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Too Little Power

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Forum Name: Car Audio - Hot Topics
Forum Discription: Stickied topics from our car audio forum. Car Audio FAQs. Read First!
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=74226
Printed Date: June 15, 2021 at 10:40 AM


Topic: Too Little Power

Posted By: Steven Kephart
Subject: Too Little Power
Date Posted: March 09, 2006 at 11:24 PM

Hey guys.

I'm having a debate at work on this topic.  I took a W7 in a sealed enclosure tonight and hooked it up to one of our small 250 watt Alpine amplifiers with the gain and bass boost all the way up and ran it for about half an hour.  It played just fine afterwards.  But for some reason they still don't believe me that too little power does not blow speakers.  I then showed them the information at bcae1.com.  I was hoping that someone here might have some good links to other reputable websites that also disprove this myth.  Thanks for any help!

ADDED BY MOD:  Link to great discussion on this topic from some respected industry experts, including people like Manville Smith of JL Audio, Mark Eldridge of JL Audio and multi IASCA world champion, and Andy Wehmeyer of Harman Kardon. :  https://www.audiogroupforum.com/csforum/showthread.php?t=4332&highlight=clipping+blown



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Replies:

Posted By: ophidia31
Date Posted: March 09, 2006 at 11:28 PM
the only way id see that too little power would blow a speaker is if you drive the amp into clipping and destroy the speaker fom distortion. other wise, if its still clean and un distorted then i dont see how you can blow a speaker. i mean, my sub would be blown ages ago since i doubt i have the amp turned up that much to run 750rms through the sub.

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Posted By: Steven Kephart
Date Posted: March 09, 2006 at 11:34 PM
Distortion won't make a difference either.  My above experiment proved this as the amplifier WAS fully clipped and distorting horribly.  Speakers are ALWAYS blown by too much power; period.  Here's a link to an earlier discussion on this: https://www.the12volt.com/installbay/forum_posts.asp?tid=69552&KW=dyohn+kephart&PN=0&tpn=2




Posted By: ophidia31
Date Posted: March 09, 2006 at 11:42 PM

boy, its late and i feel stupid. posted_image after i thought about it then yeah, id have to agree with you that youd have to overpower the speaker in order for it to blow. put me down for myth busted.



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Posted By: willdkartunes
Date Posted: March 10, 2006 at 3:12 AM

This is a very tricky question. With the situation you stated with the small Alpine amplifier, your right. You would smoke that amplifier faaaaar before that subwoofer would ever blow.

On the other hand, I have personally heard a subwoofer DAMAGED by running too little power to it and blasting the volume. Of course this equation all depends on two things:

1) The volume at which you play the "under-powered" subwoofer.

2) How "little" of power your actually applying to the subwoofer.

I once did a little experiment with a friend based on this underpowering theory. We hooked up a nice JL sub (don't worry it was free) to an old 60 watt Hifonics amplifier. We played the subwoofer the whole time in free air resonance to try to keep the results from being flawed by different enclosure sizes. I am by no means a scientist, but we did try our best to keep experimental errors to a minimum. We cranked the amplifier gain just as you stated with your test. At low volumes it sounded all right, but certainly nothing special. Lets just say that at low volume, it played....

We then began to slowly turn up the volume. The louder we got the volume, the worse it sounded... until we got the volume past 80%.... we then heard a loud popping sound from the woofer and immediately shut it off. We thought we had blown the subwoofer, but to our surprise after examination the subwoofer appeared to be intact. We played that same subwoofer later on hooked up to a 500 watt JBL amp and it still thumped! I do know for a fact that we definitely did damage to the speaker though, because it just didn't sound the same. It had a little internal rattling on certain frequencies and couldn't hit the low ones like it could before. (kinda sounded like the voicecoil was in the early stages of blowing) By the way, it was originally hooked up to the JBL amp and it sounded great... until I asked the question about putting a lot less watts on it. That's when the experiment begain and the subs "sound quality" got decreased. lol.

My friend also told me that a week later, the subwoofer blew. He didn't unhook it from the JBL amplifier and he claims that it didn't even blow at a high volume. He said he was just listening to some reggae beats and then say goodbye to the JL sub! I'm not going to say for sure that the sub blowing was a direct cause of our "experiment". There could have been other factors that played a part in the course of the week that caused the failing sub.

Is it possible to BLOW a sub with too little power? maybe.  With continued use at very low wattage and very high volumes, I would say it could be possible. Typically, no. Almost all subwoofers blow with too much power and not too little. As far as concrete, scientifical evidence goes, I don't know a site that states this too little power theory to be true,sorry. I do know what I saw and heard. Hope that helps.



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Do whatever makes you happy in life without diminishing the happiness of others




Posted By: gbear14275
Date Posted: March 10, 2006 at 4:16 AM

OK, One thing I did not see is any significant mention of heat.  This is the most prominent killer of subs that I know of.  Mechanical damage springing from the over stressing of the spider is another main source BUT...  I think the main point of BCAE explanation about clipping is that it prevents the speaker from cooling itself well enough. SO heres my take on this...

Driving a speaker with a clipped signal creates the opportunity to damage the speaker.  This depends on the speaker and how much power is used.  The first thing we need to establish is that a speaker(voice coil) makes heat.  I was going to go into great detail here but decided not to.  (it was getting to be quite the work of art though :)).  This is the enemy we face when we talk about underpowered amplifiers and clipping.

If we can agree that a voice coil makes heat then we should also agree that it needs to disapate this heat otherwise bad things are going to happen.  When a speaker moves, it moves air; not unlike a fan moves air.  When a speaker moves correctly it moves alot of air and so cools itself very well (hopefully if its designed well).  When a speaker moves with a clipped signal it is like only moving a fan in little burts (Swing left...Stop...swing right...Stop...etc.).  Beacuse of this the speaker is not cooling itself as the designers made it to.  All the while however, curent is still flowing through the voice coil (FULL power when its stalled at the top or bottom of a clipped signal) and this current is constantly making heat and leading to disaster (the cooling offsets this with equal magnitude normally).  So what ends up happening is you have a speaker not cooling itself and having lots of current flowing through it (the ratio of cooling to power gets worse as the clipping approaches a square wave). 

SO depending on the heat tolerances of the speaker and how it was designed a underpowered amplifier could very easily cause speaker damage.  This will usually be by melting the insulating substance that keeps the coils from shorting out...thereby letting them short out...which only makes a huge drop in the resistance of the speaker...which means more current and more heat only now extremely localized...and eventually all this usually leads to the voice coil itself breaking because its now been turned into a fuse. 

But many speakers these days use quality materials in the construction of these key areas and speaker manufacturers are over building their subs.  What this means is that even with less than optimal cooling the speakers voice coils and insulating substance have heat tolerances that the conductive and radiating cooling is enough to keep any problems from arising for most amps rated under the speakers ratings.

Now you are completely right that a larger amplifier will manifest this problem much more quickly and putting more power through a speaker than it was designed for will obviously overload the designed cooling capacity.  But if your doing that your probably over loading your spider as well and other problems such as the former coming off the pole or destroying its voice coil through hard bottoms.

