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Another ohms question

Discussion in 'Amps and Cabs [BG]' started by bluefishgd, Sep 1, 2003.


  1. bluefishgd

    bluefishgd

    Oct 26, 2002
    Rhode Island
    ok, let's say i have a firebass that can push
    700w@2ohms
    500w@4ohms
    275w@8ohms
    if i have a 2x10 cab that is 8 ohms, and i wanna add another 8 ohm cab, it obviously makes a 4 ohm load. But what would happen if i added a 4 ohm cab to the 8 ohm cab...would it run at 6 ohms???
     
  2. 2.67 ohms
     
  3. Nope, the result would be 2.67 ohms. Mathematically, take the reciprocal of 4 ohms: 1/4, which equals .25 then find the reciprocal of 8 which would be .125 add the two together for a total of .375 then take the inverse of that which gives you 2.67 ohms.....Easy huh?

    Or think of it this way: the 4 ohm cab probably has two 8 ohm speakers in parallel, add a third 8 ohm speaker in parallel so now you have 8 ohms divided by 3 which equals the aforementioned 2.67 ohms.

    BTW you don't want to do this in practice for two reasons: first, the load on your amp is too low, and also the power is unbalanced across the speaker cabs. The 4 ohm cab will see almost all the power, the 8 virtually nothing.
     
  4. The calculation is 1/Total resistance= (1/R1)+(1/R2). However it wouldnt be a good thing to mix these cabs due to different sound levels unless you had a stereo power amp.