# Underpowering a sub?



## DC925

When is a subwoofer considered underpowered? For example, if the sub is rated to run at 500 watts, RMS cont. power. If one were to give it 100 watts, obviously that would not work. But, will that sub run effectively on say, 300-350watts?


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## fuji6

and why wouldn't giving a sub that CAN HANDLE 500 watts, 100 watts not work?

When you play your system at low levels do you think you're giving your speakers RMS wattage?

To answer the second half. I believe it's efficiency (not with just less power) is more a factor of it's design and the box you put it in. A sub may thermally handle 1000watts but (for example) in an IB setup it might reach xmax at 500.


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## Volenti

"underpowering" of subs is a thorny issue that sparks a lot of argument, if the 500w rated sub plays loud enough with a 100w input then in that case 100w is "enough" power, if it doesn't play loud enough then more power is needed.

It all gets a bit fuzzy and there's lots of "if this" and "so long as" involved, the thermal power rating it's self is a very vauge figure and depends on a lot of factors, 300w is fine for a 500w rated driver.


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## fuji6

Thanks Volenti, I probably shoulded have added some more detail like that to my reply.


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## alm001

NO WAY WOULD 100 WATTS EVER WORK, PUT 500WATTS AND DON'T EVER TURN THE VOLUME DOWN

MY SPEAKERS NEED 50WATTS, I USED TO HAVE A 49WATT AMP, AND THEY WOULDNT EVEN TURN ON. I GOT A 50W AMP AND NOW THEY ARE AWESOME. CANT TURN IT DOWN THO


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## 89grand

alm001 said:


> NO WAY WOULD 100 WATTS EVER WORK, PUT 500WATTS AND DON'T EVER TURN THE VOLUME DOWN
> 
> MY SPEAKERS NEED 50WATTS, I USED TO HAVE A 49WATT AMP, AND THEY WOULDNT EVEN TURN ON. I GOT A 50W AMP AND NOW THEY ARE AWESOME. CANT TURN IT DOWN THO


*I HOPE YOU DON'T LISTEN TO MUSIC EITHER, JUST TEST TONES.*


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## zblee

DC925 said:


> When is a subwoofer considered underpowered? For example, if the sub is rated to run at 500 watts, RMS cont. power. If one were to give it 100 watts, obviously that would not work. But, will that sub run effectively on say, 300-350watts?


I would say YES.

I have 2 subs that are 300RMS each and run both off of a 500 watt amp and work perfect with only 250RMS each...


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## Austin

alm001 said:


> NO WAY WOULD 100 WATTS EVER WORK, PUT 500WATTS AND DON'T EVER TURN THE VOLUME DOWN
> 
> MY SPEAKERS NEED 50WATTS, I USED TO HAVE A 49WATT AMP, AND THEY WOULDNT EVEN TURN ON. I GOT A 50W AMP AND NOW THEY ARE AWESOME. CANT TURN IT DOWN THO


:laugh::laugh::laugh::laugh:

So 1 watt made a difference huh? Incredible...


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## 94VG30DE

alm001 said:


> NO WAY WOULD 100 WATTS EVER WORK, PUT 500WATTS AND DON'T EVER TURN THE VOLUME DOWN
> 
> MY SPEAKERS NEED 50WATTS, I USED TO HAVE A 49WATT AMP, AND THEY WOULDNT EVEN TURN ON. I GOT A 50W AMP AND NOW THEY ARE AWESOME. CANT TURN IT DOWN THO


hahaha, I'm pretty sure this is sarcasm, but either way thanks for the fantastic new sig


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## sqshoestring

Subs that handle more power tend to be less efficient, meaning they don't go as loud on X watts as another sub that is more efficient. They have heavier everything, and that takes energy to move, to put it really simply. Subs that work right in small boxes are less efficient too in order to do that job. So what happens is they don't get as loud on 100w as another sub will. How loud you need it is another discussion. Also a large ported will be more efficient than a small sealed, using the same sub, the enclosure does change it some. An efficient sub in a large ported can use a small amp, while a beefy sub in a tiny box will need a large amp...to be somewhat comparable in performance, within reason. Also note that you need 10x the power to double the volume, that means 100w to 1,000w for double the loud. That is why there is not that much difference in say 400 to 500w.