So still confident that its not going to happen?  I'll show you!  Set up the same speaker and amp but now instead of turning the gains up to produce clipping, I will just give you a clipped audio signal.  (why?  because many amplifiers these days have circutry in them that most likely limits clipping and so most amplifiers will not go into extreme clipping.  BUT...hehe... We are looking to prove your point that no amplifier putting out less power than a speaker is rated for can blow the speaker.)

So if your man enough to back your talk up with aciton...burn this to a CD (its just an audio file like any other song only extremely repetative) and put that speaker amp combo back on for another hour..If you can :).

6.25Hz Clipped Signal (MP3 Format): https://h1.ripway.com/gbear14275/6.25Hz_Clipped.mp3 (songs under 13 min, if you can play it for that long...)

(The W7 model has some advanced cooling technologies incoporated into it and so it might be fine...But if you do this I would be prepared to buy the speaker...and possibly the amp for some reason if its protection circuts fail.  Also this is an extremely low frequency mp3 file, make sure the amp you use does not have a subsonic filter on it.)



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Posted By: Steven Kephart
Date Posted: March 10, 2006 at 4:23 AM

Hey guys, I think you misunderstood the purpose of this thread.  I wasn't trying to learn whether it is possible or not because I know for a fact that it isn't possible.  In every way, shape and form if a subwoofer was blown, it was due to too much power.  Even in your above example, you damaged that sub by too much power.  You pushed the sub past it's mechanical power handling which caused damage.  Keep in mind that mechanical power handling is a function of the enclosure, or in your case the lack of it. posted_image

The point of this thread was to gather some more reputable web links which I could use.  So, does anyone have any?





Posted By: Steven Kephart
Date Posted: March 10, 2006 at 4:47 AM
gbear14275 wrote:

If we can agree that a voice coil makes heat then we should also agree that it needs to disapate this heat otherwise bad things are going to happen.  When a speaker moves, it moves air; not unlike a fan moves air.  When a speaker moves correctly it moves alot of air and so cools itself very well (hopefully if its designed well).  When a speaker moves with a clipped signal it is like only moving a fan in little burts (Swing left...Stop...swing right...Stop...etc.).  Beacuse of this the speaker is not cooling itself as the designers made it to.  All the while however, curent is still flowing through the voice coil (FULL power when its stalled at the top or bottom of a clipped signal) and this current is constantly making heat and leading to disaster (the cooling offsets this with equal magnitude normally).  So what ends up happening is you have a speaker not cooling itself and having lots of current flowing through it (the ratio of cooling to power gets worse as the clipping approaches a square wave). 


I think you would be surprised at how insignificant this is.  For one thing, the reduced cone motion you describe isn't as significant as you would expect.  But here's a great white paper about dual voice coil drivers that will show you how insignificant it is: https://www.adireaudio.com/Files/TechPapers/DualVoiceCoilDrivers.pdf

gbear14275 wrote:

SO depending on the heat tolerances of the speaker and how it was designed a underpowered amplifier could very easily cause speaker damage.  This will usually be by melting the insulating substance that keeps the coils from shorting out...thereby letting them short out...which only makes a huge drop in the resistance of the speaker...which means more current and more heat only now extremely localized...and eventually all this usually leads to the voice coil itself breaking because its now been turned into a fuse. 

So how is that "underpowered"?  There is obviously too much heat causing the melting you describe, which means too much power.

gbear14275 wrote:

Now you are completely right that a larger amplifier will manifest this problem much more quickly and putting more power through a speaker than it was designed for will obviously overload the designed cooling capacity.  But if your doing that your probably over loading your spider as well and other problems such as the former coming off the pole or destroying its voice coil through hard bottoms.

And that's exceeding the mechanical power handling of the driver.  But you are still causing damage from too much power.

gbear14275 wrote:

  So still confident that its not going to happen?  I'll show you!  Set up the same speaker and amp but now instead of turning the gains up to produce clipping, I will just give you a clipped audio signal.  (why?  because many amplifiers these days have circutry in them that most likely limits clipping and so most amplifiers will not go into extreme clipping.  BUT...hehe... We are looking to prove your point that no amplifier putting out less power than a speaker is rated for can blow the speaker.)

So if your man enough to back your talk up with aciton...burn this to a CD (its just an audio file like any other song only extremely repetative) and put that speaker amp combo back on for another hour..If you can :).

6.25Hz Clipped Signal (MP3 Format): https://h1.ripway.com/gbear14275/6.25Hz_Clipped.mp3 (songs under 13 min, if you can play it for that long...)

(The W7 model has some advanced cooling technologies incoporated into it and so it might be fine...But if you do this I would be prepared to buy the speaker...and possibly the amp for some reason if its protection circuts fail.  Also this is an extremely low frequency mp3 file, make sure the amp you use does not have a subsonic filter on it.)

BTW... I wont consider you less of a man if you back out now.  In fact the saying goes it takes the bigger man to admit when he's wrong.


When did I say anything about "rated" power?  I am saying that damage to speakers is caused by too much power every time, independant of the rating the manufacturers marketing department decided to slap on the sub.  If you heard what the subwoofer at work was producing, it would be very obvious to you that the amplifier was clipped as the music was highly distorted.  But as Dyohn said in the link I provided above,

"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."





Posted By: DYohn
Date Posted: March 10, 2006 at 10:19 AM

Steven: tell your colleagues who doubt you to go back to school and study some physics.  Maybe some basic electricity would help too.  :)

And gbear, please read Steven's responses carefully.  He is 100% correct.

As far as other web sites, that should be unnecessary for anyone who understands the basics of how a loudspeaker works.  But I'll see if any manufacturers have posted information about this pervasive myth.



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Posted By: Alpine Guy
Date Posted: March 10, 2006 at 10:50 AM

I didn't really read the above posts, but i was thinking. Even if you were feeding a speaker less power than its rated for at a fully clipped signal, could it be possible for the power to jump across the windings and eventually just weld them so much that the VC windings actually melt and separate leaving a gap?

I can honestly say i don't know as much about the electrical aspect of the speakers as i should, i have 4 years of Electrical engineering in school ahead of me tho posted_image ..and i can't wait!



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2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.




Posted By: DYohn
Date Posted: March 10, 2006 at 11:48 AM

Alpine Guy wrote:

I didn't really read the above posts, but i was thinking. Even if you were feeding a speaker less power than its rated for at a fully clipped signal, could it be possible for the power to jump across the windings and eventually just weld them so much that the VC windings actually melt and separate leaving a gap?

No, this can't happen as long as the power rating of the voice coil is not exceeded.  What you are describing might happen if too high a voltage was presented to the coil.  The insulation on the coil windings are rated for a particular maximum voltage (as is the insulation of any wire) and if it is grossly exceeded you might be able to arc-over (or flash) the windings.

