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running a 4 ohm amp into an 8 ohm cab...what does this mean?

Discussion in 'Amps and Cabs [BG]' started by AJ Love, Jun 14, 2004.

  1. AJ Love

    AJ Love

    Oct 8, 2002
    Madison WI USA
    help me out here please:

    I've got a SWR 400-S bass amp that a good friend is graciously letting me borrow, it runs 4 OHMS in bridged mode (no clue what that means)....today I picked up an Epifani 210 that is rated at 8 OHMS in a screamin deal that I couldn't pass up. How will these two work together?

    I understand the ideal set-up is TWO 8 OHM cabs together for a 4OHM amp, right? but how will just the SWR running into the Epi 210 work?

    I've got a couple of gigs and an important recording session coming up and I want to make sure everything is running smoothly

    to complete the equation I am playing a Fender P Bass running into an Aguilar DB-924 preamp before the signal goes into the amp (the preamp is just the smaller effects box sized pre that takes 2 batteries)

    thanks in advance (I did a search on this topic and found alot of info but didn't find anything about this specific situation)
  2. xb100


    Mar 24, 2004
    NH, In
    Well since the cab it self is 8 ohms the amp will only put out about half its power. So if the amp has a minimum impendance of 4 ohms and is rated at 400 watts it will probly produce about 200-250 watts if you hook it up with the 8 ohm cab. Add another 8 ohm cab and you get the full 400 watts from the amp. I hope i explained that right.
  3. Ericman197


    Feb 23, 2004
    Yup. Overloading is only going to be harmful if you're using a tube poweramp. Your solid state poweramp wouldn't have a problem with the 8 ohm cab, but it won't put out as much wattage ( usually just over half ). The only thing you have to worry about now is running out of headroom.
  4. XB is on the money. But if this is for recording...you'd be doing yourself a favor by leaving the rig at home. Take your Fender and the Aguillar preamp straight into the board. IMO you'll only make things more difficult for the man at the board with the SWR and cab. (Unless your TRYING for something specific to those two pieces of gear...& you're using a mic to the board.)
  5. AJ Love

    AJ Love

    Oct 8, 2002
    Madison WI USA
    generally I prefer the sound of going direct too. For this session we are going to have two tracks of bass, one going direct and one of the cabinet mic'ed. thats the Producers preference and we've gotten good results from it in the past. (Going for a full deep big bass sound, its a Reggae band)

    I appreciate the feedback in this thread
  6. RunngDog


    Jan 22, 2003
    Chicago, IL
    Okay, but then don't you have to split that full 400 watts between the 2 cabs -- so you end up again with only 200W per cab?
  7. "Yup. Overloading is only going to be harmful if you're using a tube poweramp. Your solid state poweramp wouldn't have a problem with the 8 ohm cab"

    Actually using an 8 ohm cab on a 4 ohm amp would be "Underloading" and they are correct, underloading is only harmful on a tube amp.
  8. xyllion

    xyllion Commercial User

    Jan 14, 2003
    San Jose, CA, USA
    Owner, Looperlative Audio Products
    2 cabs with 200W available to each would almost always be louder than a single cabinet with 400W available to it. This assumes the same type of cabinet being used both cases.

    I'd also like to point out that 200W of available power will often get you more volume than you would expect. Of course, this assumes reasonably efficient cabs. There are some cabs on the market require and a much larger amount of power to get loud.

    Overall, don't get hung up on specs. They can be deceiving. The best thing to do is to listen to different combinations and see what sounds good to you.