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Underpowering! The REAL skinny!

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Underpowering! The REAL skinny!

  • On a recent post, I noticed it was mentioned that underpowering a sub can cause said sub to blow. I was most surprised at how this myth is still floating around.

     

    If you could blow subs by underpowering them, there would be no subs in existence since simply turning the volume down IS underpowering them.

    Underpowering is often confused with clipping.

    Clipping is one form of distortion that occurs when an amplifier is overdriven, which happens when it attempts to increase voltage or current beyond its limits. Clipping can also occur at the source level and being sent on down the line to the speakers.

    When an amplifier is asked to create a signal greater than its maximum capacity, it will amplify the signal only up to its maximum capacity, at which point the signal will be amplified no further. As the signal simply "cuts" or "clips" at the maximum capacity of the amplifier, the signal is said to be "clipped." The extra signal which is beyond the capability of the amplifier is simply cut off, resulting in a fixed signal. Note that this fixed signal suffers from other forms of distortion, such as total harmonic distortion.

    The clipping introduces additional high frequency components, meaning the clipped signal will be weighted more towards treble than the unclipped signal. Some people believe this additional treble weighting is dangerous to tweeters. Others believe that it is not dangerous, noting that normal music recordings sometimes have significant treble energy and yet don’t damage tweeters.

     

    ----------

    I can drive speakers with a 100% clipped square wave signal all day long with no problems as long as the thermal and mechanical limits of the speaker are not exceeded.

    I can feed a speaker 100% distortion all day long with no damage as long as the thermal and mechanical limits of the speaker are not exceeded.

    I can exceed the thermal and/or mechanical limits of a speaker and watch it fail in short order.

    These are electrical and physical truths and anything else is a myth.

     



    [edited by: Sparky3489 at 7:53 PM (GMT -5) on Mon, Mar 19 2012]

     Level II Electronics Technician, Certified IPC specialist in J-STD-001 and IPC-7711 \ IPC-7721, Peavey Media-Matrix NION technology certified

  • So what ? You just want to get on a forum and start an argument ? Lame.

    GLH Geeked

  • No argument to it. 

    I'm just dispelling the myths.

    The worst kind of information is wrong information and wrong information is lame.

     Level II Electronics Technician, Certified IPC specialist in J-STD-001 and IPC-7711 \ IPC-7721, Peavey Media-Matrix NION technology certified

  • http://community.crutchfield.com/forums/p/6169/35721.aspx#35721

    There is not much to argue here as all the comments are true.  It's the same thing we've said in the above thread and covered in the linked audiojunkies article.

    Sparky3489 saw a post out-of-context that was not worded as clearly as it could have been and commented there and made a general post to call attention to the issue.

    I'm fine with that.

    Anyone else have suggestions?

    2002 Ford Focus JVC KD-A815 Sony CDX-GT410u Sony XT-100HD HD Tuner Stock speakers, no amp, no subs

  • Sparky3489
    If you could blow subs by underpowering them, there would be no subs in existence since simply turning the volume down IS underpowering them.

    Turning down the power reduces the amplitude, but it doesn't alter the waveform in any other way. Clipping does alter the waveform in a very significant way. When lay people say "underpowering", they mean using an underpowered amp and turning it up until it clips, not simply turning down the gain. That seems obvious to me, but maybe not.

    Sparky3489
    As the signal simply "cuts" or "clips" at the maximum capacity of the amplifier, the signal is said to be "clipped." The extra signal which is beyond the capability of the amplifier is simply cut off, resulting in a fixed signal.

    You are incorrect. See below.

    Sparky3489
    I can drive speakers with a 100% clipped square wave signal all day long with no problems as long as the thermal and mechanical limits of the speaker are not exceeded.

    That's a pretty big "if" (as in "If the Queen had b*ll's, she'd be King). I can drive my car above red line all day as long as the engine doesn't overheat.  As TigerHeli's link explains, a clipped signal will produce more heat than a than an unclipped sine wave, so a clipped signal or a square wave is more likely to cause a thermal failure in a linear motor than a sine wave of the same amplitude. There is more heat being produced, and the motion of the speaker (which cools the voice coil) is reduced.

     If the speaker is designed to stay cool under those conditions (if the heat being generated does not exceed the limitations of the motor), then the speaker will not be damaged. If that is not the case, the build up of heat will damage the speaker. In any case, more heat is generated by a clipped signal than by an unclipped signal of the same amplitude. The closer the signal gets to being a square wave, the greater the amount of heat, and the less heat dissipation. The more heat builds up, the greater the chance of thermal failure.