The way clipping can damage a loudspeaker is if the available amplifier power is already at or over the coil's thermal limits when the signal gets clipped.  A clipped signal presents an increase in power over an AC signal by as much as 100%- and sometimes more.  If an amplifier is producing say 100 watts of music signal, in full clip mode this will jump up to as much as 200 watts (or depending on the available rail voltage, even more.)  So if your speaker is only rated for a thermal load of 100 watts, the clipping amplifier will overload it and potentially fry it. 

This is the origin of the "under-power myth."  If your speakers are rated for 150 watts and you use a 100 watt amplifier then drive it into full clipping, it is actually delivering more like 200 watts of effective power to the speaker when the speaker blows.  "Oh," you say, "I used a smaller amplifier than the speaker rating and it blew.  Therefore under-powering must blow speakers."  No, what happened was idiotic amplifier setup blew the speaker.  If on the other hand you are using a speaker rated for 500 watts and run the same full-clipped signal from the 100 watt amp, it will hum along all day producing horribly distorted clipped sound, but it will not care since you are not exceeding it's power capacity.  Did that make sense?

Also, a clipped signal is in effect a momentary DC signal.   A DC signal will make the loudspeaker motor stop moving.  Movement of the voice coil is what cools it.  The heat generated by a DC signal may be enough to overheat the coil windings if you again are using an amplifier that can exceed the power capacity of the speaker, it is possible to overheat the speaker due to loss of cooling.  I believe this is what gbear was getting at.   But the amp must be operating over the power limits of the speaker and the clipping must be severe or the speaker will not care.

It's a complex problem, actually.  Many people will recommend that you always use larger amplifiers than a speaker's ratings in order to stay away from the clipping threshold (this is called amplifier headroom.)  This is good advise IF and only if you understand how to ensure you never overpower the speaker.  Fuses or gain adjustments can help in this, but ultimately it is all about monitoring the power levels and paying attention to not exceeding them.  Not commonly done in car audio.  The other recommendation is to always use speakers rated to handle at least 3X the power output of your amplifiers (speaker headroom.)  This way, even if you do clip the signal now and then, the speaker can handle it.  But again, in car audio most customers feel they are somehow being "cheated" if they cannot use "the full potential" of their system - whatever that is.  So, the compromise, and what I usually recommend, is to use amplifiers that do not exceed the average power handling capability of the speakers, and then carefully set the gain so the amplifier will not clip under normal usage.  Then be careful with the volume knob and don't "crank it."

If under any circumstances a user finds themselves "cranking it" too much, or wanting to turn up gains to try and squeeze more out of a system, then they need to purchase a new system, plain and simple, or they will fry what they have in short order.  posted_image



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Posted By: Alpine Guy
Date Posted: March 10, 2006 at 12:08 PM
This thread should be added to the long sticky list, its very informative.

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2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.




Posted By: Steven Kephart
Date Posted: March 10, 2006 at 1:21 PM
DYohn] wrote:

P>Also, a clipped signal is in effect a momentary DC signal.   A DC signal will make the loudspeaker motor stop moving.  Movement of the voice coil is what cools it.  The heat generated by a DC signal may be enough to overheat the coil windings if you again are using an amplifier that can exceed the power capacity of the speaker, it is possible to overheat the speaker due to loss of cooling.  I believe this is what gbear was getting at.   But the amp must be operating over the power limits of the speaker and the clipping must be severe or the speaker will not care.


This is something I have been curious about.  When I've set gains on amplifiers in the past using an Osciloscope; at the point when I meet and then exceed the point of clipping, the wave form doesn't just cut off the top flat like you would expect.  What instead happens is the peak inverses on itself.  This seems to show that the signal doesn't hold the cone in place, but in fact still keeps it moving.  This makes sense based on how Dan has always described a subwoofer as being a constant acceleration device.  So whether it is accelerating or decelerating, it is constantly in motion as long as there is some form of signal on the driver.  And that is why I believe the "loss of cooling" is rather insignificant.  Or am I understanding this wrong?  I will admit that this is something I haven't fully studied.





Posted By: Steven Kephart
Date Posted: March 10, 2006 at 1:25 PM
DYohn] wrote:

P>As far as other web sites, that should be unnecessary for anyone who understands the basics of how a loudspeaker works.  But I'll see if any manufacturers have posted information about this pervasive myth.


Thanks!  I actually tried to do a google search on this, and was rather shocked at how many topics I came upon that perpetuate this myth.  But I figured some of you guys may have ran into something in the past that might help.





Posted By: DYohn
Date Posted: March 10, 2006 at 1:45 PM

Steven Kephart wrote:

This is something I have been curious about.  When I've set gains on amplifiers in the past using an Osciloscope; at the point when I meet and then exceed the point of clipping, the wave form doesn't just cut off the top flat like you would expect.  What instead happens is the peak inverses on itself.  This seems to show that the signal doesn't hold the cone in place, but in fact still keeps it moving.  This makes sense based on how Dan has always described a subwoofer as being a constant acceleration device.  So whether it is accelerating or decelerating, it is constantly in motion as long as there is some form of signal on the driver.  And that is why I believe the "loss of cooling" is rather insignificant.  Or am I understanding this wrong?  I will admit that this is something I haven't fully studied.

No, actually you are right on.  Many other effects such as inductive or capacitive discharges will impact the signal as soon as it approaches DC and cause the waveform to continue changing.  The only time the loss of cooling effect becomes significant is in a hard clipped square-wave at a very low frequency, and even then the signal would try to instantaneously accelerate the voice coil from full positive to full negative deflection, which of course cannot happen.  There is also the effects of power compression which will blow a speaker and are often masked by clipping.  The reason I mention it as a contributing factor is because of cumulative effects over time (meaning the longer the signal is in clipping condition the more heat can build up inside the motor assembly.)  A clipped signal can and does cause the woofer motion to "stop," even if it is only a micro-stop.



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Posted By: gbear14275
Date Posted: March 10, 2006 at 11:56 PM

Steven Kephart wrote:

When did I say anything about "rated" power?  I am saying that damage to speakers is caused by too much power every time, independant of the rating the manufacturers marketing department decided to slap on the sub.  If you heard what the subwoofer at work was producing, it would be very obvious to you that the amplifier was clipped as the music was highly distorted.  But as Dyohn said in the link I provided above,

"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."


Ok if this is what you mean then your argument and answers are trivial.  It's like you claim all car accidents are the result of excessive speed and then when someone disagrees you reply.  If the car crashes rolling around at 1 MPH and runs into a garbage can that 1MPH is what caused it to run into the garbage can and so the 1MPH was excessive speed.  Technically your right because without the movement the there would be no accident but you see there really is no value in arguing in this technical manner.

You obviously understand the technicalities of speakers and power but for those who do not have the knowledge or don't think in that manner you are probably conveying to them that under rated power cannot blow speakers.  Which is obviously untrue.

So yeah we were both right and both wrong depending on our definitions of the problem.  I think what the best course of action would be though is for both of us to explain the matter as if we were talking about whether or not an amp rated as putting out less power than a speaker is rated for can cause damage.  Of which the answer is yes.

