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run 4 ohms into 8 ohm cab?

Discussion in 'Amps and Cabs [BG]' started by downstairs, Oct 18, 2001.


  1. downstairs

    downstairs

    May 13, 2001
    Pasadena, MD
    saying i did try this (not yet) what would happen? My cab is rated at 375 at 8ohms, my amp head is 300 watts at 4 ohms, what would happen if i did try this?
     
  2. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    The power rating applies when hooked to a 4 Ohm cab.
    Usually you can use any cab that has an impedance of 4 Ohm or higher (some amps handle loads of 2 Ohm, but 4 is the standard).

    It's no problem at all to hook a 8 Ohm cab to your amp, but it'll deliver about 30% less power than @ 4 Ohm.
     
  3. Your amp will put approximately 150 watts into the 8 ohm cab. No damage, no worries.

    Caveat: this assume a solid state amp. If a tube amp, you must have an 8-ohm tap to run an 8-ohm load.
     
  4. downstairs

    downstairs

    May 13, 2001
    Pasadena, MD
    no, i wanted to try and run 4ohms some way into my 8 ohm cab, what woulda happen?
     
  5. danny3k

    danny3k Guest

    May 26, 2001
    Aguadilla, Puerto Rico
    What do you mean with tap??
     
  6. Matthias

    Matthias

    May 30, 2000
    Vienna, Austria
    You do not 'run Ohms into a cab'. Ohms is the measuring unit for the impedance of the cab.

    An amp puts out power (Watts). The higher the impedance of the cab hooked to the amp, the lower the power output. (The cab 'impedes' the flow of current, so to say)

    And if the impedance of the cab(s) is too low, too much current will flow and the amp will smoke off sooner or later.

    With all-tube amps things are a little different: The cab has to match the head exactly. To be able to run the amp at different loads, there is either a selector switch or different speaker outputs for 8/4/2 Ohms.

    Matthias
     
  7. Tube power amps had different transformer taps (connections) that allowed the tube output to run with various different speaker impedances. The intent is to closely match the power amp impedance to that of the cabinet.

    A solid state power amp has no taps. It is designed to operate with a specificed minimum impedance, and works fine with impedances higher than the specified minimum. For example, my QSC minimum impedance is 2 ohms. I run an 8 ohm driver and it is fine. If I had a tube power amp, I would use the 8-ohm tap to connect my 8-ohm cabinet.
     
  8. danny3k

    danny3k Guest

    May 26, 2001
    Aguadilla, Puerto Rico
    THANX!!!