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Parallel wiring?

Discussion in 'Amps and Cabs [BG]' started by bass_player_cd, May 10, 2002.


  1. bass_player_cd

    bass_player_cd terminated.

    Aug 21, 2000
    OK
    I need to hook up a 8 ohm cab to a 4 ohm cab a certain way because my head is 4 impendance. Someone was saying something about wiring them parallel? or some other way. I'm trying to squeeze around music store prices, if I can do it myself.
     
  2. lo-end

    lo-end

    Jun 15, 2001
    PA
    You would get more responses in amps. Read the sticky first.
     
  3. You would so i shall move it. ;)

    first warning...... hmm

    I do know how to wire them in parallel but as such cannot remember off the top of my head. If there is no response to this in say 2 days IM me please ;)

    :D:D

    Merls
     
  4. Johnny BoomBoom

    Johnny BoomBoom Supporting Member

    Jun 8, 2001
    Glasgow, Scotland

    If you hook up the 8 ohm and the 4 ohm cab you have there you will present an impedance of 2.67 ohms. This is below what your 4 ohm head can handle and you could damage your head!

    You will need to get change the 4 ohm cab for an 8 ohm cab if you want to hookm up 2 cabs to your 4 ohm head.
     
  5. Unless I'm missing your point, it can't be done.

    Parralel connecting an 8 and a 4 gives 2.66 Ohms. As your head's designed to run into 4 Ohms, your 2.66 will present too high a load with whatever consiquences that brings!!

    The two cabs will, naturally, share the output from the head unequally: that might or might not be a problem depending on the cabs.

    On the face of it your best (only?) solution is to completely rethink your speaker situation. If you want 2 cabs then it has to be 2 off, 8 Ohm in parallel = 4 Ohms.

    John


    PS
    Johnny

    Looks like you got there first, mate.

    John
     
  6. He's talking about wiring them in series.Their was a good article on doing this in Bass Player magazine a few years ago.Go to their website and do a search.You have to make a cord with three phone plugs on it to make it work.Be aware if you do make this cord and run your cabs in series your amp will put out less power because the impedance will go higher.
     
  7. steve-o

    steve-o Guest

    Apr 17, 2002
    i couldn't find the article.
    could you tell me more?

    steve
     
  8. Series wiring will up the impedance to 12 Ohms. It's physically more difficult to series wire. You'll either have to break into the cabs and alter the wiring (not recommended unless you know exactly what you're doing) or have built / buy a kind-of patch box to do the job.

    As Blue Bass 2 says, you'll develop a fair bit less power across 12 Ohms so it's got to be questionable as to whether it's worth the effort.

    John
     
  9. Series wiring is a lot easier to do with 5-way binding posts and banana plugs. It should look something like this -

    Wire #1: Amp (+) to cabinet 1 (+)

    Wire #2: Amp (-) to cabinet 2 (-)

    Wire #3: cabinet 1 (-) to cabinet 2 (+)

    This should present 12 ohms to the amp - you'll lose power but it'll work without cooking your amp :D
     
  10. steve-o

    steve-o Guest

    Apr 17, 2002
    that really isn't worth it
     
  11. Depends on how much power his amp puts out. I have a power amp that'll dump 1000w into an 8 ohm load - at 12 ohms it'd still be good for 750w give or take.
     
  12. I agree. But I was presuming he wanted to drive into 4 Ohms with his head rated @ ??? Watts into 4 Ohms. Err, a bit clumsy, that, but you get my drift:D

    John
     
  13. Yup - but his head's not 2 ohm stable and he has one 8 ohm and one 4 ohm cab.
     
  14. So if his head is max rated out into 4 Ohms, then into 12 Ohms the power would be fairly well down, that was all. Therefore under those circumstances there seems point in series connecting his cabs and using them with that head.

    Just wondered whether he'd be better off using either the 8 or 4 on it's own, power handing considered, of course.

    John
     
  15. He might very well be better off using a single cab :)
     
  16. Nino Valenti

    Nino Valenti Commercial User

    Feb 2, 2001
    Staten Island NYC
    Builder: Valenti Basses
    Here is the article from bass player. It's from "Bass Player presents: BASS GEAR". It's the issue w/the NS electric bass w/flamed top & EMG & peizo p/u.


    The File is too big to be put here. If ou wanty ity, I'll email it to you. I'm gonna try tyo make is smaller. BRB
     
  17. I have a 4 ohm head and am running a 4 ohm cab in parrallel with a 8 ohm cab. sure it gives u 2.67 ohms but thats a DC resistance as measured by a multimeter. I run this setup for hours on end and sure it gets warmer than usual but hey it hasn't died. I guess though, it is a homebuilt amp and if i was a little worried i would just adjust the bias a little lower (just couldn't be bothered right now) ;)

    :D:D

    Merls
     
  18. steve-o

    steve-o Guest

    Apr 17, 2002
    how can you adjust the bias?
    i don't have a tube amp. yet
     
  19. Johnny BoomBoom

    Johnny BoomBoom Supporting Member

    Jun 8, 2001
    Glasgow, Scotland

    So far your amp has been fine - but for how much longer??? Remember that the candle that burns twice as brightly burns half as long! As it's home built, I guess you'll be a little less concerned. I know I wouldn't do that with my Trace head - no danger!!!

    BTW - is this a DC resistance as measured by a multimeter???? I thought it was the application of Ohms Law in a paralle circuit! If that's what it is, why do the amp/cab manufacturers bother. Surely they can't all be wrong to tell you 'this head is 4 ohms'.....'use a 4 ohm cab or 2 8 ohm cabs in parallel' Is that a case of what they're telling you is wrong???? Do you know better than all the amp manufacturers???

    Merls - I'm not flamin' you, just a curios public (me at least) needs to know!!!:)
     
  20. Might be running down the wrong street here, Merls, but altering the DC bias of the output stage isn't going to prevent too high a load from wrecking the amp. You either get cross over distortion or you run too much current throught the output devices.

    By running @2.67 you're in grave danger of running the output stage(s) outside the devices' safe operating area. Sure, you can often get away with it. Sometimes for long periods. But you'll be doing the gig of a liftime and it'll pack up:mad:

    I go with Johnny. We're talking Ohms law, not measurement with a meter. There's no doubt that the impedance of a speaker is very dynamic: not my field of knowledge, though. I suspect that the impedance will fall (well?) below 2.67 under some conditions and that's when the trouble really begins.

    Again like Johnny, not flamin', just offering suggestions, and all IMHO, of course.

    John