I understand what your saying and therefore know that you are in fact 100% correct but we should help the less educated...and argue about problems that are less easily solved.  That should be way more fun :)

But good debate even if we were arguing the same point at one another! (I hate when that happens lol) :) :)





Posted By: willdkartunes
Date Posted: March 11, 2006 at 12:22 AM

Steven Kephart,

Were you saying that the speaker damage was due to the subwoofer not being in an enclosure? Wouldn't I have to drastically change the enclosure size when going from 500 watts down to 60 watts?

By the way, I ran the same experiment with the same amplifier and same type of subwoofer. I obviously couldn't use the exact same subwoofer since  I mentioned earlier it is already dead. So I just used the same exact model and brand - JL 10w7. With the same 60 watt amplifier I didn't turn the amplifier gain to full, but instead left it half-way. I got an identical result of what I described in the first experiment. It just took a little longer for the "damage" to occur.

Of course if the reasons for the speaker damage were due to having the subwoofer in no enclosure then the experiment is indeed flawed...

I know your original thread had stated for another website to provide more information on this topic. I'm really sorry about not being able to produce a website so you could read someone elses findings. I figured that maybe my experience with this topic could possibly be of some help. Or maybe I was wrong....



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Do whatever makes you happy in life without diminishing the happiness of others




Posted By: stevdart
Date Posted: March 11, 2006 at 12:23 AM

gbear] wrote:

ou are probably conveying to them that under rated power cannot blow speakers.

That's an odd inference.  I didn't understand him to say that at all.  Even we uneducated and technically illiterate  understand that power is power, regardless of a manufacturer's rating.

posted_image

Sometimes subjects like this need to be beat around a bit.  There's always a few more of us who "get it" each time.



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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.




Posted By: Steven Kephart
Date Posted: March 11, 2006 at 1:19 AM
gbear14275 wrote:

Ok if this is what you mean then your argument and answers are trivial.  It's like you claim all car accidents are the result of excessive speed and then when someone disagrees you reply.  If the car crashes rolling around at 1 MPH and runs into a garbage can that 1MPH is what caused it to run into the garbage can and so the 1MPH was excessive speed.  Technically your right because without the movement the there would be no accident but you see there really is no value in arguing in this technical manner.


Not at all.  In your example, there are possibilities of outside sources that could cause the results (turning of the wheel, etc.).However in a subwoofer system as I describe, there isn't any extrenal source causing the damage.  It is the excess power causing the voice coil to thermally open, or drive the cone beyond it's mechanical limits.  And if the power available is lower than what it takes to cause those situations, then there won't be any damage, no matter how distorted, clipped, or low the power levels are.  Claiming that "underpowering" causes the damage would suggest otherwise, and is propogating a myth.  Instead of lying to someone, wouldn't it be better to explain the truth, or at least say be careful or they could cause damage?

Also, in your example it wasn't the speed that caused the damage to the vehicle, but excessive force (Force=Mass*Acceleration).  So to keep the analogy going, would you claim that too little force is what caused the damage to the vehicle?  posted_image





Posted By: gbear14275
Date Posted: March 11, 2006 at 3:08 AM

*sigh* OK...So your arguing if dmage happens to the speaker then there is too much power otherwise nothing will happen?  Your argument seems circular.  The fact of the matter is you have to redefine your terms.  The myth is propogated using an amps rated output and a speakers rated power handling.  By redefining your definition of power your not keeping the myth from propogating, instead your just trying to prove a truth: 

*If a speaker is damaged because its (pick one: thermal, mechanical, etc. ) power limits were exceeded, there was too much power.

This really is basically what your saying.  And I think you know your being difficult. 

If you define your terms according to the myth then your argument is not longer true. 

If you want to get technical geek style *pushes glasses up* then here is a techincal example of an underpowered speaker being damaged.

Speaker A is powered by Amplifier B whos power ratings in no way exceed the capabilities of the sub.  The amplifier recieves a signal and energizes the voicecoil (some steps may be skipped).  Magnetic field is created, forces begin to cause the speaker assemply to move.  and the underpowered amp causes the speaker to travel into a screwdriver tip which has been positioned within the comes limits of travel. OR The gap has been contaminated by grains of sand which preceed to eat away at the former and voicecoil until it causes failure. OR current starts to flow through the speaker terminals which happen to be wired in parrallel to a current detecting detonaiton device which explodes thereby rendering the speaker useless.

You never said that the speaker had to be in a suitable envronment. 

Or heres a more realistic one:  The speaker has a manufacture defect that makes the former detach from the cone and spider.  Underpowering strikes again.

Basically what I am saying is play fair.  You know the common understandings of the myth and your insistence on redefining ratings, power, and limits is not helping the situation.  A good sticky would be an explanation of how "underpowering" as it is commonly referred to can actually be "too much" power in a clipped signal situation to cause speaker failure.  That way something constructive actually comes from this thread.





Posted By: willdkartunes
Date Posted: March 11, 2006 at 4:56 AM

This thread's posts have been getting absolutely facinating and quite interesting to read, but I still have no idea why nobody will even consider what I was saying...

Try it out for yourself! Use whatever sub you want and put the smallest amplifier that you can come across on the sub of your choice. (less than 80 watts for a high rms sub, and less than 50 watts for a low rms sub) You don't even have to turn up the amplifier gain if you don't want to, and you can put the subwoofer in an enclosure too. I guarantee you will come up with the same results that I did. The subwoofer will eventually be damaged if not blown with extended use at a high volume. (over 80%) By "extended" I mean 40 or more minutes of playing time. It doesn't even have to be consecutive minutes either. 5 or 10 minutes here and there.... It will eventually be damaged though! If you don't crank the volume and keep it at a reasonable level, then guess what? The subwoofer will just sound like crap. ONLY if the volume is high will the subwoofer be damaged, if not you will only hear a terrible sounding subwoofer.

That pretty much answers steven kephart's original arguement of will a subwoofer blow being underpowered. It could.... but chances are no. Depends on the volume.

Anyone reading can try it and you'll see for yourself. Keep the volume low and the subwoofer is fine. Crank the volume up and the subwoofer could possibly be damaged or blown. It's as simple as that.



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Do whatever makes you happy in life without diminishing the happiness of others




Posted By: stevdart
Date Posted: March 11, 2006 at 9:41 AM

wildkartunes wrote:

We played the subwoofer the whole time in free air resonance to try to keep the results from being flawed by different enclosure sizes.

The problem is, your experiment was just an observation, not a controlled test.  It's very easy to exceed the voice coil travel with uncontrolled input in an uncontrolled free air environment.  You might look into the large sealed chamber-type environments that are used by manufacturers to control the damping of the driver.  You would have to set up precise controls in every aspect of this experiment in order to arrive at some sort of a conclusion.



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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.




Posted By: kirktcashalini
Date Posted: March 11, 2006 at 10:31 AM
its impossible to blow a speaker from underpowering. just think of it as playing it at quarter volume... hey wildkartunes, if you want to run tests on a 10w7, send it to me before you break it, I'll send it back in a year or two, thennn you can rip it apart.

