Ohm ratings for guitar amp / extension cab

Discussion in 'Amp Central Station' started by EdM123, Jul 23, 2016.

  1. EdM123

    EdM123 NEW MEMBER!

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    I have a guitar amp that recommends the following for connecting to an external cabinet:

    Only use extension cabinets with an impedance of 8 Ohms or more (e.g. 16 Ohms). NEVER use a lower impedance (e.g. 4 Ohms) or damage could result. WARNING: If you use an extension cabinet with an impedance of more than 8 Ohms your Pathfinder 15/15R’s output power will be reduced – it only produces its full output of 15 Watts when presented with an 8 Ohm speaker load.

    I have been offered an extension cabinet described as having "Impedance - Switchable 4/16 Ohms mono or 2 x 8 Ohms stereo." The cabinet has two inputs labelled 'input' and 'link'.

    Please could someone tell me:

    1) Can the speakers in the cabinet be setup such that the cabinet will be 8 ohms running off the one input (my amp)?

    2) If the above is not possible and the cabinet is 16 ohms, will I lose a lot of power by running the 8 ohm amp into it?

    Thanks
     
  2. DeweyPeek

    DeweyPeek Tele-Holic

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    1) no
    2) I don't know

    Is it a combo amp? You might be able to use just the cab if you unplug the combo speakers
     
  3. EdM123

    EdM123 NEW MEMBER!

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    It's a solid state combo. When an extension cab is connected, the combo's speaker is automatically switched off.
     
  4. RLee77

    RLee77 Friend of Leo's

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    That extension cab has two 8 eight ohm speakers (if it's a 2x12), or four 16 ohm speakers with 2 separate parallel pairs (if it's a 4x12).
    So no, you can't have all the speakers connected as an 8 ohm load. It's either 4 or 16. You can just use half the speakers and get 8 ohms.

    No idea how your power would change, that depends on the impedance of your output stage.
     
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  5. soulman969

    soulman969 Telefied Ad Free Member

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    2) You will lose some out put if you run a SS amp designed to run at 8 ohm at 16 ohms.

    1) Yes, it would seem to if it's advertised to run at 8 ohm each in stereo the question is which input is the correct one for that. My guess is it's the one labeled "input" since "link" would seem to indicate the that two 8 ohm speakers are being combined to run it either 4 ohms or 16 ohms.

    Where it the switch that's mentioned that controls that?
     
  6. SolidSteak

    SolidSteak Friend of Leo's

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    1) You can't get BOTH speakers to 8 ohms, since they are EACH 8 ohms. But 8 ohm stereo probably means you can use one of the two 8 ohm speakers and the other speaker will just sit there. (At least I -think- that's what it means... I have seen 2x12's, 4x12's and 4x10's set up that way.)
    2) It may or may not be that noticeable, but think of it this way: either way it will probably sound louder than the 1x8 speaker in your Pathfinder.
     
  7. AlbertaGriff

    AlbertaGriff Tele-Afflicted

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    Get an 8 ohm cab.
     
  8. johnnyha

    johnnyha Tele-Afflicted

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    Yeh don't mess around with it, it's the wrong cab for you, a compromise - get a 2x12 cab with 2 16ohm speakers in series for 8 ohms. Or get a 1x12 with one 8 ohm speaker. Or even a 2x12 with two 4 ohm speakers in parallel which actually might give you the best possible tone.

    EDIT: As pointed out I got this backwards series v parallel.
     
    Last edited: Jul 24, 2016
  9. irie

    irie Tele-Holic

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  10. buddhuu

    buddhuu Tele-Meister

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    I think that's reversed. 2 x 16 ohms in series would give 32 ohms. You'd want 2 x 16 ohms in parallel to get a total 8 ohm load. Similarly, 2 x 4 ohms would have to be in series to give an 8 ohm load.
     
  11. johnnyha

    johnnyha Tele-Afflicted

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    D'oh, I just realized that thanks! And from what I have read a series wiring gives a slightly richer tone.
     
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