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Ohms

Discussion in 'Amps and Cabs [BG]' started by lowtones, Sep 24, 2001.


  1. So if I'm running an amp that delivers 500 watts at 2 ohms, and I'm using a 4 ohm cabinet, I'm getting around 275 - 300 watts, give or take.

    My question is, if I get another 4 ohm cabinet and run them both from the same amp, does that lower the total impedence down to 2 ohms and let me run the full 500 watts?

    Thanks in advance.
     
  2. Correct.

    chris
     
  3. Luis Fabara

    Luis Fabara

    Aug 13, 2000
    Ecuador (South America)
    Audio Pro - Ecuador
    Indeed.
     
  4. Perfect. Thanks guys.
     
  5. Luis Fabara

    Luis Fabara

    Aug 13, 2000
    Ecuador (South America)
    Audio Pro - Ecuador
    It is always a pleasure to help.
    May I ask what Amp and cabs are you planning to use?
     
  6. I have a Randall RBA-500 head running a RB 215S 2x15 4 ohm cabinet.

    I might look into one of those new Carvin RL210T 4 ohm 2x10 w/horn cabs. They look nice
     
  7. Wow, this thread is ancient, but it pertains to directly to a question I've got; so here goes nothing...

    I recently acquired the exact same Randall head (The RBA-500), and though the seller told me it came with a 2x15 cab, it turns out it was really a Randall R212S 2x12 (guitar) cab. The guy said the amp was a friend's of his, and he didn't know much about the technical side of things, but from what I could get him to recall he seemed to remember the previous owner running it quite loud.

    There is next to nothing at all online about these old orange line/red line/red faced Randall Amps; but from reading the back carefully, I've determined that the 2x12 is 4 ohms, and it stands up to the RBA-500 wonderfully. The cab also has a separate 1/4th inch output jack on the back plate as well, and I'm about to get my hands on an old Kustom 2x15 which is rated at 4 ohms.

    I'm wanting to chain the two cabs together to see how it sounds, but I'm worried the guitar cabinet couldn't handle the 2 ohms that the head would be putting out at that point. Does anyone know if this is safe to do? Or should I just forget about it and run the RBA solely with one cab or the other?

    Thanks in advance!
     
  8. RedLeg

    RedLeg Supporting Member

    Jan 24, 2009
    용산 서울 한국
    Nov Shmoz Ka Pop?
    Unless you do not mind frying your amp (remote worst case scenario)
    a multimeter reading might benefit you
     
  9. Hi.

    Welcome to TalkBass sectsmonk.

    A relevant thread resurrection (by searching no less I'd imagine) if there ever was one, I'd say :).

    Since the two cabs have an identical impedance, the power is distributed equally.

    That means the 212 won't recieve any more wattage than it was before.

    You should be safe.

    Whether it will soud good, well, that's an another matter ;).

    I'd use just the 215.

    BTW, is it really a 2 Ohm stable head?

    Regards
    Sam
     
  10. Jim Carr

    Jim Carr Dr. Jim Gold Supporting Member

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic and card-carrying union member Musicians Local 72-147
    The RBA-500 is not on the current 2 ohms faq list compiled by TBer thedude:

    http://www.3ms.com/bass/2ohms.htm

    If it really is 2 ohm capable, please let him know so he can list it.

    Assuming it is in good condition and that by old you mean from the 70's, those cabinets really punch! I doubt the 212 would be needed or have much to add other than standing in the way of the 215.

    If the head is not 2 ohms stable, you could fry it in seconds. :eek:
     
  11. Oobly

    Oobly

    Jun 19, 2008
    I believe the specs list it as 500W peak into 2 Ohms, 300W RMS. Into 4 Ohms it will probably only be pushing around 200W RMS.

    Should be safe to hook up both cabs and try it out.
     
  12. I took a meter to the Kustom's speakers, after prying her open when I got her home, and one speaker read cleanly at 8 ohms while the other wavered between 8,7, and 6 ohms. The magnets on these suckers are *huge*, but I couldn't identify a make, model, or manufacturer for them. I'm not very experienced with wiring, but it looked as if they were wired in series,which I believe makes this cab 4 ohms, correct? I then trawled around for a bit on talkbass to make sure I understood the whole 'daisy-chaining' concept, and had at it.

    With my volume set at 0, and my gain set nearly at 2, I hit an open (low) C on this insane stack, and rattled all the pictures on the walls in their frames. I've never heard anything quite like it. I'm ecstatic.
     
  13. As soon as I've come down of this rather righteous gear buzz and managed to get some sleep; I'll be taking lots of pictures of my set-up to share, and for critique.

    I'd like to make absolutely sure that I'm not doing something stupid and potentially ruining this wonderful gear. And thanks to everyone for the prompt responses, they've all been tremendously helpful. I'm really glad I decided to finally take the plunge and join tb.
     
  14. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Listen out for the speakers farting, try not to let them do that.
     
  15. When I play the RBA-500 with the Kustom cab alone, I do get a little occasional farting. I think that may be because my instrument cable is junk and is badly in need of replacement. I use a buddy's chord to test the hypothesis. I hope I'm not harming the 2x15 by having played with the crappy cable.
     
  16. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    a cable is gonna work or not work, pretty much.

    farting or distorting implies the speakers themselves are giving up.