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Help understanding Ohms

Discussion in 'Amps and Cabs [BG]' started by matty4string, Sep 27, 2017.


  1. matty4string

    matty4string Inactive

    May 11, 2016
    if I’m running two 8 ohm Acoustic b115 cabs into 1 acoustic b200h head at 4 ohms at 200w. What is the total wattage and ohms thank you .
     
  2. bholder

    bholder Affable Sociopath Supporting Member

    Sep 2, 2001
    Vestal, NY
    Received a gift from Sire* (see sig)
    Depends on how they're connected. Standard parallel connection, you'll get 4 ohms and 200 watts. Connect them in series instead and get 16 ohms and 50 watts (if the head will even do that).
     
  3. matty4string

    matty4string Inactive

    May 11, 2016
    They are in parallel the cabs are 250 Watts if I run them parallel should I not get 500w if I used a 500w head
     
  4. bholder

    bholder Affable Sociopath Supporting Member

    Sep 2, 2001
    Vestal, NY
    Received a gift from Sire* (see sig)
    Well sure, the cabs' power rating is their power handling capacity, a head that can do 500 watts at 4 ohms should get you the full 500 watts' worth of sound.
     
    matty4string likes this.
  5. Raf Seibert

    Raf Seibert

    Dec 16, 2013
    Texas
    CAN give you the full rated power. If you don’t have the amp turned up, it won’t. If you have it turned up, but you’re playing softly, it won’t. These numbers aren’t carved in stone, if you don’t send a full strength signal to an amp that’s turned to maximum output, you won’t get full power. That’s probably a good thing, many times.
     
  6. The power rating on an amp tells you how much power the amp can produce.
    The power rating on a cab tells you the max power you should use to drive the cab.

    NOTE: This is the simplistic explanation and should address your question.
    There may be other considerations that one would want to consider, but that is beyond the scope of your question.

    Two cabs rated to handle 250 watts each will handle a total of 500 watts.
    The power output of the amp is limited to it's max power rating at the lowest operating impedance. As in 200 watts @ 4 ohms.

    In your case you have a 200 watt @ 4 ohm amp and connect a pair of 250 watt cabs that are 8 ohms each.
    The amp can supply up to 200 watts total, 100 watts to each cab.
    Your cabs should loaf along nice and happy because each is rated for 250 watts.
    The difference between how much power the cabs get and how much they are rated to handle is the headroom.
    It's always nice to have some headroom in your system and not drive the cabs right at their limits.
     

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