What all that means is some sub setups will not need much amp to run, while others will need a lot more power to output typical levels people want. Something to note when you design a system or want to use particular equipment. A big mismatch will not make you happy.

To take your original post, a 500w rms sub on 50w would be roughly half as loud as 500w. So 350w is going to be something like 80% of max output. Power runs a curve to dB. 80% is not that bad, and why it would work fairly well IMO....or fairly close to what it is ultimately capable of should the ratings be correct. 100w would get you well over half the output the sub was capable of. There are other factors but roughly, anyone correct if that is off. Wattage to dB is very much a game of diminishing returns, the last watt means nothing and the first watt is the largest.


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## DC925

sqshoestring said:


> Subs that handle more power tend to be less efficient, meaning they don't go as loud on X watts as another sub that is more efficient. They have heavier everything, and that takes energy to move, to put it really simply. Subs that work right in small boxes are less efficient too in order to do that job. So what happens is they don't get as loud on 100w as another sub will. How loud you need it is another discussion. Also a large ported will be more efficient than a small sealed, using the same sub, the enclosure does change it some. An efficient sub in a large ported can use a small amp, while a beefy sub in a tiny box will need a large amp...to be somewhat comparable in performance, within reason. Also note that you need 10x the power to double the volume, that means 100w to 1,000w for double the loud. That is why there is not that much difference in say 400 to 500w.
> 
> What all that means is some sub setups will not need much amp to run, while others will need a lot more power to output typical levels people want. Something to note when you design a system or want to use particular equipment. A big mismatch will not make you happy.
> 
> To take your original post, a 500w rms sub on 50w would be roughly half as loud as 500w. So 350w is going to be something like 80% of max output. Power runs a curve to dB. 80% is not that bad, and why it would work fairly well IMO....or fairly close to what it is ultimately capable of should the ratings be correct. 100w would get you well over half the output the sub was capable of. There are other factors but roughly, anyone correct if that is off. Wattage to dB is very much a game of diminishing returns, the last watt means nothing and the first watt is the largest.


Thanks, this is very useful. I was planning on running 350 watts to the older Alpine Type R, which handles the 500.


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## Oliver

DC925 said:


> When is a subwoofer considered underpowered? For example, if the sub is rated to run at 500 watts, RMS cont. power. If one were to give it 100 watts, obviously that would not work. But, will that sub run effectively on say, 300-350watts?


A bigger box takes less power [1/2 ] , infinite baffle takes the least. [1/3 ]

A small sub box can handle the most power. [ up to 2 times ]

For a burp [ SPL term - 10 - ?? times the rated power if the mechanical end can handle it { look at Digital Designs {]

That is heat and mechanical related [ spider and surround control the cone ]


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## dolbytone

Before making a decision, please read this information that I ripped from JBL



> How do I choose the right amplifier power for my speaker system?
> 
> Ideally you should pick an amplifier that can deliver power equal to twice the speaker's continuous IEC power rating. This means that a speaker with a "nominal impedance" of 8 ohms and a continuous IEC power rating of 350 watts will require an amplifier that can produce 700 watts into an 8 ohm load. For a stereo pair of speakers, the amplifier should be rated at 700 watts per channel into 8 ohms.
> 
> A quality professional loudspeaker can handle transient peaks in excess of its rated power if the amplifier can deliver those peaks without distortion. Using an amp with some extra "headroom" will help assure that only clean, undistorted power gets to your speakers. Some professional amplifiers are designed so they have additional headroom. These amps can cleanly reproduce transient peaks that exceed the amplifier's rated power. In this case select a model with an output power rating equal to the continuous IEC power rating of the speaker. Consult the amplifier manufacturer or owner's manual to learn more.
> 
> In some applications, such as critical listening in a studio environment, it is important to maintain peak transient capability. For these applications, use an amplifier that can deliver 6db (or four times as much) more power than the continuous IEC power rating.
> 
> *If budget restraints or legacy equipment force you to use an amplifier with less power, extreme care should be taken to see that the amplifier is not driven into clipping. It may surprise you to learn that low power can result in damage to your speaker or system. Download our Danger Low Power (Adobe Acrobat, 204kB) tech note for more information.*


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## Oliver

[A quality professional loudspeaker can handle transient peaks in excess of its rated power *if the amplifier can deliver those peaks without distortion and or being clipped* quote]

A clipped signal increase the power to your speaker - solution: Buy another speaker


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## MarkZ

You can't blow a 500w speaker with 100w of amplification. It's simply not possible, UNLESS the speaker can't truly handle 500w.

