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8ohm vs 4ohm cabs

Discussion in 'Amps and Cabs [BG]' started by benchbass, Mar 25, 2013.


  1. benchbass

    benchbass

    Mar 17, 2010
    Calgary Alberta
    Hello, when looking at amps, they often say that they have more watts at 4 ohms and less watts at 8 ohms. This makes it seem like 4 ohm cabs are better than 8 ohm cabs. What's the advantage to 8 ohm cabs then?
     
  2. Liv3rman

    Liv3rman

    Dec 28, 2012
    Running 2 8ohm cabs gives you a 4ohm total load on the amp. So 1 4ohm cab will receive full power, as will 2 8ohm cabs between them.
     
  3. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    More watts doesn't get you louder, generally, more cabs does. If you have a 4 ohm cab, you are stuck with one cab, with an 8ohm cab, you can add another.
     
  4. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    1) It's more complicated than that.
    2) Read the sticky threads here in the amps section.
    3) You probably won't even hear much of a difference running one 4 ohm cab vs. one 8 ohm.
    4) The main "advantage" of 8 ohms is that you can hook up TWO cabs (assuming they are wired in parallel..... and most are) and that will get you a 4 ohm load. Most amps are rated at a 4 ohm minimum. If you were to chain together to 4 ohm cabs that would drop you to 2 ohms, below the minimum ohm rating of most cabs. So, in short, the ability to expand your rig to 2 cabs without burning up your rig would be the main advantage of running 8 ohm cabs. You will gain much more volume by running two cabs rather than running one at "more watts" (to use your term) at 4 ohms. Plus you can always take one cab for smaller gigs/practices.
     
  5. Afc70

    Afc70 Supporting Member

    Feb 2, 2004
    Northeast Arkansas
    There are amps that will run comfortably at 2 ohms of course- Ea IAmp 800, etc...
     
  6. Plucky The Bassist

    Plucky The Bassist ZOMG! I'm back from the dead! Supporting Member

    Jul 30, 2010
    Houston, TX
    Mr. Foxen pretty much hit the nail on the head.

    Playing 500w through a 4-ohm 4x10 cab is going to be quieter than playing 500w through two 8-ohm 4x10 cabs. Go for the 8-ohm.
     
  7. jnewmark

    jnewmark Just wanna play the groove. Supporting Member

    Aug 31, 2006
    Stax 1966
    Third St. Cigar Records staff musician.
    There's a couple different scenarios also. If you go the pre/power route, most power amps have two channels, so you could run two 4 ohm cabs. In the case of the single 4 ohm cabs, I think if you are dead set as a one cab kind of guy, the 5 lb, 500 watt heads, like the MB F500 would be great, giving you 500 watts at 4 ohms ( assuming the cab can take it ). For example, Greenboy's Bassic 115 cab is offered in a 4 ohm version,perfect for a head like the Walkabout.
     
  8. Egbert89

    Egbert89

    Aug 30, 2012
    Holland
    If you just wire two 4Ohm cabs in series then you'd have a total load of 8Ohm... Then if you really really need the power you could add one 8Ohm cab, or two 4Ohm cabs in series :p

    However to get back to the OP, it depends on your amp...
    If the amp can deal with the 2Ohms, then I'd prefer one or two 4Ohm cabs. If that amp would power one 4Ohm cab then it won't deliver its 2Ohm rated amount of watts...
    If I'd hookup the two 4Ohm cabs in parallel the total impedance would be 2Ohms, so the amp can deliver it's rated capacity :)
    But that's just my 2cents
     
  9. benchbass

    benchbass

    Mar 17, 2010
    Calgary Alberta
    So what I'm getting from this is to aim for a cab that is twice the capacity of the head?
     
  10. AtomicPunk

    AtomicPunk Supporting Member

    Dec 3, 2007
    Detroit Metro, MI USA
    Just get a Shuttlemax 12, run a 4 ohm load on each side, problem solved. :) Oh, and stand back.
     
  11. The power handling of the cab limits the loudness. Peak power from a decent amp is double its rated power so it's usually easy enough to stretch the 8ohm cab to its limits. Adding another 8ohm cab brings the goods.
     
  12. A-train

    A-train

    Nov 22, 2005
    San Antonio,Tx
    Most of the guys responding on here are completely right. Get an 8ohm cab and add another later. More watts won't necessarily give you more volume but more speakers will. Simple physics, more speakers push more air so 500w through 4 speakers won't sound as loud as 500w through 8 speakers.
     
  13. Egbert89

    Egbert89

    Aug 30, 2012
    Holland
    All this talk about 500W through 4 or 8 speakers...
    I run 200W (SS) through 2x10" and never had to put the volume past 20% xD
    But that's a whole different story haha
     
  14. tbirdsp

    tbirdsp

    Sep 18, 2012
    Omaha, NE
    You aren't understanding this. The ohm rating of either a cab or head is not the "capacity". It's a measure of the resistance (impedance actually) of the speakers in the cab, and the rating of the amplifier is the minimum load the amp can take.

    The best way to understand this IMHO is to think of the amp as a water pump and the speaker cab as a pipe with a narrow restriction in it. Now if there's a fair amount of restriction to flow (8 ohm cab) the pump (amp) will happily pump away, but it could move more water (send more power to the speakers) if there was less of a restriction. If the pipe restriction (say you add another pipe to the system with the same restriction of the first one - but now you have two paths for the water to flow so the restriction is reduced by half - just like adding another 8 ohm cab) was just big enough that the pump could pump it's maximum amount of water (4 ohm load for an amp rated at 4 ohm minimum) then that's he best case - max water flow (power to speakers) but no damage to the pump (amp). However - if the pipe was wide open (say you added yet ANOTHER pipe - or 8 ohm cab to the system) and could take more water than the pump (amp) could pump (like adding more cabs to reduce the load below the 4 ohm minimum) - then bad things happen - the pump (amp) "pukes its guts out" trying to flow more than it should.
     
  15. To carry the pump pipe analogy along... a skinnier 8ohm pipe is carrying enough water to fill the bucket brigade's buckets so making the pipe fatter doesn't accomplish anything but wet feet, but if you added a second line of members and buckets to the brigade you could put more water on the fire. ( but perceived audio volume is not linear like volume of water )
     
  16. benchbass

    benchbass

    Mar 17, 2010
    Calgary Alberta
    I see! So if I was dead set on only 1 cab, I'd get the 4 ohm (larger pipe) to get theBut if I got the 8 ohm ( smaller pipe ) I could add a second line without damaging the
     
  17. benchbass

    benchbass

    Mar 17, 2010
    Calgary Alberta
    Amp
     
  18. No, the 4 ohm one is no louder than the 8ohm. Only when you have a very underpowered solidstate amp is there any advantage to wringing watts out of that amp with a lower impedance cab.
     
  19. Depends if your amp head can handle a 2 ohm load,many do. Then you can run 2- 4 ohm cabs.
     
  20. A-train

    A-train

    Nov 22, 2005
    San Antonio,Tx
    You have it right now Benchbass. If your set on just 1 cab get the 4 ohm but if you think you may get a 2nd cab later than get the 8 ohm one.
     

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