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overpower or underpower, a hypothetical..

Discussion in 'Amps and Cabs [BG]' started by Eilif, Feb 2, 2006.


  1. Eilif

    Eilif Supporting Member

    Oct 1, 2001
    Chicago
    If you had
    an Avater 2x12 cab rated for 1200 watts rms, and the choice of two power amps (I already have a good pre).

    Would you take the amp rated for 1000 watts or the amp rated for 1500 watts?

    Thanks
     
  2. I would go for the amp with 1500 watts... I would rather have more power in case you want to swap out cabs later. I tend to always go with a 'bigger is better' mentality. I know this isn't always true, but it is my normal habits.

    Oddly enough -- I played a show with another band last weekend & their bassplayer was trying to explain to me that if you underpower your cabinets - this is what leads to blown speakers.... which completely seems backwards. I still don't think I understand that scenario.
     
  3. are we assuming they're the same company and line??

    If so, then I'd say 1500 assuming it wasn't a drastically larger weight.
     
  4. WalterBush

    WalterBush

    Feb 27, 2005
    Yuma, Az
    That's because the idea is ridiculous. I drastically underpower cabs because all the cabs I own are huge, and I don't usually play to SRO 5000 person crowds. Speakers blow because they get pushed too hard and the voice coils overheat, or they get pushed too hard and the cones flap apart, not because there's not enough signal going into them.
     
  5. Eilif

    Eilif Supporting Member

    Oct 1, 2001
    Chicago
    Not the same line. I want to use a my ampeg pre into a carvin power amp, into an avatar 2x12 1200watt cab. The carvin power amps come in 1000 and 1500 watt models.

    So, should I get the 1500 or the 1000 watt model....
     
  6. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    No, it isn't, drivers are routinely damaged by clipped waveforms due to underpowering, but it's almost always limited to tweeters and midranges, very seldom does it happen in woofers.
     
  7. +1

    I don't think that you will ever need more than 1000w (?) so I would just save some money and get the 1000w power amp.
     
  8. Underpowering is a misnomer.

    I think it is important to point out that the problem here isn't in using less power than the speakers are rated for. The problem is clipping an amp that is too small for the job.

    What damages the drivers is getting too much power, not too little. A clipped amp produces too much high frequency energy for the high frequency drivers to handle, not too little. They are overpowered, not underpowered.
     
  9. Sundogue

    Sundogue

    Apr 26, 2001
    Wausau, WI
    I think what gets people confused is this...

    If you use too small of a power amp (underpowered) and drive it to clipping in an effort to get louder, you'll fry your speakers. Not because the amp is too small (underpowered) but simply because it's being driven too hard.

    If you use a big, powerful poweramp (overpowered), you never have to drive it too hard to get the same volume.

    So it appears that underpowering your speaker cabs fries speakers. There is a bit of truth to it, but it really doesn't tell the whole story.
     
  10. What i meant was between the poweramps are the same maker...I'm looking at the carvin DCM1500 vs. 1000 ... same line ... but anyways, for a difference of 70 bucks and 7lbs? I'd get the 1500 for sure.

    Don't know if you're for sure always going to bridge, but if in the future you were to get a diff speakers or whatever, the 1000 at 300w per channel is ok, not great. I'd for sure go for the 1500 with 500w per channel.
     
  11. Herman

    Herman

    Dec 25, 2005
    Lynchburg, VA
    But you can also blow your speakers with an amp that's putting out too much power for them to handle - even if it's a clean signal (i.e. not clipped).
     
  12. No speaker was ever blown with less power than it could handle.....:D
     
  13. Sundogue

    Sundogue

    Apr 26, 2001
    Wausau, WI

    Yes, but I was just referring to the point that underpowering speakers blows them.
     
  14. Herman

    Herman

    Dec 25, 2005
    Lynchburg, VA
    My point was that simply buying an amp that has a rated power ouput greater than your cab's power handling spec is no guarantee that you won't ever blow your speakers.
     
