RMS? Program?

Discussion in 'Amps and Cabs [BG]' started by whofan, Jul 1, 2001.

  1. whofan


    Jun 29, 2001
    take this for example:
    175 Watts RMS continuous @ 4 Ohms
    350 Watts Program

    ok, say you have... a 350 watt head at 4 ohms and a cabinet with those ratings above. .....what does that mean for you?

    moreover, what does RMS mean? and what about program?
  2. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    "Program power" is a speaker manufacturer's roundabout way of saying "an amp of this power rating will let you push these speakers to the maximum safe and usable level, without having too much power left over, and without significant clipping on peaks and transients." You didn't know one word meant all that, did you?

    "Continuous power" is how much average power the speaker can withstand over long periods of time without sustaining damage.

    "RMS" means root-mean-square, and it's a method of measuring AC voltage or current. It really isn't applicable to power, because RMS voltage times RMS current equals average power. It's commonly assumed to mean "continuous" in power ratings, but in actuality you can do an RMS calculation on any portion of a waveform, whether it's a long or short time period, even milliseconds (some makers of wimpy amps have done power ratings on short tone bursts to give them inflated "RMS power" ratings). So don't put too much faith into "RMS" power figures unless they're more fully defined as being "continuous."

    If it ever comes up, "peak" power ratings are mostly useless.