    Sparky3489
    I can exceed the thermal and/or mechanical limits of a speaker and watch it fail in short order.

    See above.

    Sparky3489
    These are electrical and physical truths and anything else is a myth.

    Congratulations! That awareness is the first step toward a true understanding of the wonderful world of electronics. As a next step you may want to expand your understanding by picking up a textbook. When I was teaching, we used Electronic Devices, by Thomas Floyd for our first term students. It is chock full of all manner or truth (truth about electronics, truth about physics and geometry as they relate to electronics, truth about all sorts of stuff) and nary a myth to be found anywhere. I'm sure you would benefit tremendously from reading it. You may even be inspired to take a class or two.

     



    [edited by: Alex W at 12:54 PM (GMT -5) on Tue, Mar 20 2012]

         RESIma

  • As I understand it, we're all saying the same thing, but I might be missing some of the subtleties.  (Wouldn't be the first time!!)

    2002 Ford Focus JVC KD-A815 Sony CDX-GT410u Sony XT-100HD HD Tuner Stock speakers, no amp, no subs

  • Not exactly. I'm saying that an "underpowered" amp (i.e. one that does not have quite enough power for the task at hand) is likely to clip if driven too hard. I'm also saying that a clipped signal contains more energy than a "clean" signal of the same frequency and amplitude. I'm also saying that there is less movement of the motor with a clipped signal and therefore less cooling, so heat builds up more quickly.

    So if an "underpowered" amplifier is analogous to an underpowered automobile, then the clipped signal from an underpowered amp is more likely to damage a speaker than a clean signal of the same amplitude and frequency. Calculate the area within one cycle of a sine wave and a square wave and this should be obvious. Also consider that the driver is not moving (much) at the squared part of the clipped wave.

    The gist of it is that turning down the volume to limit amplitude is in no way analogous to a signal in which the amplitude is limited by clipping. To suggest that they are the same thing and that the resultant signal waveform will have the same effect on a speaker is dead wrong.



    [edited by: Alex W at 7:24 PM (GMT -5) on Tue, Mar 20 2012]

         RESIma

  • some brilliant guys on this forum.

    i'm with Tiger, i'm not sure there's really an argument here and seems like everyone is in full agreement.  i'm also with AlexW, since he seems to have ironed out the specifics the most succinctly and correctly (i'm really tired of saying that).  dampen you, Waverly!

    here's my take (and i don't have an electronics degree like some others, so probably simplistic, but it's a common sub issue so i HAVE TO jump in) :  clipping makes the average power exponentially higher, so a 100 watt amp will produce far more heat within the sub itself than a 200 watt amp will average when both amps are asked to produce 200 watts.  that FLAT or CLIPPED part of the signal is pure heat to a sub... the sub isn't provoked to move whilst in the 'clipped' portion of the cycle aside from it's own momentum.  during this part of the cycle, the sub receives a DC signal, which is the definition of 'clipping' or 'square wave.'  ...not the case when simply lowering the volume or turning down a gain. 

    this has been addressed very well already, and i believe most MODS are already aware of the difference between "underpowered" and "clipped signal," so just chipping in my 2 cents.  

    it's a nice post by the OP, however, and others may benefit.  this is the kind of thing where "stickies" would help, cuz everything Sparky said has already been said time and time again, but it keeps coming up.  i'd like to see a couple stickies for each sub-category.  maybe other MODS could preview it and offer approval?  we need sticky posts in some form, tho.

     

  • Alex W

    Not exactly. I'm saying that an "underpowered" amp (i.e. one that does not have quite enough power for the task at hand) is likely to clip if driven too hard. 

    Yes, "driven too hard" implies OVERPOWERING!!!!

    In a technical world and in a technical discussion, you have to be careful HOW definitions are thrown about.

    Alex W

    I'm also saying that a clipped signal contains more energy than a "clean" signal of the same frequency and amplitude. I'm also saying that there is less movement of the motor with a clipped signal and therefor less cooling, so heat builds up more quickly.

    Covered that here, "I can drive speakers with a 100% clipped square wave signal all day long with no problems as long as the thermal and mechanical limits of the speaker are not exceeded." What you fail to understand is if I were to feed a speaker a clipped signal well below it's tolerances of heat or mechanical stress, nothing will happen except horrible noise.

