1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  
    TalkBass.com has been uniting the low end since 1998.  Join us! :)

Question for the Ohmage Gurus.

Discussion in 'Amps and Cabs [BG]' started by Rowka, Aug 1, 2012.

  1. Rowka


    Dec 9, 2002
    Jacksonville, FL
    So now that I'm playing full time in a loud rock band again I'm finding that I could use some more stage volume.

    I have been running my Markbass CMP121 combo (same head unit as the older LM II, 1x12 8 ohm internal speaker that can be unplugged externally) together with a 1x12 8 ohm extention cab.

    I just got my old 2x15 4 ohm cab back that I would like to run under the MB.

    I tried it at practice for a short spell and it sounded freakin great. I'm worried though, that at higher stage volumes and for longer durations the 2.66 ohm load will let out the magic smoke from the MB.

    Acording to the MB manual, the amp puts out 300 W RMS at 8 ohms and 500 W RMS at 4. Of course, they say don't go below 4.

    So my question is am I really gonna let out the magic smoke?

    If so, can I up the load on the 4 ohm cab by putting a 4 ohm, high-wattage resistor in series with the cab?

    If not, should I consider rewiring the cab to 16 ohms and deal with the drop in output (will I still get a volume gain VS the single 1x12, 8 ohm extension cab)?
  2. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    You are playing amp Russian roulette. The Markbass heads have protection built in where they will likely just shut down when it gets to be too much, but you can't always count on that. If you don't like the way your stuff is built, get new stuff.
  3. I'd just run the 2x15 as the sole cab. Mic it up if you need more volume. 500 watts through a 2 x 15 should be plenty loud.
  4. Rowka


    Dec 9, 2002
    Jacksonville, FL
    It is plenty loud with just the 2x15. I just hate the idea of carying the combo and not using its speaker.
  5. On the combo plus extension cab, when you are using it with the rock band, are you hitting the limits of the speakers?

    Do you have the volume up to the point of clipping?

    If you are running the MB stack at full throttle, your only options are to either carry the combo and 2 x 15, or do as Jimmy said and change rigs.
  6. 1958Bassman


    Oct 20, 2007
    Would you rather hear the amp develop power, or waste it as heat? Heat is all a resistor gives you.

    Heat without any other byproduct is wasted energy. Better to use speakers that make the amp happy than to use the resistor.

    If you run it hard at 2.66 Ohms, you will cook your amp.
  7. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    Yep, skip the internal 12 (which would be not that significantly helpful anyway) and rock the 2x15 at the proper load.
  8. Dbassmon


    Oct 2, 2004
    Rutherford, NJ
    Get your cabinet at ear level and put the bass through the house system. Little Mark II though 2 x15 at 4 ohms should be pretty loud.

    Here is a novel idea, tell the band to turn down and your bass amp will seem louder. ; )

    Wear hearing protection, once your hearing is gone, its gone!
  9. will33


    May 22, 2006
    Ohmage eats cabbage and cabbage eats ohmage, therefor, if you have too much cabbage, you won't have enough ohmage. If you can survive with less ohmage, you can have more cabbage, but in your case, you need a little more ohmage and a little less cabbage, or your chi will be all out of balance.
  10. +1. While the magic smoke looks cool, it aint worth sacrificing a perfectly good amp over.
  11. Bitterdale

    Bitterdale Natural Born Lurker

    Dec 4, 2010
    Ocala, FL
    Just lay it facedown and it becomes an awesome head! :D
  12. Rowka


    Dec 9, 2002
    Jacksonville, FL
    If I rewire the 2x15 in series (16 ohms), what do I really lose?
  13. will33


    May 22, 2006
    Power handling/distribution. The 215 would get about 1/3 power and the single 12, 2/3. The farting 12 will limit how far you can turn up.
  14. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Exactly. Just accept that it's a bad idea all around and don't do it.
  15. Lol.. Sounds like a secret society of some sort... Beware " The Farting Twelve....." ....lol...
  16. gigslut


    Dec 13, 2011
    St Louis, Mo
    Would you rather carry the combo and not use its amp? That's where your going to end up if you insist on using it this way.
  17. will33


    May 22, 2006
    Could've called it the Dirty Dozen?...the Marks Templar?....the Bilderberg 12?....Skull-n-Bass?...

  18. Bradass


    Oct 17, 2011
    Tallahassee, FL
    Sell your combo and buy a LM3 head to pair with the 215 and you won't have to carry a useless 12 around anymore
  19. will33


    May 22, 2006
    You could rig both of your 12's in series and then parallel that to the series wired 215.:eek:
  20. Chazinroch


    Feb 2, 2003
    Ontario N.Y.
    I have MB 2X10 combo. Just 4 bolts holding the head in. Take the head out and save space and about 25 lbs.

Share This Page