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Posted By: DYohn
Date Posted: March 11, 2006 at 11:26 AM

willdkartunes, I don't follow your "experiment."  Please describe what you did with a 60 watt amplifier and what "damage" you observed.

gbear, no one is redefining anything that I can see and your examples about outside influences (screwdriver tips?) are moot and I do not believe are at all what I or Steven are discussing.  Short of some sort of mechanical damage or manufacturing defect, the only thing that damages loudspeaker voice coils is heat.  The only thing that causes heat is power dissipation.  The only way sufficient heat can be built up to exceed the voice coil's ratings is by attempting to dissipate more heat energy than the motor system can handle.  The only way there can be excessive heat is through too much input power, OR if the heat dissipation ability of the motor assembly is compromised such as the loudspeaker is reaching Xmech, or in some cases (especially in speakers with small Xmax values) by heat build-up over time due to input signal clipping.

I used to work in a lab where one of our main functions was testing loudspeakers (and other audio and video gear.)  I have personally placed a loudspeaker in a  free-air test clamp on a square wave signal (simulating a 100% clipped signal) for extended periods of time and measured the heat build-up and can tell you with certainty that as long as the thermal and mechanical limits of the speaker are not exceeded (i.e.: as long as the power input is low enough to not deliver too much energy into the VC) the speaker will play that square wave indefinitely with no damage at all.  Turn up the power, and poof goes the VC.

Please read my comments made earlier concerning my belief for the origin of the "underpower" myth.  It actually has nothing to do with underpower, it has to do with overpower in all cases that I have ever seen scientifically discussed or illustrated.

Cheers



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Posted By: Steven Kephart
Date Posted: March 11, 2006 at 12:18 PM
gbear14275 wrote:

A good sticky would be an explanation of how "underpowering" as it is commonly referred to can actually be "too much" power in a clipped signal situation to cause speaker failure. 


Read this link provided in the original thread: https://www.bcae1.com/2ltlpwr.htm

gbear14275 wrote:

That way something constructive actually comes from this thread.


This thread was never intended to be a discussion on this topic as we have already discussed it.  Instead it was supposed to be a way for me to obtain more technical websites to use as support. 





Posted By: gbear14275
Date Posted: March 11, 2006 at 12:35 PM

Dyohn,

I completely agree with both you and Stephen on the issue of too much power being the cause of damage (by the definition of too much this is self validating).  But the problem is that the myth doesn't talk about the difference between rated power given by an amplifier and the actual power being delivered in a clipped environment.  WE understand how a square wave actually produces more power than a sine wave because we are informed and understand some of the more detailed aspects of amplifier and speaker operation (I'm positive I don't know as much as you two but I think i still know more than most). 

If we think about the forum this statement is usually made in the understanding of the term "power" is the rated capabilities of the amplifier.  This is because many times it is someone who understands thermal limits and clipping etc. that does not want to sit down and educate MC Dudley cool guy who just walked off the street into the stereo shop and is going to turn his gains all the way up to make his stuff louder.  Instead of presenting a argument on the defnition of "too much" pawer, us arguing that if the power supplied makes the voice coils melt it's too much becaus its exceeded the thermal limits of the speaker.  We should instead (and maybe a sticky would be really great on this topic) try to spread the understanding of how speaker damage occurs especially when clipping gets involved.  A sticky on clipping and its effects...now dyohn THAT would be a GREAT sitcky!!!





Posted By: DYohn
Date Posted: March 11, 2006 at 12:54 PM

Isn't that what I said in my answer to Alpine guy?  It has nothing to do with the "rated" power on an amplifier, it has to do with actual effective output exceeding the speaker's limits.  So why the argumentative posts?  Or was I mis-reading you?



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Posted By: DYohn
Date Posted: March 11, 2006 at 1:18 PM

Steven, back to your original question.  Here are some resources.

This tech note from Monty Ross, an engineer and designer at Rane.  It discusses power compression in tweeters and is designed to sell one of their products, but the concepts may be helpful.

A nice technical article from Xtant on how they measure their loudspeakers and establish their ratings, with some good comments on loudspeaker failure modes.

An article focused on pro audio with good comparisons between AES, IEC and EIA test methods, and a few statements at the end concerning power effects on loudspeaker failure.

And lastly, here's a great article by Chuck McGregor about calculating sound pressure levels that has nothing to do with loudspeaker damage but is something I think should be posted on this forum!  posted_image



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Posted By: gbear14275
Date Posted: March 11, 2006 at 1:31 PM

Dyohn,

I wasn't trying to be argumentative because I agree with the too much power thing.  But...if we are talking about the myth (too little power can destroy subs) their terms(as in the meaning of the word power when people use this statement) are that power is defined according to rated specs. 





Posted By: Steven Kephart
Date Posted: March 11, 2006 at 1:51 PM

Dyohn,

Thanks!  That is exactly what I was looking for.  I remember actually reading that Rane paper a couple years ago. 

gbear14275,

I think Xtant said it best here:

"Loudspeaker power handling ratings are one of the most commonly quoted, but most poorly understood of specifications given by loudspeaker manufacturers. It seems that every company has its own way of measuring and specifying power handling. That’s because Marketing departments are always looking for ways to be able to list higher numbers for power handling in order to impress their customers with the apparent ruggedness of their products. It is sometimes difficult for product users to understand how these specifications relate to real world amplifiers or how they relate to the way they listen to their favorite kinds of music on loudspeaker systems."

Even at work, the installers I work with think manufacturer ratings are king.  I had to prove to them that sometimes the manufacturer recommended enclosure isn't an ideal choice.  Or in another case I had to show how rated impedance is generally a made up number to closely describe the actual impedance of the driver, and are quite often rated wrong.  The reason for this is because all of these ratings, including the power handling specs of car audio equipment, come from the marketing department.  Rated specs should always be taken with a grain of salt.





Posted By: willdkartunes
Date Posted: March 11, 2006 at 2:37 PM

I mentioned my "damage" to the speaker in an earlier post on this thread. For the purposes of not having to go back and try to find it I will repeat it.

As I said before, I think this damage will occur regardless if you use a box or free air. I could be wrong, but I don't think the results would differ.

The damage that I noticed had to do with the sound quality of the subwoofer. It still thumped pretty good when it was put back on a higher wattage amplifier, but the lows didn't sound as hard hitting as before, and at certain frequencies, the subwoofer had what sounded like an internal "rattle". Almost as if the subwoofer was in the early stages of getting ready to blow. It still didn't sound terrible though, and to the untrained ear it would have probably gone unnoticed. Steven may be right, and this may be due to the fact that it was free air. There is really no way to be sure unless I was to do the test again....

Of course it will still be flawed using an enclosure due to the fact that the enclosure size must be changed when switching from 500watts to 60watts of power! I also am not going to keep wasting away JL 10w7's just to prove this theory!! Trust me when I say it isn't too great for the sub running at HIGH volume at such low wattage. Of course if you keep the volume low, then the low wattage doesn't matter and you will never have a problem.

