not an amp tech so don't try something based on what I tell you.

    Love,

    CPA (aka Accountant)
     
  6. Stu Blue

    Stu Blue Member

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    Just to be clear about things, what the OP wants to do is show the amp a 16ohm load from his 8ohm cab. He's trying to get an equal output from one 16ohm cab and an 8ohm one, running both together (showing the amp a total 8ohm load on an 8ohm tap rather than the 6ish ohms it does now.).

    Whether the Aracom can do this I have no idea.... but his comment about "Aracom at 8ohms and connecting to it's 16ohm speaker connection sounds the wrong way round to me. I doubt that he connect two different impedance speakers directly to the Aracom and get what he wants.

    I assumed he was thinking of just using the Aracom on the 8ohm cab (+16ohm cab direct to amp). I think there would need to be a switch on the front of the Aracom to change the impedance the amp sees (plugging into the "correct 8ohm socket on the back of the Aracom).

    To the OP If you get it wrong you could half the 8ohm down to 4ohm... a very brief test would show a dramatically increased volume of the 8ohm cab v the 16 one...

    EDIT If the amp has a 4ohm tap available it's more likely the Aracom can convert that 16ohm cab down to 8ohm... running the 8ohm cab direct instead...8ohms+8ohms=4ohms.
     
  7. pacomc79

    pacomc79 Member

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  8. The Kid

    The Kid Member

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  9. Structo

    Structo Member

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    Assuming the amp has the output jacks wired in parallel, the 16 and 8 ohm cabs present a 5.3 ohm load to the amp.

    So set the amp to either 4 ohm or 8 ohm.
     

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