is it safe to run 8 ohm into 16 ohm?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by gbisn1960, Dec 24, 2003.


  1. gbisn1960

    gbisn1960 Member

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    hey all.. i have a 16 ohm germino cab and a hot cat that i can only select 4 or 8 ohm output on.. is it safe to run the 8 ohm selection into the 16 ohm cab? will it just be less efficient?
    thanks
    Jon
     
  2. VaughnC

    VaughnC Supporting Member

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    Due to flyback voltage effects, it is much riskier running your tube amp into a higher impedence load that it wants to see than lower. However, with most amps, usually a one step mismatch won't cause any problems.
     
  3. John Phillips

    John Phillips Member

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    It will be less efficient, and you may lose some low-end too.

    There are two potential solutions - if the cab is a 2- or 4-speaker one, rewire it for 4 ohms; or get a 16-ohm dummy load and run it in parallel with the cab (with the amp set to 8 of course). Yes, this will throw away half the power, but that's not a lot worse than the power loss caused by the mismatch (which will typically be about 1/3), should preserve the tone better, and may be slightly safer for the amp.
     
  4. gbisn1960

    gbisn1960 Member

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    hmm.. ill try that out.. i dont know much on the whole ohm thing.. but i do know that there are two 16 ohm speakers in the cab (germino) and if there is any way to rewire it for 8 ohm that would be cool.. i did try it today with the cat set on 8 ohms and it turned out well.. sounds like the open back 2x12 combo does, but smooths out the top a little more, and adds a little more thump... thought about trading the hot cat for a dc30, but im not quite sure now.. cant make up my mind
    Jon
     
  5. psychodave

    psychodave Senior Member

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    I run all of my Marshalls at 8ohms into a 16 ohm cabinet(s). I like the tone a lot better.:dude
     
  6. BWilliamson

    BWilliamson Guest

    That's risky, older Fenders seem to handle mismatches without hickuping. Although I've always heard that Marshalls are much more finicky to the impedance and don't like mismatches one way or the other. Never blown one myself but have never run intentionly a mis-match on a Marshall for any length of time.

    Now I have a buddy that has been running a Twin Reverb @ 16ohms for years without problems. He wouldn't change a thing.

    As for the original question, really depends on the OT. If it's overated enough to do it, but then again I can name a couple of techs who could care less what the amp wants to see as to what gives them the tone and say that there is NO problem doing so. Again IMHO it depends on the OT rating but I'm a wussie.

    bwilliamson
     
  7. gbisn1960

    gbisn1960 Member

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    with OT i would assume you are talking about the output tranny... in this case the OT on the hot cat is friggin huge for 30 watts... i would imagine its more than overpowered... but anyways.. maybe its just my imagination :)
    thanks
    Jon
     
  8. BWilliamson

    BWilliamson Guest

    Matchless has a 16ohm tap, on the 15 watters it wasn't connected. Don't know why, well I think I know why as they OT was running a 4k ohm load instead of the standard 8K for a pair of EL84's. They might have had some problems running it into a 16ohm load.

    Anyway the C-30 chassis had a 16 ohm tap according to the schematics and I'm not sure why the Bad Cats wouldn't as well. From the pictures that I've looked at the Badcats switched to vertical mounted trannies compared to the x-mounts in the Matchless series but I don't know if he changed tranny suppliers. You might have a 16ohm tap that isn't hooked up, perhaps a call or email to Bad Cat and see what they say?

    bwilliasmon
     
  9. John Phillips

    John Phillips Member

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    If there are two 16-ohm speakers in the cab then it is already an 8-ohm cab!

    Two speakers in parallel have a total impedance half that of the individual speakers (in series it's double, but you won't have that here).
     

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