Just incase this also becomes a problem with the volume thing... I've ran that 10w7 at 80% volume for over an hour and all it did was piss off the neighbors REAL badly. The subwoofer pounds at 500 watts of power and I'm sure it is capable of doing it all day at 80% volume. (if you can stand hearing the noise for that long! lol!)

Stevdart, Your right in saying that it is just an observation. But isn't that what the majority of us do in car audio though? We observe and test and then observe some more, until we think that we are satisfied with the results. I of course was satisfied, since for one it's probably not possible to blow a subwoofer running too little power. More importantly, who would want to run a 10w7 with a mere 60 watts?!

I guess people would take my word for it if I was say, an experienced scientist, who got really indepth in my responses basically losing everyone's interest and wasting everyone's precious time in reading the over-informative scientifical conclusions of a well calculated test. I'm not going to get that crazy about this information, I assumed that my observation would be enough to give you a little insight as to what happens.... If you don't trust my word, then try it out and see, as I have also stated before. If you don't trust me, then maybe you can trust yourself.



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Do whatever makes you happy in life without diminishing the happiness of others




Posted By: DYohn
Date Posted: March 11, 2006 at 2:57 PM

It's not about trust, I'm simply trying to get a handle on what you are describing and I suspect you are simply using terms inaccurately.

First off, almost all speakers are tested in "free air" without enclosures, so operating them this way will not by itself harm anything.  Loudspeaker ratings that rely on particular enclosures are highly suspect and tend to indicate a shoddy manufacturer... Overall system power handling capability can be altered by the enclosure, which may be where you are confused.  When you say "Of course it will still be flawed using an enclosure due to the fact that the enclosure size must be changed when switching from 500watts to 60watts of power!" I don't really know what you mean.  There is no reason related to raw speaker power handling capacity that would make your statement true, so I suspect you are referring to system power design?  If you are trying to create the most efficient system or most optimal response for a particular speaker using a 500 watt amplifier VS a 60 watt amplifier, then yes, enclosure size is a major factor.... but as far as the speaker's basic thermal ratings, these are determined with no enclosure at all so size is a moot point.  There is no reason that an enclosure size has to be different just because of amplifier size, as long as the speaker will handle the power.  Please let me know what you are trying to say...?

You keep using the terms "volume" and "power" as if they are separate things.  They are inextricably tied to one another.  In order to increase the "volume" of any system you must increase "power."  So again, perhaps I simply don't understand what you mean by your use of this terminology...?

If you feed a loudspeaker a distorted and/or clipped signal, it will sound bad, yes.  If you hear a rattling or other mechanical sound inside a speaker, it is likely damaged, possibly due to a part of the voice coil separated from the former.  This is most commonly caused by excessive heat.  A JL Audio 10W7 has a thermal power rating of 500 watts.  If you damaged the voice coil, this value may have been exceeded by your test setup or the speaker may have been defective.  Is it possible for an amplifier rated at "60 watts" to generate 500 watts of thermal energy in a loudspeaker?  Yes, depending on the amplifier.  "Power" that is being used in a loudspeaker and the "ratings" listed for an amplifier can be two entirely different things.



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Posted By: DYohn
Date Posted: March 11, 2006 at 2:58 PM

gbear14275 wrote:

I wasn't trying to be argumentative because I agree with the too much power thing.  But...if we are talking about the myth (too little power can destroy subs) their terms(as in the meaning of the word power when people use this statement) are that power is defined according to rated specs. 

Thanks.  Yep, the ratings on an amplifier and the power being delivered can be two entirely different things.



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Posted By: gbear14275
Date Posted: March 11, 2006 at 3:39 PM
Totally! 




Posted By: stevdart
Date Posted: March 11, 2006 at 4:32 PM

wildkartunes wrote:

But isn't that what the majority of us do in car audio though? We observe and test and then observe some more, until we think that we are satisfied with the results.

That's the truth.  I know that is all I can do! 



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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.




Posted By: willdkartunes
Date Posted: March 12, 2006 at 5:32 PM

DYohn,

I figured that since loudspeakers were tested under free air testing that I should use this method instead of using an enclosure. I was told by Steven Kephart that the reasons for my "speaker damage" were due to the fact that I tested the speaker in a free air environment and didn't use an enclosure... That would be the only reason why I started mentioning anything about an enclosure...

Sorry about the "volume" thing. I guess I should have stated that part a little clearer. I meant the volume control of the HU or any other type of source that could be used in place of the HU. In any case, you are correct, since turning up the volume of an HU is the same as an increase in "power". Sorry if I made it seem like they were seperate things. They really aren't.

For the question about switching the enclosure size going from 500 watts to 60 watts, yes, I was referring to the overall system power design. I was only stating that IF I was to use an enclosure, that it might probably be best to use efficiency to my advantage.

Your right about the difference in thermal energy running to the loudspeaker. That could be what hindered the experiment.  I would say that if anything did go "wrong" with the experiment, then this would be the culprit. This could be the cause, but I doubt it.



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Do whatever makes you happy in life without diminishing the happiness of others




Posted By: DYohn
Date Posted: March 12, 2006 at 6:28 PM

No need to apologize abut anything, man, I was only asking my question to clarify things so I could understand what you were trying to say.  posted_image

A couple of points:  Operating a loudspeaker at high power levels in free air with tones or music signals can be very dangerous for the speaker if you don't know exactly what the speaker is capable of and how to measure it, as you can easily exceed the mechanical limits of the driver and force it to Xmech or beyond (bottom it out.)  This is why enclosures are important, and may be what was being discussed before.

Turning up the volume control on a pre-amp (head unit) can introduce clipping in the output signal going to the amp.  This causes massive amounts of high frequency (and other types) distortion and can blow voice coils easily.  This is one common cause for blown speakers, especially mains, by people trying to get more out of a system than it is capable of.  They may set their amplifier gains very carefully and never clip the amp, but if they crank the HU too much and clip the output stage of the HU, they can still blow their speakers.  I've seen it many times when idiots "crank" their volume knobs too far too often, especially with cheap-ass head units.  Volume controls often cannot be turned up past about 70%, and I've seen some crap head units that clip at about 25%.  It's important to know your gear and know what its limitations are before using it, especially for loudspeaker testing.  :)



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Posted By: willdkartunes
Date Posted: March 13, 2006 at 1:21 AM

Wow! A head unit clip at 25%!? That IS really crappy. Your totally right about that head unit thing too. This is why we tried it with the amlifier gain at full and halfway, just to make sure. With the volume at 80%, it could have still sent a clipped signal and caused the speaker to become damaged, that is true. I don't think I did because of the fact that when I had the JBL 500 watt amplifier hooked up to the subwoofer with the amplifier gain half-way (this was before I hooked it to the smaller amplifier), I put the volume at 80% and the subwoofer pounded! I kept the volume setting there and ran it through an entire CD of hip-hop. (which had quite an assortment of bass frequencies) That subwoofer beat for over an hour until the neighbors were threatening to call the cops if we didn't finally shut that thing off! lol. So I knew the subwoofer could take the volume setting on the HU without question.

