Question about OHMS?

Discussion in 'Amps and Cabs [BG]' started by Madball, Aug 20, 2001.

  1. Madball

    Madball Guest

    Jan 11, 2001
    Dallas/FW Metroplex
    Ok here's the deal I just bought a SWR 1x15 cab to round out my speaker stack so I have this cab which is 200 watts @ 8 ohms and a SWR 4x10 cab that is 400 @ 8 ohms. My amp is a Crate BRX - 220, on the back there are 2 outputs one that is 220 @ 4 ohms and 1 that is 150 @ 8 ohms. Right now I am going out of my amp from the 150 @ 8 ohms to my 15 and then out of that into my 4x10.

    1. Is this that best way to maximize my wattage and thus my output?

    2. If not what would be the best way?

    3. Would I be able to go out of my amp through the 220 @ 4 ohms since my signal is going from one cab to the other? (Theoretically making it work at 4 ohms @ a peak 220...right?)
  2. Phat Ham

    Phat Ham

    Feb 13, 2000
    I'm not too familiar with the Crate amp you have, but I'm guessing the speaker outputs on the amp are parallel, meaning it doesn't matter which one (or both) you use. The "220 @ 4 ohms" and "150 @ 8 ohms" is just a label telling you the power at 8 and 4 ohms. The labels are not specific to a certain output jack. The way you are running your cabs now should be fine. You are getting the full 220 watts since the amp is "seeing" 4 ohms.
  3. EString

    EString Guest

    Nov 20, 2000
    Los Altos, CA
    Connect one cab to each output and you will get 220W @ 4 ohm (see above).
  4. CYoung


    Nov 30, 2000
    Gainesville, FL
    Let's see if I can muddy the issue a bit...

    As Mr. Ham says, the two jacks are actually both connected to the same power source (they are 'parallelled'). You can use one or both jacks, it makes no difference. The rating simply tells you the approximate maximum output power for a given speaker load. Most manufacturers provide two jacks so you can hook up multiple cabinets.

    1. Ok, you have two 8 ohm cabs: result -> 4 ohm load.
    2. Ok, your amp is rated 220W at 4 ohms: result -> amp can push a maximum of 220w TOTAL in the cabinets.

    Now, you might look at the numbers and go EEK! I am pushing 20W more than the SWR cab can take. Don't worry. If you have two cabs of equal impedance, the power will roughly (the math on this is too freaky to post here, let's leave it at roughly) split 50/50. This would mean each cab is getting about 110W max. Result -> each cab is well below its designated max power. Frankly, this is a very popular and nice-sounding setup for most folks.

    You may want to upgrade that Crate head one day, though. ;)