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another impiedance question.

Discussion in 'Amps and Cabs [BG]' started by sloppysubs, Jan 14, 2004.


  1. sloppysubs

    sloppysubs

    Nov 24, 2002
    Swansboro, NC
    can you run two 4 ohm cabs off of one 8 ohm amp? doesnt that allow you to get the maxx power use? thanks.
     
  2. PunkerTrav

    PunkerTrav

    Jul 18, 2001
    Canada & USA
    Nope. Runnign two 4 Ohm cabs will give you a total resistance of 2 ohms. That is dangerously low for an 8 Ohmp.

    Travis
     
  3. sloppysubs

    sloppysubs

    Nov 24, 2002
    Swansboro, NC
    well heres my dilemma then. i want to run a 2x12 and 2x10 off one amp. what should the impidedence of each part be? whats the safest way?
     
  4. warpedmephisto

    warpedmephisto

    Sep 20, 2003
    I might be mistaken but if you daisy chained the two 4Ohm cabs, you would get a total resistance of 8Ohms, making it suitable for your 8Ohm head. Someone please correct me if I'm wrong.
     
  5. Blueszilla

    Blueszilla Bassist ordinaire

    Apr 2, 2003
    The Duke City
    'tis true. Running the two cabs in parallel gives you 2 ohms and in series gives you 8.
     
  6. ChenNuts44

    ChenNuts44

    Nov 18, 2001
    Davenport, IA
    Unlike the previous post, NOT true. Daisy chaining is equivalent to parallel. If you daisy chain, you'll still have a total impedance of 2 Ohms. What you can do is make yourself a special cable to wire the two cabs in series. You would then have a total impedance of 8 Ohms.

    Since there are 2 drivers in each 4 Ohm cab, the drivers are very likely 8 Ohm drivers wired in parallel. If you rewired them in series, then connected the two cabs in parallel, you would again have a total impedance of 8 Ohms.

    I would recommend the "special" cable to wire the two cabs together in series, as it's a much more simple solution.
     
  7. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Hi zongeek, here's the skinny:

    "Most" cabs that have two jacks on them, have the jacks wired in parallel. So if you plug one cab into the other cab, and then either cab into your amp, your two cabs will end up "in parallel". In that case, two 4-ohm cabs in parallel will result in a 2 ohm total, which is too low for most amps.

    What ChenNuts44 is referring to, is a different way of hooking up your cabs. Basically what you want to end up with is your two 4-ohm cabs wired in "series", which will give you 8 ohms total. When you hook them up this way, the power will be evenly distributed across the two cabs, and your amp will be perfectly happy.

    To do this, you need to wire up a special speaker cable (or, build yourself a little breakout box with the special wiring inside it). Basically what you want is, the "hot" wire from your amp goes to the center pin of one cab, then the outer pin of that cab goes to the center pin of the next cab, and the outer pin of the last cab goes back to the outer pin of the amp (the "cold" side). When you do this, it's important to observe the polarities.

    This is kind of a screwy way of cabling up a set of speaker cabs (although it works), 'cause the arrangement of the speaker wires is going to be inconvenient. IMO, a better way to do it would be to build a little breakout box with three jacks on it, one for each cab and one for the amp. Then you wire the inside of the box like I just said, so the speakers end up "in series". The advantage of doing this is that you can use standard off the shelf speaker cables and you don't have to do any rewiring or modification.
     
  8. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    No but you can run two 8 ohm cabs off one 4 ohm amp.

    Are you sure the amp is 8 ohms? 4 ohm amps are more common and so are 8 ohm cabs.
     
  9. Johnny BoomBoom

    Johnny BoomBoom Supporting Member

    Jun 8, 2001
    Glasgow, Scotland
    Would this be from the Peavey Mark III head in your profile????

    Isn't Peavey one of the companies that the amps can outpout inot 8, 4 or 2 Ohm (depending on particular model).

    Might be worth checking your user's manula or the Peavey website to double check what power your amp outputs into what load. Then you can see if two 4 Ohm cabs will work for you!
     
  10. sloppysubs

    sloppysubs

    Nov 24, 2002
    Swansboro, NC
    hey yea it is the peavey head in my profile. but its a peavey mark 3 but not the regular mark three. it was the "cooler" one that has the blue/green on the front of it. but i bought it used and it doesnt say whether or i not i can run at different impiedence rates.

    so i could run 2 8 ohm cabs from one 4 ohm amp? i might do that then.

    thanks for all that good info on daisy chaining and parrelleling, however, to be honest its very confusing. im more of a plug and play kind of guy. so if the 2 8ohms with a 4ohm amp works, sign me up. thanks guys.
     
  11. Johnny BoomBoom

    Johnny BoomBoom Supporting Member

    Jun 8, 2001
    Glasgow, Scotland

    Check here and see if you can find the user's manual online!


    http://www.peavey.com/support/searchmanuals/results.cfm



    PAge 4 of the manual says minimum impedance 4 Ohms....so running two 8 Ohm cabs is OK!
     
  12. sloppysubs

    sloppysubs

    Nov 24, 2002
    Swansboro, NC
    well if i can run a 4 ohm amp with 2 8 ohm cabs...im set. thanks for all your help guys.


    now what cabs do i get...new thread.
     
  13. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    I thought you may have typed it back to front :)
     
  14. sloppysubs

    sloppysubs

    Nov 24, 2002
    Swansboro, NC
    ok i was talking to a friend of mine and he says that if i run 1 4ohm head into 2 8ohm cabs...thats bad. he says it should be 1 8ohm head into 2 4phm cabs. he says its like math. 8/4=2. so 2 4ohms for every 8 is what hes saying. im so confused.
     
  15. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    He's wrong. Tell him to go do some research.

    The formula for calculating impedance of parallel cabs is:-

    Resistance = 1 / (1 / R1 + 1 / R2 )

    so for 2x 8 ohm cabs = 1 / (1/8) + (1/8) = 4.

    for 2x 4 ohm cabs = 1 / (1/4) + (1/4) = 2.

    for one 8 ohm and one 4 ohm = 1 / (1/8)+(1/4)=2.667

    When speakers are hooked up in series, just add together the resistance values:-

    so 8+8 = 16 ohms.
     
  16. sloppysubs

    sloppysubs

    Nov 24, 2002
    Swansboro, NC
    so point being i can run 2 8ohm cabs from 1 4ohm amp? if so, then im finished here. im not hooking them in a series. i have 2 spaeker outputs on my amp, so im gonna run one of those to the 2x12 and one to the 2x10. and im hoping this can be done. man thsi is worse than the SAT.
     
  17. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    You got it.

    4 ohm amp ------> 8 ohm cab------> 8 ohm cab.

    the 4 ohm amp gets a 4 ohm load. Perfect.


    This will also work

    4 ohm amp ---- 8 Ohm cab
    \---- 8 ohm cab.

    Enjoy.
     
  18. sloppysubs

    sloppysubs

    Nov 24, 2002
    Swansboro, NC
    alright ill give it a shot then. thanks.