    Alex W

    So if an "underpowered" amplifier is analogous to an underpowered automobile, then the clipped signal from an underpowered amp is more likely to damage a speaker than a clean signal of the same amplitude and frequency.

    You left off the part about the automobile going uphill....to make it analogous.

    NONE of my statements are false, you just can't grasp the truth.

    Alex W

    Congratulations!

    Level II Electronics Technician, Certified IPC specialist in J-STD-001 and IPC-7711 \ IPC-7721 Industry standard

    I currently work in a facility that manufactures circuit boards for the Military DOD, Boeing, Raytheon, Midwest Microwave, Caterpillar and many other prestigious companies. I am head of the RMA department  and I perform all of the repairs on all boards that come in from the field. I can do circles around you all day, everyday, with the work I do.

    Congratulations! on being a member of a club.

    Oh, we hired a college professor once. He lasted two weeks. Those who teach....

     

     

     Level II Electronics Technician, Certified IPC specialist in J-STD-001 and IPC-7711 \ IPC-7721, Peavey Media-Matrix NION technology certified

  • Sparky3489

    Yes, "driven too hard" implies OVERPOWERING!!!!

    In a technical world and in a technical discussion, you have to be careful HOW definitions are thrown about.

    i'm not the best with these definitions, but i've always considered 'overpowering' to mean more power than the RMS rating, and nothing to do with clipping. 

    Sparky3489

    Alex W

    Sparky3489
    I currently work in a facility that manufactures circuit boards for the Military DOD, Boeing, Raytheon, Midwest Microwave, Caterpillar and many other prestigious companies. I am head of the RMA department  and I perform all of the repairs on all boards that come in from the field. I can do circles around you all day, everyday, with the work I do.

     

    I'm also saying that a clipped signal contains more energy than a "clean" signal of the same frequency and amplitude. I'm also saying that there is less movement of the motor with a clipped signal and therefor less cooling, so heat builds up more quickly.

    Covered that here, "I can drive speakers with a 100% clipped square wave signal all day long with no problems as long as the thermal and mechanical limits of the speaker are not exceeded." What you fail to understand is if I were to feed a speaker a clipped signal well below it's tolerances of heat or mechanical stress, nothing will happen except horrible noise.

    Sparky3489
    I currently work in a facility that manufactures circuit boards for the Military DOD, Boeing, Raytheon, Midwest Microwave, Caterpillar and many other prestigious companies. I am head of the RMA department  and I perform all of the repairs on all boards that come in from the field. I can do circles around you all day, everyday, with the work I do.

    hmm, now you're getting personal.  flaming is bad, but perhaps your advice carries some weight (i believe it does, bcuz i've stated similar things myself), but going on the attack against another user who also offers good info without a sense of humility is frowned upon in this community.  try to be less insulting in the future.  i really doubt AlexW needs anyone to defend him, but i'd also like to advise him that flaming is discouraged before he goes off... this forum is not about resolving personal differences.

     

  • Sparky3489

    Yes, "driven too hard" implies OVERPOWERING!!!!

    No, it doesn't. The amp is underpowered if it cannot deliver adequate voltage to the load. "Driven too hard" simply means that the amp is being asked to deliver what it cannot cleanly deliver (driven beyond its limits would be another way of putting it). Overpowering means something quite different, by the way. It doesn't typically relate to electronics. I suppose it could be that the stench from a smoked speaker would be overpowering. Possibly it was damaged by an underpowered amplifier. Who's to say?

    Sparky3489
    You left off the part about the automobile going uphill....to make it analogous.

    Going up hill, towing a boat, fat kids in the back seat, or just not up to the task. All the same.

    Sparky3489
    NONE of my statements are false, you just can't grasp the truth.

    Yes, "driven too hard" implies OVERPOWERING!!!!

    FALSE. See above.

    If you could blow subs by underpowering them, there would be no subs in existence since simply turning the volume down IS underpowering them.

    FALSE. An amplifier that is driven into clipping because it lacks sufficient power (it is underpowered, let's be careful about how terms are thrown about. This is a technical discussion.) produces an entirely different waveform than an amplifier with sufficient power producing a signal of the same amplitude same amplitude. The clipped signal is more likely to cause damage to a driver.

    Clipping is one form of distortion...

