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Underpowering speakers?

Discussion in 'Live Sound [BG]' started by Andy419, Nov 27, 2008.

  1. Andy419


    Aug 13, 2007
    My band just got a new PA and my dad, who has had a lot of experience with live sound in his day, warned me not to "underpower" the speakers as that can blow them just as overpowering them can.

    So I was at the first band practice with the new PA and was working with it and decided to throw the power to just one speaker in order to prevent "underpowering" since we weren't playing all that loud, and of course my guitarist throws a little tantrum (which he does whenever things don't go "his" way) and did his little 'don't talk to anybody and have a pissy attitude' routine because he said "Why did we get this new PA if we can't use all it's power?" (Because we are just PRACTICING, DUH!)

    So basically I'm just looking for some concrete proof that underpowering can blow speakers to put in his face so he will shutup and realize it could kill the speakers.
  2. RustyAxe


    Jul 8, 2008
    The issue isn't one of too little power to the speaker ... per se. Speaker will not be harmed by running the amp at low output settings.

    The issue is an underpowered amp trying to drive a speaker to max volume. The rule of thumb is that the power amp should be capable of TWICE the rated watts of the speaker. I know, this sounds counterintuitive. But here's the logic ... to get more volume there's the temptation to increase the output of a weaker amp ... often to the point of clipping. It's the CLIPPING of the amp that can have ill effects on the speakers. A more powerful amp can produce the same loud volume without clipping (that's called having "head room") and will drive the speakers cleanly.

    So ... if you are driving your speakers at the desired volume (whether that be quiet or loud) and are not clipping, you're fine.
  3. Stumbo

    Stumbo Wherever you go, there you are. Commercial User

    Feb 11, 2008
    Intergalactic Mind Space
    Song Surgeon sofware rep.
    richspillberg likes this.
  4. I'll buy this premise in the "Live Sound" heading of twice as much amp as speaker handling. Just don't "loan" the system to recorded music like Techno, heavy in square waved effects the thermal limit of the speakers will easily be exceeded. Don't try this premise for live bass guitar.
  5. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    God, these falsehoods will just never die.
  6. GregShadoan


    Sep 1, 2008
    You won't find any. While it is true, that pro audio companies use bigger amps (50%-TO 100% more) then the speakers are requiring, it is for headroom. Speakers blow. Period. Nothing anyone can do about it. They wear out, or just plain old blow up. I have never been able yet to blow a 600 watt driver using a 50 watt amp. Just sounds like arse.
    The only way a smaller power amp will blow a speaker up is if it malfunctions in some way, from perhaps being driven too hard. Cliping (in pro sound) is always bad. If you have 2 speaker cabs rated at 300 watts each, you should be able to power them up with an amp that will deliver 200-600 watts at the rated ohms into that speaker and you should not have any problems. Having said that, your speakers will get old, wear out, or blow up, eventully. Again, nothing you can do about it. It may take along time.