4 ohm amp with an 8 ohm speaker?

Discussion in 'Amps and Cabs' started by wishkahdaddy, Aug 17, 2011.

  1. wishkahdaddy

    wishkahdaddy Silver Supporting Member

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    Just curious who has experience with running a 4 ohm amp with an 8 ohm speaker? I've been reading in a few different forums where this was a common practice for Mr. Dumble. Just curious what others have experienced-good or bad.
    Thanks
     
  2. Steve Hotra

    Steve Hotra Silver Supporting Member

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    Good question! I would like to know that as well.
     
  3. chillerthanmost

    chillerthanmost Member

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    slightly earlier break up with a small volume drop
     
  4. gillman royce

    gillman royce Supporting Member

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    It's safe to do as long as the ohmage is above the specific designation. In other words, 4,8 & 16 are ok; 2 ohm - no no
     
  5. GCDEF

    GCDEF Supporting Member

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    Not necessarily. Some amps tolerate a mismatch, others don't. Read the manual to see if it's safe.
     
  6. Bluzeboy

    Bluzeboy Member

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    Yep... even if they tolerate the mis-match.. probably no more than 1 each way.. i.e. 4 ohm into either 2 or 8 ... assuming this is a tube amp.
     
  7. plexistack

    plexistack Member

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    My amp tech says it's a no-no, but it keeps him in business.
    If you really want to pay for a new OT, go for it.
     
  8. riffmeister

    riffmeister Gold Supporting Member

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    I know of at least one world class touring pro that does it........Fender amp with a 4 Ohm tranny into an 8 Ohm speaker.

    Personally, I have done mis-matches in both directions (e.g., 8 Ohm tranny into a 4 or 16 Ohm load) without incident. But it's a good idea to keep everything matched if possible.
     
  9. crzyfngers

    crzyfngers Member

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    i've run a 4ohm speaker in my 8ohm amp.(boogie mk1). i like the sound of that.
     
  10. JubileeMan 2555

    JubileeMan 2555 Member

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    Been doing just that in my homebuilt vibroverb for over a couple of years. 4ohm bassman tranny into a 8ohm JBL.

    People like to freak out about missmatching, but its not an exact science. Speakers don't produce a constant 8ohms of resistance, and from what I can tell, different tube manufacturers even claim different required reflected loads. This is why most say one missmatch isn't a problem...because ITS NOT.
     
  11. leodiditright

    leodiditright Supporting Member

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    Is your guitar tech paranoiac?

     
  12. leodiditright

    leodiditright Supporting Member

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    Yep! doin' it all the time with my '72 Bandmaster Reverb into an 8ohm cab.

     
  13. Bluzeboy

    Bluzeboy Member

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    Wait a minute.. I thought the 72 Bandmaster was 8 ohm.
     
  14. leodiditright

    leodiditright Supporting Member

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    It could... but I think it's 4 ohm. Maybe a real authority vintage amp specialist will chime in...

     
  15. crzyfngers

    crzyfngers Member

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    not a specialist but i had a blonde one. it was 8ohm.
     
  16. leodiditright

    leodiditright Supporting Member

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    How did you find out? because on the back panel of my silverface, there is no indication.

     
  17. crzyfngers

    crzyfngers Member

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    amp tech.
     
  18. Bluzeboy

    Bluzeboy Member

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    As I remember (which could very well be faulty). The 61 was 8 ohm 62 - 64 was 4 ohm (like the Bassman) then back to 8 ohm for the Silverface guys.. but.. that's just what I THINK I remember :)
     
  19. Jimsz

    Jimsz Member

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    When I purchased my Mack amp, I asked Don about speaker impedance mismatch as the amp had two 8ohm outputs. He replied:

    "So, you can plug each speaker into its own jack. Or, you can use any configuration you like into one jack: both in parallel for 4 ohms or both in series for 16 ohms. You CANNOT harm the amp regardless of what impedance you plug into one or both jacks. Allow me to explain.

    The jacks in our amps are wired to the 8 ohm tap on the output transformer. However because of the relatively low power output of our amps (under 50 watts) and the high quality of the output transformers (Hammond) and the tubes (JJ), they are perfectly happy to have any impedance speaker cabinet plugged in. At the voltages and power levels that we run, the output tubes and the output transformer never come close to being damaged.

    Because we get this question so often, we actually tested all or our amps by applying an input signal to the front of the amp (at a level higher than any guitar pickup could produce), turned the volume to '10' and left the amp running for over an hour... with nothing plugged into the speaker jack and then with a dead short across the speaker jack! Theses tests simulated the absolute worst case scenarios.

    We took measurements throughout the test periods and confirmed that at no time did the output tubes or output transformers see voltages and currents anywhere near their maximum limits - they were just fine. So, if you ordered any of our amps, you would get two jacks that can each be hooked up to any cab or speaker impedance. "​
     
  20. Bluzeboy

    Bluzeboy Member

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    You know.. now that I think about it for a second.. maybe it was the speakers that were 8 ohm.. but really.. I don't remember.. Someone will chime in I'm sure.
     

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