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Head and cabinet wattage/amperage matching

Discussion in 'Amps and Cabs [BG]' started by bigcardinal, Apr 3, 2006.

  1. I am a complete greenback when it comes to the issue of matching an amp head with a cabinet(s). I am terrified that by making some silly little mistake I will destroy some expensive speakers. But, alas, it is time to upgrade to a bigger setup. Here are my questions:

    1) If you are running only ONE cabinet, does it have to be at least the same wattage as the head? (assuming the ohms are the same). Will a 400w(8 ohm) head will require a minimum of a 400w(8 ohm) cabinet?? AND a 400w(8 ohm) head will FRY a 300w(8 ohm) cabinet?? Or will this only happen if it is driven at very high volumes??

    2) If you run TWO cabinets out of one head, what are the amperages meant to be?
    Question: A 400w(8 ohm) head will drive
    a) TWO 200w(4 ohm cabs)??
    b) TWO 400w(4 ohm cabs)??
    c) TWO 200w(8 ohm cabs)??
    d) None of the above!!!!

    Please help me out if you can.Thanks!!
  2. jokerjkny


    Jan 19, 2002
    NY / NJ / PHL
    what you ask is in the sticky FAQ,

    but you should always have MORE power in your amp than what your speakers can handle.

    pushing an amp to its limits, especially one w/ a solid state power section, will force it into clipping, which'll send square waves into your speakers, thus ruining them.

    having the "headroom" that only extra wattage gives you, prevents that from happening. also, there are more instances of guys destroying speakers from underpowering than overpowering.
  3. thanks for the re-direct guys....that sticky post helped out a ton!!
  4. Joker, if you caught the many interminable threads on clipping etc that have been created in this forum over the last coupla years, you'll remember that many of these assertions have been refuted many times here, notably by Bob Lee and Mark Reccord. Clipping doesn't automatically lead to square waves; square waves aren't inherently damaging to speakers; instances of "underpowering" destroying speakers generally turn out to be overpowering in a sense (because a clipping amp devlops much more than its rated power); and headroom isn't created by having more amp power than the cab can handle (the cab's power handling is not directly relevant to headroom) but by having more amp power than you need for your *gig* (which is not the same thing at all).

    I think it's truer to say that you should always have more power than you need *for your playing situation*, so that you don't regularly use more than a percentage of your amp's power, and you should always have at least enough cab power handling to handle the fraction of the amp's power that you do regularly use.

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