  15. Absolutely.

    Just as using an amp rated for less power than your speakers is no guarantee that you won't blow them..... To a point anyway. Obviously, you're not going to blow up a 500W rated speaker with a 10W amp no matter how hard you push it. But clipping a 400W amp into the same speaker could get you into trouble....
     
  16. As for the original question:

    I doubt that cab could actually handle 1200W for any period of time. But let's operate assuming it can....

    Due to the dynamic nature of music, you never really end up putting the full power of an amplifier into a speaker on an average basis. So 1500W of amp power would actually be a pretty decent match for that cab. There wouldn't be any issue with 1000W either. In terms of overall output, there won't be much difference. I think that people should typically get as much power as they can afford, so if you can swing it, go for the 1500W amp. Either amp, driven hard would have the potential to damage the speakers, but under normal operating conditions (even with the odd clip light flash) you should be fine with either.
     
  17. Eilif

    Eilif Supporting Member

    Oct 1, 2001
    Chicago
    late reply, but....
    I just wanted to thank everyone for thier input. I hadn't really given much thought to future use of the cab, but the greater watts for driving 2 cabs unbridged is definately something I will keep in consideration. I think when I get the $ together I will definately spend the extra 70 bucks and get the 1500 watts, now that I know it is safe.

    I've been playing out of smaller combos (250-300 watts) for so long, that it is exciting to think of being able to have the headroom to crank up a bit without worrying about clipping the amps.
     
  18. Pickebass

    Pickebass Supporting Member

    Jul 12, 2004
    San Antonio, TX
    This is probably the closest to the truth. However, a 1000 watt amp in no where close to "underpowering the cab. If you are pushing a 1000 watt up to the point of clipping and frying the speakers, you probably need another speaker cab to push more air.
    Either amp should be great to solve your problem. If the extra wattage is not that much more, I would probably recommend the bigger of the two. But you can't go wrong with either choice for the one cab.
     
  19. ricplyrz

    ricplyrz

    Dec 26, 2005
    Wrong> A clipped amp does not allow soft and loud passages of the signal. It "compresses" the signal to a constant level, thus not allowing the speaker any time for cooling.


    billfitzmaurice..since he is a talented speaker designer and makes his living at it, must surely be wrong!! He and I have disagreed, but I have never disrespected his knowlodge.

    Speakers are damaged due to clipping. That means the waveform (usualy a sinewave) turns to squarewave. Hence the term "clipping" as in, the tops of the wave are "clipped" off. Thus turning an alternating signal into a dc voltage basicly.

    This "constant" voltage, does not allow proper speaker voice coil cooling. Then you get a fried speaker.

    Tweeters are the first to go, since they take the least amount of power, then midrange and woofers, as Bill pointed out.

    Now in a bass bottom application, where most bottoms use only woofers, (disregarding the tweeters on newer bottoms) if you UNDERDRIVE a speaker with a distorted signal...it WILL fail.
     
  20. seamonkey

    seamonkey

    Aug 6, 2004
    It depends.

    Let's say you ran low E into clipping to produce a square wave over 10 seconds.

    If you follow the Fourier transform theory a square wave is a build up a multiple frequencies. So a 41 Hz square wave includes the fundamental and many mid and hi frequency components.

    If you have no tweeter, and woofer can't reproduce these mid/high frequencies the energy needs to go somewhere - so it's usually dissipated as heat.
    If you have a woofer that can't handle highs, and you like to clip, you could add a crossover to a dummy load for the higher freqs.

    If you have tweeters and mids, the amount of power going to them from the high frequencies components of the square simply overpowers them and they blow. If they open, then you're back to the energy has to go somewhere ...

    Also most amp power supplies are going to drop their rail voltage when clipping since they can't maintain DC at that level.
    A 100W amp at 8 ohms would need a rail voltage of at least +-28V Volts and 3.5 Amps. But the power supply isn't going to maintain this and the amp is going to drop in wattage.

    Something else that happens on bad SS designs (which probably no longer exist and haven't for years). When clipping, the feedback destabilizes and amps add a lot of distortion adding even more high freqs. But even the cheapest amps out there have limiters on them to prevent this.