if not sure 16 or 8 ohm speaker which is safer

Discussion in 'Amps and Cabs' started by neastguy, Sep 8, 2008.

  1. neastguy

    neastguy Supporting Member

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    for the amp? thanks...
     
  2. Dr. Lo

    Dr. Lo Supporting Member

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    16 ohms would be safer. Running an amp through a speaker that has an impedence that is LOWER than what the amp is looking for will damage your output transformer. Using a speaker that has a HIGHER impedance than what the amp is looking will result in reduced output (volume), but not damage to the amp.
     
  3. neastguy

    neastguy Supporting Member

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    thanks.. good to know..
     
  4. RussB

    RussB low rent hobbyist Silver Supporting Member

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    How can you make that comment (or any comment) when you don't know what amp we're taliking about here? I luv the internet :crazy
     
  5. jrigg

    jrigg Gold Supporting Member

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    Absolutely. The output impedence of the amp is the critical bit of info missing here!!!
     
  6. Dr. Lo

    Dr. Lo Supporting Member

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    Because amps typically are looking for a speaker load of either 16, 8, or 4 ohms. Thus, the safest would be a 16 ohm speaker to avoid frying the output transformer.

    I'm assuming, of course, that the speaker chosen has a POWER handling that is equal to or superior to the power rating of the amp. If it's lower, the risk of blowing the speaker would be higher.
     
  7. michael patrick

    michael patrick Supporting Member

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    The safest would be matching the impedance of the speaker to the impedance of the amp.
     
  8. FrankieSixxxgun

    FrankieSixxxgun Member

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    Winner! That's like asking which gas is safer to run in a car, 93 octane, 87 octane, or deisel and that's it. You kinda need the critical information being the type of car for my analogy. Replace the type of car with type of amp and it fits here.
     
  9. hasserl

    hasserl Member

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    For a tube amp that is wrong, an impedance higher than the amp is designed for is more likely to damage the output transformer than an impedance lower than it was designed for, due to high flyback voltage that is amplified in the output transformer to levels high enough to arc thru the insulation on the windings.

    As others noted above, the safest is the correct impedance to match the amp design. But if you're considering a mismatch and which is more likely to cause damage, it is the high impedance that is more dangerous for the amp. A low impedance will only damage the output transformer if the transformer is seriously underrated for the application, which should not be very common. Tubes will only flow x amount of current, there are limits to how much current they can flow. A decent output transformer should be able to handle the max current of the tubes no problem.

    Now with a solid state amp the opposite is true, in that case a higher impedance load is safer. But when we're talking tubes, it's the exact opposite.
     
  10. neastguy

    neastguy Supporting Member

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    ok say I have a Tiny Terror.. and currently the temp speaker cab I'm using does not show the ohm on the speaker 1x12... but its all I have until I get a replacement .. if I have a choice of 8 or 16... what should I choose? or will I fry something..
     
  11. FrankieSixxxgun

    FrankieSixxxgun Member

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    Yeah, lower impedance will cause the power tubes to get overtaxed. If you tax them too hard you'll likely start blowing power tubes, but power tubes are much cheaper, easier to replace, and not as devaluing to the amp as replacing the OT, so typically if you HAVE to run a mismatched impedance you go lower vs. higher on a tube amp. Seriously though, consult the manual for the amp and match the speaker impedance. There's no reason to go shopping for a new speaker and not get one with the correct ohm rating.
     
  12. FrankieSixxxgun

    FrankieSixxxgun Member

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    So you have an unmarked speaker and you're looking for what setting you should set the impedance selector in the back of the amp? Get your VO meter and measure the speaker.
     
  13. neastguy

    neastguy Supporting Member

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    u guys are high tech
     
  14. fizbin

    fizbin Member

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    Find a friend who knows a little about electricity and has a multimeter. Have them measure the resistance of the speaker by placing the test leads on each of the speaker leads. The resistance measured on the meter will generally be about 1 ohm less than the speaker's impedance rating. Round up.

    You should get 4, 8, or 16 ohms.
     
  15. FrankieSixxxgun

    FrankieSixxxgun Member

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    Unhook the speaker first or you'll get a way funny reading :D Ask me how I know.
     
  16. hasserl

    hasserl Member

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    This is not high tech, this is minimum of what you should know to use and care for a tube amp.

    Get yourself one of these:

    http://www.radioshack.com/product/i...-RSK&retainProdsInSession=1&parentPage=family

    Disconnect the leads from the speaker, set the meter to read resistance/ohms, touch the test probes to each terminal on the speaker and read the meter. The DC resistance you read will be less than the rated impedance of the speaker.
     

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