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RMS & Program

Discussion in 'Amps and Cabs [BG]' started by spectorbass83, Oct 27, 2005.


  1. spectorbass83

    spectorbass83

    Jun 6, 2005
    canada
    What does it mean when a cab has "400W RMS and 800W program"? What is the difference between RMS & Program exactly?
     
  2. The output on amps is usually shown as RMS, so thats the one i always use to reference a cab against an amp

    I think program is the same as peak, if its not, i dont know, someone more knowledgable about that will come along, but RMS is what counts
     
  3. tadawson

    tadawson

    Aug 24, 2005
    Lewisville, TX
    RMS is long term power handing, what the cabinet can essentially handle forever. Program power is VERY short duration peaks that the cab can tolerate, but that if sustained for a longer period would destroy the cab. Back in the 70's, there were some issues (and maybe laws . . . ) regarding rating audio gear, in that some companies were getting creative and using "program power" to inflate ratings of products, ("This cab can handle 47,000 watts!" [But no mention that it was only for 1/10000000 of a second or a fire would erupt . . . ]).
    As such, a lot of folks consider "program power" to be a bull**** ratiing, bordering on fraud . . . . . . the RMS is the one you want to use primarily when matching amps to cabs.

    - Tim
     
  4. spectorbass83

    spectorbass83

    Jun 6, 2005
    canada
    Thanks for the quick reply. I was just on Musicians Friend and it looks like they ship to Canada now :hyper: so I wanna get some questions aswered before I spend some money. Pretty Excited!

    Cheers
     
  5. spectorbass83

    spectorbass83

    Jun 6, 2005
    canada
    :eek: 47,000 watts eh? LOL come on. I'm sure you would need an amp that goes to 11 for that!

    You answered my question, thank you! Now if only I could decide on which cab/head I want :D
     
  6. PC speakers are bad for stuff like that, the ones sitting infront of me are apparently 1500 watt, which i think is pretty immense :p

    Good luck picking your head and cab

    What kind of music do you play, who do you play with (their equipemnt anyway), and what kind of budget you got ? we might be able to help :)
     
  7. spectorbass83

    spectorbass83

    Jun 6, 2005
    canada
    1500 watt computer speakers :eyebrow: LOL nice!

    The music my band plays is mostly hard rock. There are 2 guitarists - the lead guitarist plays through a behringer 4x12 powered by a Peavey 100W head, the 2nd Guitarist/vocalist plays through a Line6 2x12 combo and to top it off we have a loud drummer!

    I am currently playing through a 200W Yorkville 2x10 combo which is good for practice, especially with the help of the preamp in my Zoom multi effects pedal. For medium-large venues I need more power! Especially if there is no PA support.

    I am looking into spending about $1500 Canadian...Although if I go over my budget a little bit, it won't hurt. As long as I can find something dependable. Lately I have been looking into 4x10's but I wanna add a 1x15 in the long run, so this is making it a little tough to decide which amp I want. If I get a 4 ohm cab and decide to add that 1x15 later, I will need an amp that goes down to 2 ohms. Which brings me to my little dillema - 4ohm or 8ohm?
     
  8. I used to be on the big speaker band wagon, but I think the 412 is the best all around speaker combination (IMHO) if you want only one can, although nothing can shack the floors like at 18, the 12's sound very nice to me, good low end, very punchy, and since I have my horn turned off the highs are their and sound very nice. although my 150 lbs price tag inst comforting its worth it for the tone.
     
  9. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Richland, WA
    RMS is what your cab can run all day, every day...using a test tone. A very rugged rating. THE ONE to go by.

    Program is roughly RMS times 2. It is based more on gig/music event timeframe and takes into account dynamics in music. Reasonably safe to go by as long as you don't push your rig very hard.

    Peak is based on a VERY short ime frame. It is the maximum power your speaker can stand at one extremely short time period and not blow. Think a kick drum or a slap on the bass.

    It used to be all you ever saw rating wise was RMS and Peak. At the time, Peak was always twice that of RMS. Then the Program rating came in using the arguement that unlike a test tone, music is dynamic and although it can get very loud in some passages it can also get very soft, in the same piece of music.

    I am not sure if Peak got extended or RMS got lowered but typically today (Yes, I still occasionally still see exceptions) you have:

    Peak = Program times 2 or RMS times 4.

    Program = 2 times RMS or 1/2 of Peak.

    RMS = 1/2 of Program or 1/4 Peak.

    If you want my advice, always go RMS where you have a choice.

    Much better to be safe than sorry.

    :D

    Joe.
     
  10. 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
    "RMS" is a misnomer for "continuous average" power; technically there is RMS voltage and RMS current, but "RMS power" is impossible. Anyway, it's basically a thermal rating of how much average power the loudspeaker can safely handle without risk of damage.

    Loudspeakers can handle short peaks and bursts that are higher in power than their continuous rating, though, as long as the overall average power doesn't exceed it. This is useful because normal audio, like music, voice, etc., isn't made of continuous, unvarying tones, but instead has dynamics, or variations in loudness. That's the basis for the common rule of thumb of choosing amp power that's about 2x (some recommend 1.5x to 2x) the continuous average power rating of the loudspeakers (as long as you don't incledw signal frequencies that are too low for the loudspeaker to handle); this is typically the same as the speaker's "program" power rating.
     
  11. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Richland, WA
    Good info.

    Thanks Bob.

    :D
     
  12. RMS = Root Measured Squared
    Root being the square root of the mean amount of power. Which is an average based off a 10 hr. duration of time. If proper reference testing was done.

    Another note to bare in mind. Wattage = voltage x amperage. As stated earlier by another tb'er. Both will vary. And alter the themal load. Voltage is penitrating power. Amperage is the current.

    And that is often why it's recommend to treat tube power like 2x FET power. Due to higher voltages. It's more able to burn out voice coils.

    I fogot to note this orginally. Program power. Is usually a burst measure (more than one cycle). Of 2-4 cycles, depends on manufactures rating. Where as peak power for an amp is usually a single cycle measure.
     
  13. Cool, cheers for that Joe, i always thought peak and program were the same thing :)
     
  14. Bassstud1

    Bassstud1 Supporting Member

    Sep 23, 2001
    LaPorte Indiana USA
    RMS is = 1/2 the (square root of 2) times peak power
    EX. Peak power = 100, RMS = .5 * 1.414 *100 = 70.7 watts

    Some amps used to be rated at peak to peak power.

    so an amp that was actually a 200 watt RMS amp would be advertised @ 565 Watts of PURE POWER

    200 * 1.414 =282.8(Peak Power) 282.8 * 2 = 565.6 ( Peak to Peak)

    Hopefully this formula is still the same as I remember from my electronics classes it's been a while I studied vaccum tubes and we used slide rules ( Pickett rules) <-- for you old timers.
     
  15. 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
    Fixed. ;)