Dismiss Notice

Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

Driving two 4 ohm cabs with a 4ohm min. load head.

Discussion in 'Amps and Cabs [BG]' started by Selta, Sep 21, 2003.


  1. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    Someone out there has gotta know how to do this, I know it can be done, I'm just uncertain on how to do it. Links/replies appreciated!

    _RaY_

    (Wanted setup: Sunn 2x15 (4 ohm) + PV 4x12 (4 ohm) drivin by my Acoustic B320, 4 ohm min load)
     
  2. Running 2 ohms is pretty harsh for an amp.
     
  3. "I know it can be done..."

    Sorry to burst your bubble, but you basically have two choices:

    1) run the two cabs in parallel. End result: a 2 ohm load to amp, therefore a fried amp. No good.

    2) Run the two cabs in series. Net result: a 8 ohm load to the amp. The amp will put out half its rated power, but will do so happily forever...You'll need to do special wiring.

    Well, ok you have more choices:

    3) Pick the best sounding cab and just use it. 4 ohms, amp is happy, full power.

    4) Buy a couple of 8 ohm cabs.

    5) Buy a new head.

    Your solution is option #3. Live with it. (And go take an electronics class to learn Ohm's law.) :bassist:
     
  4. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    I know all about ohms, trust me, I've done enough wiring, but I really don't feel like making both cabs 8ohm, its so much...like work. Looks like that's what I'll do though.
     
  5. And exactly HOW do you propose to make your cabs 8 ohms?


    Why don't you so a Search on this forum? Your same question gets posted at least twice a day. And we always post the same answers over and over.

    If you know so much, just go do it.


    P.S. I will answer my rhetorical question. You can't make a 4 ohm cab into an 8 ohm cab by "rewiring it". You can make it into a 16 ohm cabinet, but not an 8.
     
  6. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    Why not an 8? 4 ohm + 4ohm = 2 OR 8 ohm, depending on the wiring. Explain your point of view, I'm just not seeing it. And plus, both 16 ohm, being a total load of 8ohm, wouldn't be so bad though 78 in^2 of air being moved, like 280W @ 8 Ohm here...(going off a meter I have here at home anyway)
     
  7. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    And actually I DID do a search, just never found answers to all my questions. There has got to be a way to reach 4 ohm between 2 4 ohm cabs, I KNOW for certain I saw it somewhere before, someone explained it once.

    _RaY_
     
  8. Nope. Short of reconing all the speakers to be 8 Ohms there's no way to connect two 4 Ohm cabs to total 4 Ohms. ;)

    If you saw it somewhere, it was wrong. Sorry.
     
  9. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    Well mark, I guess it's a good thing that's not what I'm attempting to do. I want the total laod that the amp sees to be 4 ohm. Which means making each cab 8 ohm. Can't you wire 4 4 ohm speakers to 8 ohm?

    _RaY_
     
  10. I implictly meant internal wiring....;)
    There isn't any way to do it short of changing the impedances of the drivers or changing Ohm's law.

    With a 4 Ohm 412, you can rewire it to be 1 Ohm (all parallel) or 16 Ohms (all series). The only other combinations (two series pairs in parallel or two paralell pairs in series) result in 4 ohms.
    With the 215, you can do 16 or 4.
     
  11. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    OK one cab at a time. Lets start with the 2x15. It currently running a 4 ohm load, which means it has one of 2 things going on inside. It could have 2 x 8 ohm drivers wired in Parallel (likely), or it's may even have 2 x 2 ohm speakers wired in series (very unlikely). Assuming it's 2x8 ohm speakers, the ONLY other way to wire it is in series, the end result being 16 ohms. The only way to get 8 ohms out of this cab it to dissconnect one of the speakers...........

    Now to the 4x10. This will almost certainly have 4 x 4 ohm speakers wired in a combination of series and parallel to get the 4 ohms final nominal impedance. With more speakers to play with, there are more wiring options available. None of em come to 8 ohms with all speakers connected.

    Sorry, that's the laws of physics at work, and they don't change for anybody.
     
  12. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    Well, the 2x15 right now has 2x8ohm in it, having the original Sunn speakers in it, BUT my teacher gave to me with it a set of 2 ohm JBLs. (at least, that's what he told me they were, I'm gonna meter them just to be sure).

    The 4x12 has 4 4 ohm speakers in it. I think. I gotta get 4 new ones for it here anyway, what should I buy to bring the cab to be 8 ohm total?

    I'm gonna re-meter everything, I never did trust those tags ever since I played on one marker 4 ohm and it turned out to be 16.

    More replies wanted.

    _RaY_
     
  13. uglybassplayer

    uglybassplayer

    Aug 24, 2001
    New Jersey
    Nope! The closest you can get is mismatched :meh:: 6 ohm (2 spkrs parallel = 2 ohms connected parallel to the other 2 spkrs which are connected to each other in series,) or 10 ohms (2 spkrs parallel = 2 ohms connected series to the other 2 spkrs which are connected to each other in series)

    - Frank.
     
  14. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    Well, I can do 6 ohm, as long as I don't end up pushing my amp below 4 total I don't care what the cabs are....fgenus, if you can IM me on AIM (bassr305) or PM me, hehe.

    _RaY_
     
  15. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    6 ohms is only for the one cab so it only solves part of your problem. Not only that, the 4 speakers won't recieve an even distribution of watts so some will be softer than others..

    Seriously, if you're happy to spend money on 4 new 12" speakers, it would be money better spent on a amp that can run at 2 ohms - that way you won't have to modify the cabs at all.
     
  16. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    It's not that I'm willing to spend it to get a different ohm off the cab, it's just a fact that I need four new ones. One's GONE and three others are on their way.

    _RaY_

    And plus, I will NEVER ditch my Acoustic head!
     
  17. Rockbobmel

    Rockbobmel Supporting Member

    I hooked up my Mesa to 1)4ohm cab, and 2) 2-8OHM cabs for a total of 2 ohms. The cabs were 1-(1-15+4-10),2-a(1-18)and a(4-10). The sound was very sperad out and I did not like it. I went back to either cab config and it was much better focused and just as loud. I think you will not gain anything with what you got. Get another amp, or run one cab. The 4-12 is shot anyway.You could get a used PV mono block ext amp. That would make your setup big or real big so you can Korn out.
     
  18. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    I'm taking offense to that comment. But, I'm not going to turn this into a ranting thread, I'll just let your immature prejudice (sp?) remark alone.

    Anyway, I'm in the process of getting 3 8ohm drivers for my 4x12, and found out my Sunn drivers are 8ohm, whereas the JBLs are 4. So, problem solved, thanks everyone for the input, with a few exceptions...

    _RaY_
     
  19. Rockbobmel

    Rockbobmel Supporting Member

    Sorry I was insensitive...I'll never reply to your posts again...