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Minimun Impedance

Discussion in 'Amps and Cabs [BG]' started by RedGrange, Mar 8, 2003.


  1. RedGrange

    RedGrange

    Jun 11, 2000
    Springfield, IL
    one of my bass heads says it has a minimun impedance of 4 ohms...

    this is probably a stupid question... but can I run just one 8 ohm cabinet with it? There is nothing about it in the owner's manual.
     
  2. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    More than (>=) 4 Ohm is fine (e.g. 8 Ohm), less is not.
     
  3. bentem

    bentem

    Oct 18, 2002
    Rockville, MD
    Its not a stupid question, i have asked tons of impadencce questions becore. You can run a 8ohm cab, but it wont be as loud. If you have two 8ohm cabs, on the other hand, they add up to 4ohms, and you will get the full power from the amp.

    Im surprised its not in the owners manual.
     
  4. Killdar

    Killdar

    Dec 16, 2002
    Portland Maine
    you can run any impedance with a head that is 2 ohms....but if you try to plug a 4 ohm minimum head into a 2 ohm cab, you will blow the amp. or so I hear.
     
  5. outofstep

    outofstep

    Dec 5, 2001
    Sonoma, CA
    sooo. are you saying my 300w head (4ohms) plugged into a 8 ohm cab will be how loud? what would the similar power of the amp be if say the head were an 8 ohm head?

    i have a 300w head at 4 ohms and can pick up an 8 ohm cab for pretty cheap...
     
  6. If it's a solid state head...yes.
    If it's a tube head...no.
     
  7. If you plug a 8 ohm cab to your 300 watt head, it will be producing around 150 watts of power, since your heads minimum load 4 ohms.

    If your 300 watt head was designed for a minimum load of 8 ohms (which is not usual, i think) and you plugged it a8 ohm cab to it, it will be delivering the total amount of 300 watts through the cab.
     
  8. outofstep

    outofstep

    Dec 5, 2001
    Sonoma, CA
    can you make an 8ohm cab into a 4 ohm cab?
     
  9. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    It will be more than 150 watts. It's will be a bit over 200. But that's all relative because it won't actually sound much quieter. You'll lose some headroom but the difference in volume between 210 Watts and 300watts is actually quite small. Bear in mind that to double your volume, you need to multiply your watts by 10. Usually the drop in volume when going from 4 ohms up to 8 has more to do with dissconnecting a speaker cabinet and having less speakers pushing air.


    Technically, you can but it's not normally worth it. If it's only got one speaker, you'de have to get it reconed and ask them to make it 4 ohms. Or you could add some resistors but they'll eat up just as many watts as you'd salvage. If it's got more than one speaker, you may be able to re-wire the speakers to change the impedance but you chances of ending up with a 4 ohms load are slight. What sort of cab is it?
     
  10. outofstep

    outofstep

    Dec 5, 2001
    Sonoma, CA
    is ~200w into a 410 cab enough power with a marshall 100w, PA and drums to compete with?
     
  11. outofstep

    outofstep

    Dec 5, 2001
    Sonoma, CA
    nate, i have the same fender bxr300 amp... i guess i need to get another cab to bring it down to 4ohms so that there is more bass sound. ??
     
  12. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    a 100w marshall guitar amp canm overpower most PA's. Guitars don't need the same number of watts as basses bacause the frequencies they're dealing with arent as watt-hungry as low frequencies. As a general rule, the bass player needs at least 4 times the power of the guitarist to be heard clearly. Of course it depends how loud your guitarist plays.
     
  13. Nate Dawg

    Nate Dawg

    Apr 8, 2000
    Denver, CO
    I'd get another cab. I used a Peavey 410 with it for about a year, but I was always clipping it. Then I added an 8 ohm Avatar 115 and it made all the difference. So much louder and no clipping problems.

    I'd recommend against using the low frequency boost on that amp. It sucks up a ton of power in exchange for a sub-par 80 Hz boost. Adding a decent 8 ohm 15 to the 410 will give you all the low frequency sound you need while still giving leaving extra power.
     
  14. outofstep

    outofstep

    Dec 5, 2001
    Sonoma, CA
    i'm looking at a 2x10 and a 1x15 set of cabs... think that'd work out well? i'm looking for portability, but with enough power that i dont have to worry too much...

    oh and the bxr300 amp i have is a pulled amp outta the combo and its racked..
     
  15. Nate Dawg

    Nate Dawg

    Apr 8, 2000
    Denver, CO
    Sounds good to me. That's a pretty common setup.