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under-powering?

Discussion in 'Amps and Cabs [BG]' started by katri, Mar 11, 2006.


  1. hi,
    i am thinking of getting either a schroeder 1212 (1000watts) or a 1210 (850watts) and pairing the cab with either an ampeg B-2RE or aguilar AG 500 (this is not about the amp choice though) would i hurt either the cab or head by powering a 1000w cab with around 500w if so could someone pleases explain why. i understand why overpowering would damage speakers/cabs but why under powering?
    many thanks
    Dan
     
  2. PotsdamBass8

    PotsdamBass8 Supporting Member

    Jan 23, 2005
    As I understand it, underpowering hurts because the power amp starts clipping. This is if the amp can't put out as much power as you're looking for, and you start turning up a lot. I don't think it would be a big concern for you with those amp choices. If you were powering a 500 watt cab with 100 watts, that would be of bigger concern, since you'd likely be turning the head up near max.
     
  3. +1 Underpowering a cab is never a problem unless you are turning the amp up so loud that it clips... and that has nothing to do with the cab rating anyway... so it's a zero issue. The key is to match the power rating and efficiency (SPL) of the cab to your volume needs... so that you are not pushing an amp to put out more sound than it's designed to do. The Schroeders are very, very efficient... so 500 watts or so into a medium 4ohm Schroeder will sound wonderful.

    We actually tried the Ag500 with my 4ohm Schroeder1212 at Vic's house a while back and it sounded GREAT... warm, loud and punchy.
     
  4. seansbrew

    seansbrew Supporting Member

    Oct 23, 2000
    Mesa AZ.
    +1 I power all of my Schroeder mediums with 500 watt amps. I have not run out of head room with any of my amps. This was a concern when I first got these cabs. I was considering getting rid of my QSC PLX 1602. It puts out 500 watts per side @ 4 ohms. But so far this amount of power seems to be enough. I may upgrade later, only if I need too.
     
  5. thanks for the responces guys. i understand a hell of a lot more now. thanks
     
  6. Crockettnj

    Crockettnj

    Sep 2, 2005
    North NJ
    I think it may be safe to say that there is no such thing as underpowering. Now, i may be wrong, but i leaning towards being pretty sure of this.

    Give me an example of classic "underpowering" and i think it's just a matter of turning the amp up too much. turn it down, you are powering the cab EVEN LESS, and its not underpowered at all.

    It's a volume issue, no?

    Oh, and of course it's semantics!

    ;-)
     
  7. seansbrew

    seansbrew Supporting Member

    Oct 23, 2000
    Mesa AZ.
    It comes down to running out of head room. Attempting to draw more power than an amp can produce leads to clipping. This is dangerous for speakers. I have underpowered pa speakers before and ended up blowing all the speaker fuses. I needed more volume for that show. I ended up purchasing a more powerful amp and did not have this problem again. So I would say that if you want to use a high rated cabinet to its full potential, give it the power it requires.
     
  8. Herman

    Herman

    Dec 25, 2005
    Lynchburg, VA
    A cab doesn't "require" a certain amount of power. The power spec on cab's is a power handling figure.

    To the thread-starter: if you want all the details on the topic of "underpowering" a cabinet, see this thread (at least the last 4-5 pages of it):

    http://www.talkbass.com/forum/showthread.php?t=227451&highlight=underpower
     
  9. ibz

    ibz

    Apr 14, 2005
    Columbus, OH
    Like its been said already many people here use rigs that you would think would be "underpowering" the Schroeder's, but really not.

    I wouldn't worry about it, I think its a non-issue.
     
  10. ghindman

    ghindman

    Feb 10, 2006
    Yeah, it's a volume issue. A cone will reproduce a signal with a very very small amount of power, especially higher frequencies that require little extension, the question is can you deliver enough power to get the volume you need.
     
  11. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    It wasn't because you underpowered your cab. It's because you were underpowered for your gig. The key is having a big amp; once you have a big enough amp, cab power handling is all but irrelevant to headroom, as long as the cab can handle at least the percentage of the amp's rated power that you're actually using.
     
  12. Dbassmon

    Dbassmon

    Oct 2, 2004
    Rutherford, NJ
  13. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
  14. Dbassmon

    Dbassmon

    Oct 2, 2004
    Rutherford, NJ
    I think what they are saying is not at all in disagreement with my statements. They are talking about the two ways to take out speakers are overpowering where the excusion of the cone exceeds the rated spec. and quality of power where clipping occurs. Those two notions are exactly what I am talking about.

    Don't take my word for it
    http://www.rane.com/note128.html
    http://www.rocketroberts.com/techart/powerart_a.htm
     
  15. seansbrew

    seansbrew Supporting Member

    Oct 23, 2000
    Mesa AZ.
    Good stuff guys, I have alot to learn about this subject as well.
     
  16. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    Agreed that there are two ways of taking out speakers, overpowering and overexcursion. But the application of the concept of DC voltage in the context of clipping is not correct. As Bob said in the other thread, clipping is not DC, nor is it like DC. And clipping doesn't *in itself* take out speakers, as any guitar player knows; it does so only when it leads to overpowering or overexcursion, both of which can also happen without clipping.
     
  17. Dbassmon

    Dbassmon

    Oct 2, 2004
    Rutherford, NJ
    See the references I posted above. One is from the Rane Power amp company. They support my position as does the other reference.
     
  18. Crockettnj

    Crockettnj

    Sep 2, 2005
    North NJ

    agreed
     
  19. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    Actually, they don't. Neither supports your idea of clipping creating DC voltage, and neither supports the idea that clipping is inherently bad. It's bad when it results in one or more components of a cab receiving more power than they can handle or being forced to move more than they're capable of moving, and not until then.
     
  20. Dbassmon

    Dbassmon

    Oct 2, 2004
    Rutherford, NJ
    If we were to apply the signal illustrated in Figure 4 to a speaker, the sound would take on a "harsh" or "raspy" sound. The sound quality will deteriorate further the more the signal is clipped. In extreme cases, a sine wave will approach the shape of a square wave when clipped. Clipping introduces a large number of what are known as harmonic components to a signal (and it also increases what is known as the RMS level of the signal, something that can lead to blown speakers).

    The graph they refer to (exactly the same graph I drew) shows the exact wave form the speaker should emulate. If there is power applied across a straight line, which it is, that is the definition of DC voltage. It is not alternating. You are entitled to differ, of coarse but I think I said all I can on the subject.