When I did the same thing with the 60 watt amplifier hooked to it, the time it took to start popping and sounding terrible was almost immediately. (maybe 5 minutes) No other changes made, just the amplifier.

The head unit we were using was certainly not crappy neither. It was a Nakamichi CD-500.

It might of had something to do with the linear Xmax....

Anyway, I know for sure that the subwoofer definitely had damaged caused to it after we hooked up the smaller wattage amplifier to it. It sounds like your suggesting it was another reason for the speaker damage other than too little power....

Like I said before, this is a very tricky question to answer. Some people are 100% sold on the fact that a speaker can only be blown with too much power, but I'm not so sure. I'd say I'm more like 70/30 on this subject. (70% towards not being able to blow a speaker on too little power, 30% towards yes it could be possible) More extensive testing is needed to be done if I am to become a believer that a speaker absolutely cannot be blown off too little power.

Here is how I look at it:

I see "power" as the wattage coming from the amplifier and the "volume control" coming from the pre-amp or HU. If the "power" is too low, but the "volume control" is too high, the speaker COULD blow. If the power is too high (wattage), then it really doesn't matter too much on the volume control, because there is a pretty good chance that the speaker could blow anyway. Finally, if the power is very low AND the volume control is low, then I would definitely say that it is impossible to blow a speaker EVER.

That's my take on the subject at hand. I hope you didn't get confused by the terminology. We all see things a little different at times so if I lost you on anything, then I completely understand and that's cool. Just ask what you didn't follow like DYohn did, and I will be more than happy to try my best to clarify your confusion.



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Posted By: DYohn
Date Posted: March 13, 2006 at 1:52 AM

OK, now I think I understand you.  This statement is correct:

willdkartunes wrote:

If the power is too high (wattage), then it really doesn't matter too much on the volume control, because there is a pretty good chance that the speaker could blow anyway. Finally, if the power is very low AND the volume control is low, then I would definitely say that it is impossible to blow a speaker EVER.

The rest of your post tells me you are still suffering from several misconceptions and non-standard usage of terminology.  This statement tells me you have a lot left to learn:

willdkartunes wrote:

Like I said before, this is a very tricky question to answer. Some people are 100% sold on the fact that a speaker can only be blown with too much power, but I'm not so sure. I'd say I'm more like 70/30 on this subject. (70% towards not being able to blow a speaker on too little power, 30% towards yes it could be possible) More extensive testing is needed to be done if I am to become a believer that a speaker absolutely cannot be blown off too little power.  

It is not a tricky question to answer at all, and I have answered it over and over in this thread and elsewhere.  It's not about belief of any sort, it's not something that you need to be "sold" on.  It's science.  It's physics.  It's the way loudspeakers work.  Sorry, but you need to study this a bit more.  :)



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Posted By: Steven Kephart
Date Posted: March 13, 2006 at 2:07 AM
DYohn] wrote:

P>This is why enclosures are important, and may be what was being discussed before.


I was just pointing out to him that mechanical power handling is a function of the enclosure.  That is why he got so much excursion out of his W7 with so little power in his experiment.





Posted By: willdkartunes
Date Posted: March 13, 2006 at 4:18 PM

That was my fault. I know for a fact that is really confusing what I said. After reading what I wrote it did sound like I was then arguing the fact on whether a speaker can be blown on too much power. There is no way I would argue this fact as I know that a loudspeaker can definitely blow on too much power.

As for the too little power, I believe I stated that perfectly in my last post. I should have left the end part out because that statement just caused confusion and shouldn't have been in there.



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Posted By: Velocity Motors
Date Posted: March 21, 2006 at 4:27 PM
Adding links:


https://www.jblpro.com/pub/technote/lowpower.pdf

https://www.eaw.com/support/pdf/AmplifierPower.pdf

https://www.bcae1.com/2ltlpwr.htm

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Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA




Posted By: pumpkinman
Date Posted: March 19, 2009 at 9:54 PM
well after reading all the post.i still am yet to beleave underpowering can blow a speaker.if this is true,then everytime i turn my system down it must be underpowering.So my personal opinion is if everytime you turned your system down you would blow your speakers being underpowerd ! which i have never hurt a sub by keeping it at a low volume.. so if underpowering is blowing subs shouldnt they blow everytime you turn your system down..?

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jl-audio13w7 2 12.2 orion hccas.. massive p1500.1 amp.. american base amp 400.1 spl.. crunch 3000 pro amp..2 jl-audio 15w4d4s subs




Posted By: flogger11
Date Posted: March 22, 2009 at 10:47 AM

pumpkinman wrote:

well after reading all the post.i still am yet to beleave underpowering can blow a speaker.if this is true,then everytime i turn my system down it must be underpowering.So my personal opinion is if everytime you turned your system down you would blow your speakers being underpowerd ! which i have never hurt a sub by keeping it at a low volume.. so if underpowering is blowing subs shouldnt they blow everytime you turn your system down..?

Underpowered = running your amp wide open = A clipped sine wave (signal) = DC power to the speaker = No control, excessive heat build up = failure. END OF DISCUSSION.



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Posted By: Steven Kephart
Date Posted: March 28, 2009 at 11:46 PM
sic audio wrote:

When you clip an amp you not only increase distortion, you also compress the dynamic range of the signal... the distortion isn't what kills the speakers (except tweeters in some cases)... it's the dynamic range compression that really does it.
so it is in fact possible to blow a speaker or sub with too little power


How would that situation be too little power?




Posted By: violentmouse
Date Posted: September 22, 2009 at 1:52 AM
yeah i know "old" thread, but I felt I had to get my two cents =o)

when you have a sub that is rated at 500 watts RMS that means it can handle 500 watts max for a sustained period which means your sub has a good operational range from 1/8th of that margin. so if you hooked a 1995 model year pioneer solid state 75 watt amp to the above said subwoofer, when the amp did eventually clip your amps output signal becomes spurts of direct current rather than a smooth flow of alternating current, these short pulses of direct current would eventually heat up the voice coils 26 awg windings until the glues seperating them melted or even the windings themselves melted causing a speaker that has impaired performance. You might not EVER notice this but it can and does happen all the time. When I was a kid we used to "Rebuild" subs and the majority of our rebuilds were from people who had huge subs and tiny amps. remember a voice coil is an electromagnetic winding and therefor generates heat, it IS a resistor and resistance always generates heat, when you give a resistor a lot of direct current it will pop, but if you give that same resistor clean smooth waveforms it will last a bit longer =o)




Posted By: i am an idiot
Date Posted: September 23, 2009 at 6:16 PM

From some of these posts, I am gathering that when an amp clips, it sends DC voltage to a voice coil.  When the DC voltage gets to the coil, it must stop moving all together and burn up the coil.  I was under the impression that when an amp clips it has 2 points that the clipping is visible, one on the positive side of the waveform, and one on the negative side of the waveform.  So with a 25 WPC amplifier clipped as hard as it can be played, which of the DC voltages is damaging the speaker?   Is it the +10 volts, or is it the -10 volts?  If the amp is clipping, and the input signal is an AC voltage, how does it go from +10 to -10 without moving the cone of the woofer?  Oh wait it can't do that.  The cone of the woofer is still moving, so it is still cooling.  Clipping a small amp as severely as possible will not damage a woofer.  Unless the power handling rating of the woofer is exceeded.  The DC theory will only destroy a speaker if it is either a positive or a negative DC.  If you clip an amp, the speaker is still moving.  A moving speaker is a happy speaker.





