4ohm amp into a 2.667 ohm load. Safe?

Discussion in 'Amps and Cabs [BG]' started by jimmyjames77, Jul 19, 2009.

  1. jimmyjames77

    jimmyjames77 Supporting Member

    Apr 17, 2005
    Just West of Chicago
    Quick question. I did a quick search and couldn't find anything.
    I'm wanting to run my amp at 4ohms, (it doesn't go to 2 ohm ) into my cabs at a 2.667 ohm load. Is this safe? I know most speakers aren't the exact ohm rating they are rated at anyway. So most loads aren't right anyway. I figured some cabs that "say" they are 4 ohm might be close to 2 ohm anyway...
    What do you some peoples with a bit O' Knowledge say?

    Edit: Yes I do know that ratings are there for a reason. I also know/knew that tube amps are a little different in that regard.
  2. allexcosta


    Apr 7, 2004
    For a few minutes, low volume, probably yes. Long periods and your amp will overheat. When the manufacturer says "minimum 4ohm" they actually mean it.
  3. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    I say you'll burn your amp up if it's only rated to go 4 ohms and you try to take it lower. Impedance does fluctuate while you're playing, but cabs also have an impedance when they're not doing anything, so if you take them down to a level the amp can't handle, then you'll either fry it or send it into protection mode shut down, if you're lucky that is. Those minimums are written on that amp for a reason.
  4. Bassamatic

    Bassamatic keepin' the beat since the 60's

    NO! - You will destroy your output stage or output transformer. That is why the amps is rated 4 Ohms. The DC resistance of the speakers may be different than the impedance, but speaker ratings are pretty close when they are running audio through them.
  5. 60bass

    60bass Gold Supporting Member

    Apr 24, 2005
    North Carolina

    First I'd want to know what brand of amp you're talking about. I wouldn't do it PERIOD just because. Manufactures put those load numbers on there for a reason. If it's a newer SS amp it will probably just go into protect mode and shut down till you run the correct load. If it's an older SS amp, I've seen them blow quick with the wrong load. Which in your case you say is not less than 4 ohms.

    You mention 2.667 so I assume you have 1-8 ohm and 1-4 ohm cab and you want to run them both together, correct? Aint gonna happen if your amp only goes down to 4 ohms, and is it worth possibly torching your head?

    You have to get rid of the 4 ohm cab for an 8 ohm cab or get a head that does 2 ohms. If those aren't options and cash was short, here's what I'd do and have done before.

    Hit Craigslist or the paper and look for a decent rack mount stereo poweramp that you can run at 8 or 4 ohms. I've seen them for 200 bucks many times. Lots of DJ's dump amps. If you're lucky you can find one that you can bridge mono and get some high power out of it. Run that as a slave off the line out of your main amp and problem solved.

    Keep Low :bassist:
  6. R Baer

    R Baer Commercial User

    Jun 5, 2008
    President, Baer Amplification
    Typically, this is never a good idea, but it does depend on the amp. I've run a Mesa Walkabout into three 8ohm cabinets on many occasions and never had a problem and there are many threads on this amp running 2ohm loads, so it is well documented. Be very SURE you know what your amp is capable of before trying this!
  7. Don't do it! I fried a GK 400RB output section thinking I had an 8-ohm load when it was actually 2 ohms. You can wire the speakers in series - but your amp will produce less power for a 12-ohm load and may have a lower overall volume despite the extra cone area from the extra cabs.

    You will need to make or buy a connector box - here's some background:


    Good luck.
  8. illidian


    Jul 2, 2004
    While your amp may be able to handle the load, perhaps even for extended lengths of time, without knowing the model I cannot recommend this to anyone else as a safe endeavor. Run at your own risk.
  9. Hi.

    I wonder why there's a FAQ sticky about the subject...

  10. georgestrings

    georgestrings Inactive

    Nov 5, 2005

    Sound advice right there...

    - georgestrings
  11. greenboy


    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Yes. Go right ahead. Since it's YOU, and YOU really want it, and want it bad, ignore all the manufacturers' ratings, and all the stuff in those pesky FAQs, and that stupid scientific nonsense, and just GO RIGHT AHEAD!

  12. What they said. There are particular instances where you can win this, but they are few. For example, I have an 8ohm 4x10, and a 4ohm 2x10. I want to use them together, for 6 10's. But, oops, that would be a 2.6ohm load. So I wired the 2x10 for 16ohms. Win, works great.
  13. Sten


    Nov 18, 2001
    Great solution - every driver gets the same amount of power too! I bet you don't gig much with the 2x10" (16ohm) alone though?
  14. Yes, they do. I installed a DPDT switch in the 2x10 to go between 4 and 16ohms.
  15. UncleBalsamic


    Jul 8, 2007
    Nice title Greenboy ;)
  16. IvanMike

    IvanMike TTRPG enthusiast, Happy, Joyous, & Free. Supporting Member

    Nov 10, 2002
    Middletown CT, USA

    Not even if you really, really, really, want it to be ok.
  17. greenboy


    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Not even with a special dispensation from the Pope?

    : {

    <dreams shattered>
  18. Marley's Ghost

    Marley's Ghost Supporting Member

    Feb 9, 2002
    Tampa, FL
    If you do decide to ignore the sage advice here on why this is a really bad idea, then when you blow your amp you must start a whiny amp blown thread so we can mock you.
  19. Sounds like someone just got their junior magicians book, and is looking to conjure up the magic smoke
  20. silky smoove

    silky smoove Supporting Member

    May 19, 2004
    Seattle, WA
    BAD! ummmmm.... Yeah, that's all I have to say. Bad... :D