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Continuous vs Programmable watt rating...

Discussion in 'Amps and Cabs [BG]' started by daveonbass, Apr 10, 2009.

  1. daveonbass

    daveonbass Supporting Member

    Apr 5, 2001
    Waupun, WI
  2. guido2sc

    guido2sc Guest

    Aug 9, 2007
    Jacksonville, FL
    RMS (continuous) is what you are looking for. Program & Peak are great hooks for manufacturers to pimp thier stuff. Peavey will tell you that you need to go with the "program" wattage but from my knowledge it's the RMS rating that you need to stay focused on. :bassist:
  3. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    +1 continuous is the same as an RMS rating, whereas peak and programmable are meant to infer the upper limits of the spikes, or very short bursts of power. RMS or continuous is the rating you want to pay attention to.
  4. daveonbass

    daveonbass Supporting Member

    Apr 5, 2001
    Waupun, WI
    That's kinda what I thought, thanks for the replies!!!

  5. I love some manufactures laughable attempts at the power rating misguidence thing.

    Like £5 computer speakers with "1000 watts P.M.P.O" that weigh less than packaging it came in.
  6. Bob Lee (QSC)

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

    Jul 3, 2001
    Santa Ana, Calif.
    Former Technical Communications Developer, QSC Audio
    "Program" power ratings are a loudspeaker manufacturer's roundabout way of saying "this is about the maximum amp power rating you should use," assuming that you don't run the amp into significant clipping. Program power ratings are usually about 1.5 to 2× the loudspeakers' continuous (i.e., thermal) rating.

    Continuous power ratings (often called by the misnomer "RMS power") describe how much power the loudspeaker can handle averaged over a period of time without a significant risk of the voice coil melting, adhesives softening and coming apart, etc. It is essentially a thermal rating. (Loudspeaker drivers typically waste well over 90% of the input power as heat and convert only a small amount into acoustical energy, making them about as efficient as incandescent lamps. Think of how much heat a 200-watt light bulb throws off when it's lit up, and you'll have a reasonable idea of how much heat the speaker's voice coil has to dissipate when you push 200 watts into it.)
  7. hrgiger


    Jan 11, 2009
    Exactly, the rule of thumb is have about 2x what the speakers RMS is for headroom etc. Which is why Peavey says to go by the program rating (a black widow is 350 rms, 700 program.) They do know what they are talking about you see, why people try to always know more than them about everything, I can't figure out...:rollno:

    These same people go only by the rms and send clipping signals to their BW's with underpowered amps, and blow them up (square waves destroy voice coils) and then blame Peavey for poor speakers. Give me a break...
  8. Just for the record it's program and not programable.

    As a rule of thumb IMO connecting a speaker to an amp with double its RMS rating is a recipe for blown speakers.

    And here we go again with square wave nonsense. A square wave is just a signal which a speaker will reproduce to the best of its ability just as it would any other waveform sent to it.

  9. seamonkey


    Aug 6, 2004
    Speaking of Peavey. Here's what they really say:

    Now they're talking PS speakers, and clipping can harm mids and tweaters as the power in to these drivers increases - it overpowers them.

    To clarify you need to dig into their other papers:

    And they have more on the technotes page:

    Peavey is consitent is saying it's too much power to the speakers that destroy them. It's not a clipped wave that destroys, it's too much power.
  10. Bob Lee (QSC)

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

    Jul 3, 2001
    Santa Ana, Calif.
    Former Technical Communications Developer, QSC Audio
    For most users, amp power of 2× the loudspeaker's continuous rating is a very good match. I would recommend though that inexperienced users who might not be as good at controlling their levels or noticing clipping should use higher-rated loudspeakers, even up to the amp's power rating.

    Square waves do not damage voice coils any more than other waveforms do.
  11. Thor

    Thor Gold Supporting Member In Memoriam

    Now you got me going. I just stated thinking off how to adapt
    a motorcyle oil cooler to cool my voice coil. Or add a compressor
    and evaporator to make my cab a 'fridge'.

    Also useful in keeping the beer cold.
  12. Bob Lee (QSC)

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

    Jul 3, 2001
    Santa Ana, Calif.
    Former Technical Communications Developer, QSC Audio
    Community, a loudspeaker manufacturer in Pennsylvania, had a speaker system line called the "Air Force" that used a fan in the cab to push air through ventilation hoses into openings in the back of the drivers' magnet structure, which would provide a cooling air flow over the voice coils. I don't know how well it worked or how successful it was. But cooling the voice coil is a major challenge for designers of high-power speaker transducers. The magnet structure and frame are the primary means of drawing heat away from the voice coil; the obstacle for heat transfer is that they and the VC cannot touch.
  13. Is their any specific reason why companies haven't widespread took to the idea of active cooling systems in cabs? Phase change cooling would be a funny thing to see haha, though not very practical!

    As above one named company has done this but was there an issue that stopped it from catching on?
  14. As I see it:

    Added weight
    Added complexity
    How do you make a sealed cabinet - you need an air flow
    How do you tune a ported enclosure - ditto
    Generally not needed in normal use

  15. seamonkey


    Aug 6, 2004
    In the JBL EON speakers, they use the port "wind" to cool the amp and drivers.
    You can see the cooling fins in the ports.

    Not sure why it's not done more often.

    Ports at the top and bottom of a cabinet could be used to create a chimney effect to keep things cooler.
  16. daveonbass

    daveonbass Supporting Member

    Apr 5, 2001
    Waupun, WI
    It's "programmable" according to Fender and/or Sam Ash: http://www.samash.com/webapp/wcs/st...man 115 1x15 Bass Speaker Cabinet-_-F23472000

  17. CodaPDX


    Feb 2, 2009
    It's my understanding that the acoustic output of the vast majority of cabs isn't limited by the thermal capabilities of the speakers so much as by the excursion of the drivers at low frequencies. Unfortunately for us, while speakers tend to come with some nice, easily quotable parameters to describe excursion (Xmax and Xlim), the tuning of the cabinet has such an enormous impact on the excursion at a given sound pressure level and frequency that it doesn't make any more sense to go around quoting the Xmax of your speaker cabinet than it does to tout it's thermal handling capacity. It's like quoting a microprocessor's speed: all other things being equal, more is better, but there are so many other factors that contribute to performance that quoting just a single number is meaningless.

    So in short, active cooling for cabs isn't worth the trouble and cost.
  18. what i dont understand is why worry about how close to failure gear can be pushed instead of adding more amp/speakers to the rig to allow for less strain on the gear.....surely a second amp/cab would be cheaper long term than melting down ones main rig
  19. Bassmec


    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    So its your considered opinion that the owners of 100 watt tube amps can feel perfectly secure and reliable and well equipped with just one of these:
    Sure you haven't been smoking them!:D
    I think it would take much of my rehearsal studio customer list about a couple of Brutal Truth covers to have the voice coil nicely melted and blistering.
    If you worked for Marshall you would be recommending a minimum of 4 Celestion speakers at a total handling of three times the total amp output in watts RMS.:ninja:
  20. Bob Lee (QSC)

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

    Jul 3, 2001
    Santa Ana, Calif.
    Former Technical Communications Developer, QSC Audio
    One of what?

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