Posted By: haemphyst
Date Posted: October 25, 2009 at 3:28 AM
flogger11 wrote:

pumpkinman wrote:

well after reading all the post.i still am yet to beleave underpowering can blow a speaker.if this is true,then everytime i turn my system down it must be underpowering.So my personal opinion is if everytime you turned your system down you would blow your speakers being underpowerd ! which i have never hurt a sub by keeping it at a low volume.. so if underpowering is blowing subs shouldnt they blow everytime you turn your system down..?
Underpowered = running your amp wide open = A clipped sine wave (signal) = DC power to the speaker = No control, excessive heat build up = failure. END OF DISCUSSION.

The end of the discussion was LONG ago. You have scratched a healing wound wide open with your COMPLETELY incorrect assertion and "end". From your "assertion", I am going to gather that you didn't even bother to read even a single word that was posted till now...

Here's your END OF DISCUSSION: You are absolutely, completely, totally, and in all other ways, WRONG.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."




Posted By: 1967type-1
Date Posted: November 06, 2009 at 10:21 PM

As a former installer who recieved factory training from both Kicker and JL Audio Techs,I was taught"too much power blows mids and highs,distortion blows subs".If you give a 250 watt (rms) rated sub,500 rms watts of undistorted signal it will play perfectly fine.But if you give the same sub 200 rms watts of a distorted (clipped) signal you are very likely to fry the voice coil.Basically from heat and the non linear movement of the speakers cone,wich causes the voice coil to move out of the magnetic gap it floats in and possibly causing it to touch the walls of the motor structure because of the non linear movement.Also the coating on the windings of the voice coil will get hot enough to bubble.This causes the sceatching sound you sometimes hear if you push the cone of a blown sub.In extreme cases it will bubble enough to make it swell enough to lock the voice coil in the gap.You may have seen this in a blown sub where you push on the spesker cone and it doesn't move in or out.Our Kicker Tech had a 12" Comp VL that was sent in and thet cut the speaker in half right through the motor structure basket cone spyder etc. so we could see the damage he was talking about.I personally have had subs come back to the shop blown,and the customer is saying how could I blow a 500 watt speaker with a 300 watt amp? The first thing I would check is where the gain was on their amp.Usuall it would be all the way up.I would try and explain to them that the gain is not a "rear volume controler" I also noticed it was easier to blow subs in a bandpass box than in sealed enclosures.Someone else mentioned in a comment about blowing subs from hard bottoming.I was taught that if your sub was bottoming out (voice coil hitting the bottom of the motor structure),then your box has a leak in it.A well sealed enclosure can't bottom out because the air inside the box becomes part of the suspension system helping to control cone motion.Limiting cone movement and preventing the voice coil from such extreme linear movement.Also most subs have bumped out back plates on the pole and magnet to help prevent it even more.



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(o\_|_/o)
67 Volkswagen Type-1 {Beetle}
Alpine CDA-7995
AudioControlEpicenter,ESP, EQL,2XS,Alpine 2 MRV-1000,MRV-F-400,Alpine R-10 Element Triple Enclosure,R-8,Kicker MB-100,2 Alpine 6.5 compoment




Posted By: i am an idiot
Date Posted: November 06, 2009 at 10:42 PM
Uh-Oh




Posted By: Steven Kephart
Date Posted: November 07, 2009 at 2:09 AM
1967type-1 wrote:

As a former installer who recieved factory training from both Kicker and JL Audio Techs,I was taught"too much power blows mids and highs,distortion blows subs".If you give a 250 watt (rms) rated sub,500 rms watts of undistorted signal it will play perfectly fine.But if you give the same sub 200 rms watts of a distorted (clipped) signal you are very likely to fry the voice coil.Basically from heat and the non linear movement of the speakers cone,wich causes the voice coil to move out of the magnetic gap it floats in and possibly causing it to touch the walls of the motor structure because of the non linear movement.Also the coating on the windings of the voice coil will get hot enough to bubble.This causes the sceatching sound you sometimes hear if you push the cone of a blown sub.In extreme cases it will bubble enough to make it swell enough to lock the voice coil in the gap.You may have seen this in a blown sub where you push on the spesker cone and it doesn't move in or out.Our Kicker Tech had a 12" Comp VL that was sent in and thet cut the speaker in half right through the motor structure basket cone spyder etc. so we could see the damage he was talking about.I personally have had subs come back to the shop blown,and the customer is saying how could I blow a 500 watt speaker with a 300 watt amp? The first thing I would check is where the gain was on their amp.Usuall it would be all the way up.I would try and explain to them that the gain is not a "rear volume controler" I also noticed it was easier to blow subs in a bandpass box than in sealed enclosures.Someone else mentioned in a comment about blowing subs from hard bottoming.I was taught that if your sub was bottoming out (voice coil hitting the bottom of the motor structure),then your box has a leak in it.A well sealed enclosure can't bottom out because the air inside the box becomes part of the suspension system helping to control cone motion.Limiting cone movement and preventing the voice coil from such extreme linear movement.Also most subs have bumped out back plates on the pole and magnet to help prevent it even more.

'




I suggest you read this entire thread and the links provided. Because all these things have been discussed in detail. For one thing you will notice that we are discussing realistic power handling and realistic power output, not made up power ratings. In fact if you follow one of the links you will see JL Audio's VP of Marketing Manville Smith included in the discussion along with engineers from Polk Audio, Harman Kardon, and some independent engineers all coming to the same conclusions as this thread has.

But if you like I could easily pick apart your points. I have a lot of experience with diagnosing blown subs.




Posted By: oldspark
Date Posted: November 13, 2009 at 7:28 AM
Go SK!

I suspect this is the thread I visited ages ago....
I was torn between laughter and wanting to offer specifics, but I read that old posts should not be reopened.

I like the "sub-cycle" being "DC". A novel approach - granted. I wonder what frequency that DC is? (LOL - DC has zero frequency; anything else is AC.)
But didn't such Fouriers go out with horses?

By the way, my underpowered engine blew up because of overheating because it wasn't powerful or fast enough to blow out the heat and.....




Posted By: blackcivichatch
Date Posted: November 13, 2009 at 7:13 PM
oldspark wrote:


By the way, my underpowered engine blew up because of overheating because it wasn't powerful or fast enough to blow out the heat and.....

LOL. That made me smile. lol

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UNLABELED Custom Car Club President





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