    FALSE. Distortion is a result of clipping. Again, let's be careful about how terms are thrown about. This is a technical discussion!

    Sparky3489
    Level II Electronics Technician, Certified IPC specialist in J-STD-001 and IPC-7711 \ IPC-7721 Industry standard. I currently work in a facility that manufactures circuit boards for the Military DOD, Boeing, Raytheon, Midwest Microwave, Caterpillar and many other prestigious companies. I am head of the RMA department  and I perform all of the repairs on all boards that come in from the field. I can do circles around you all day, everyday, with the work I do.

    I'm very familiar with your certifications. I'm sure your soldering skills are excellent. Not relevant to this topic, but excellent nonetheless.

    Sparky3489
    Oh, we hired a college professor once. He lasted two weeks. Those who teach....

    Maybe he had moral qualms (never trust a liberal elitist intellectual academic when there are homes to be bulldozed and people to be incinerated). I sold my shares in Caterpillar for the same reason (I did wait until the stock split, however).

    Besides, I taught a post-secondary electronic engineering technology degree program. In other words, I taught people like you to do what you do (and a bit more, it seems). Prior to that, I spent 25 years in the field of consumer electronics.

    I think GLH was right.

     

         RESIma

  • @J Ro - I thought mods could sticky threads, but I think only admins can.  There are two problems though: First - as this thread is a perfect example - what starts as a perfectly useful and helpful info degrades in personal attacks and arguments over minutia and pretty soon someone mentions cheese danish's and the thread isn't worth reading anymore.  Second - I've seen forums where you have 15 sticky posts at the top of each forum and you have to scroll down to get to the new posts.  That can be avoided by having a sticky "Read this first" thread with links to the other 15 threads, but then nobody does that and it defeats the purpose.

    Back on-topic - I'll give my definition of some terms, probably NOT the dictionary definition - but hopefully something we can agree on (and close to what Sparky said, but not identical).

    Underpowered - Literally, simply supplying less power to a sub than it is designed for.  i.e. using a 200W RMS amp with the gain set to limit the output to 200W RMS to power a 500W RMS subwoofer.  Should cause no damage to the sub - assuming the sub is properly rated to begin with and the amp can make a "clean" 200W RMS.  The subwoofer would sound better with more power, though.

    There isn't really a proper term for it, but using a 750W RMS amp with a 500W RMS sub and keeping the volume at 20% so the amp only produced 250W RMS would also be considered underpowering.

    Overpowered - As J Ro said - literally using a 750W RMS amp set for 750W RMS with a 500W RMS sub.  The sub MIGHT be damaged, but it is going to depend on how long the sub is exposed to the higher voltage and failure is either from thermal or mechanical overload.

    Underpowered and overdriven - Usually referred to as "clipping" - basically hooking up a 200W RMS amp to a 500W sub and asking the amp to produce more than 200W to get the desired output from the subwoofer.  Produces a square wave and can easily damage the subwoofer.

     

    Finally - the way electronics are rated doesn't help either - there are 200W RMS amps that easily make 250 to 300W RMS and there are 200W amps that are lucky to make 50W RMS, and a 500W RMS sub will not be instantly damaged by seeing 501W RMS, etc.

    Hope This Helps!!!

    Anyone else have suggestions?



    [edited by: TigerHeli at 4:59 PM (GMT -5) on Wed, Mar 21 2012]

    2002 Ford Focus JVC KD-A815 Sony CDX-GT410u Sony XT-100HD HD Tuner Stock speakers, no amp, no subs

  • Sparky3489
    I currently work in a facility that manufactures circuit boards for the Military DOD, Boeing, Raytheon, Midwest Microwave, Caterpillar and many other prestigious companies.

    Alex W
    never trust a liberal elitist intellectual academic when there are homes to be bulldozed and people to be incinerated
    LOL!  i'm in stitches!!!



    [edited by: J Ro at 4:48 PM (GMT -5) on Wed, Mar 21 2012]
  • J Ro
    ]LOL!  i'm in stitches!!!

    He, he, he. I thought you might like that one.



    [edited by: Alex W at 7:12 PM (GMT -5) on Wed, Mar 21 2012]

         RESIma

  • was that snarky remark meant just for me?  aww...

    maybe no one else will get it, but that's my kind of comedy!  god i hate myself for laughing so hard... everytime i look at this post my roommate starts complaining about the noise!  fire good, but hilarity better!