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Question about using 3 cabs.

Discussion in 'Amps and Cabs [BG]' started by Biggbass, Jan 9, 2012.


  1. Biggbass

    Biggbass

    Dec 14, 2011
    Planet Earth
    I have two 15" cabs and a 2 x 10 cab. Each is an 8ohm cab. Using my Markbass LM3 amp would it be okay or not okay to daisy chain the two 15" cabs on one of the speaker outputs from the LM3, and use the other output for the 2 x 10 cab?
     
  2. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
  3. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Seweracuse, NY
    Or in slightly different terms, NO.

    The LMII will only allow for 2 8ohm cabs (for a total load of 4ohms), 3 8ohm cabs would present a 2.67ohm load and your amp would shut down if it works properly, or burst into flaming debris if not.
     
  4. butcher

    butcher

    May 24, 2011
    NO. The impedance of the three cabs would be below the minimum impedance of your head which is 4Ohms. The total nominal impedence fo the combination would be about 2.6Ohms. Markbass - Little Mark III

    You would need to use the line out into another amp to feed the 2x10 cab. This would also give you the opportunity to eq the 2x10 differently than the the 15s and adjust the volume level to balance with the 15s. Also, not as aesthetically pleasing, you will get a better tone if you position the 2x10 so that the two drivers are aligned vertically. Lot's of good threads in the amp section to this end.

    The two outputs on your amp are just wired in parallel (ie. the same as your jacks on the cabs). They do this for flexibility of connection, like if the two cabs you have only have one input jack. So, daisy chaining your cabs of off each other using one output from your LM3 is the same as using both outputs from your LM3 to each cab separately.


    Using the other speaker output on your head is no different than daisy chaining your 2x10 with your two 15 cabs.

    Info on combining speakers...
    Speaker Wiring Info
     
  5. Biggbass

    Biggbass

    Dec 14, 2011
    Planet Earth
    thanks all!

    that all makes sense...I suspected so...just wanted to make sure I wasn't over or under thinking it!
     
  6. butcher

    butcher

    May 24, 2011
    If you are willing to invest some time for research and a little $$ there is away to connect them all.

    You could build a crossover connection box and crossover the 2x10 with one of the 15s. That way, the amp will see the 15 and the 210 that are crossed over together as one 8Ohm load. Then when you add the other 15 it would be 4Ohms combined. This isn't the ideal solution but with some eq tweaking you might be able to get it sorted out properly.

    The key is to find the right crossover frequency. Probably somewhere in the 500-1,000Hz range.

    You either need to have all the TS specs and interior dimensions including port dimensions for all three of your cabs... or can get your hands on a two-channel power amp and a two-way active crossover.

    If you have all the specs (unlikely) you could plug them into WinISD and see where the 15s taper off on the high end and the 2x10 tapers off on the low end and find a crossover point that is in between them.

    OR If you have access to a reasonably powered two channel amp (not 100W per channel and not 1000W per channel) and a two way active crossover (a rack mount unit for example) and someone who knows how to connect them and run your the line out of your LM3 into the setup... you can adjust the active crossover frequency and play around until you find a setting you like. Then that is the frequency you will want to find.

    Sounds like a lot to go through, but it might be worth it...
     
  7. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    So might this:

    [​IMG]

    But there again maybe not. :D
     
  8. Mystic Michael

    Mystic Michael Hip No Ties

    Apr 1, 2004
    New York, NY
    LOL! :p

    MM
     
  9. butcher

    butcher

    May 24, 2011
    Ha! yeah - that's kind of what I was thinking too after I hit "post". :)

    Could be serendipity... or a big waste of time.

    The more I learn and tinker about amplification the more I appreciate the cost of a well-designed cab... and also why the less expensive stuff sounds the way it does.
     

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