JBL is using shorthand to tell you that your 100w amplifier can deliver more power than 100w if driven into clipping (but 500w is out of the question, no matter how severely you clip).


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## Oliver

DC925 said:


> When is a subwoofer considered underpowered? For example, if the sub is rated to run at 500 watts, RMS cont. power. If one were to give it 100 watts, obviously that would not work. But, will that sub run effectively on say, 300-350watts?


If it makes sound then some people are happy.

For a subwoofer to do the "Hair Trick" , you need batteries at the very least


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## DC925

I've also been eyeing are the 10w1 and 10w0 lines from JL, as well as JBL's GTO1014. The two JL's are both single VC 4 ohm, and will handle 300 and 150 rms respectively. The JBL is rated to handle 350. My amp will put out 175 @ 4 ohms and 350 @ 2. Which would you guys select? Never thought I'd put so much energy and thought into a sub choice! I mean, there all are cheap, entry level subs, but I'd rather do it right the first time and get something I'll like. I've heard the 10w1, which sounded good at the store, but I'd be going on user opinions for the others....help, guys!  Thanks all. All good info.


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## MarkZ

DC925 said:


> I've also been eyeing are the 10w1 and 10w0 lines from JL, as well as JBL's GTO1014. The two JL's are both single VC 4 ohm, and will handle 300 and 150 rms respectively. The JBL is rated to handle 350. My amp will put out 175 @ 4 ohms and 350 @ 2. Which would you guys select?


A 2 ohm sub.


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## 89grand

Again, the enclosure size and or type has a lot more to do with how loud you can get with a given amount of power over which particular sub you use. The JBL GTO's are decent subs, so are JL's (I've used both models mentioned), if you can get a good price on them.


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## DC925

89grand said:


> Again, the enclosure size and or type has a lot more to do with how loud you can get with a given amount of power over which particular sub you use. The JBL GTO's are decent subs, so are JL's (I've used both models mentioned), if you can get a good price on them.


It's a small box, but within the required specs (or pretty close) for all models, .7cf 
I was leaning towards the GTO as it also has a DVC version that I can wire in parallel.


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## 89grand

DC925 said:


> It's a small box, but within the required specs (or pretty close) for all models, .7cf
> I was leaning towards the GTO as it also has a DVC version that I can wire in parallel.


Yeah, I'm just saying the enclosure type and size dictates overall volume level more so than the particular sub. With the said, I drive two 10W0's with one 200 watt PPI A200 and it got pretty loud. The subs were in a sealed enclosure of about 1.5 ft3.


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## Oliver

PRICE INCLUDES (3) REX10D4 CAR SUBWOOFERS TOTALING 525 WATTS RMS!

3) RE AUDIO REX10D4 REX 10" D4 DVC CAR SUBWOOFERS REX10 - eBay (item 350335984311 end time Aug-30-10 01:34:14 PDT)

I've had guys say they would put these up against an IDMAX sub for output and sound , plus you won't have to part with 4 times the money 

3) RE AUDIO REX10D4 REX 10" D4 DVC CAR SUBWOOFERS REX10
PACKAGE DEAL: (3) REX10D4+ *FREE SHIPPING!*
Price:	*US $139.95*

Can mount 2 and have one back in case something unfortunate happens [ won't have to build a new box].


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## sqshoestring

If your amp is rated [email protected] ohms then get the sub you can run that way. I ran four DVC 12s on my kicker 5ch at 420rms, had this v12 alpine 5ch I wanted to test. Note I had it EQ'd to play low, had a bump at 30-35Hz and pretty flat otherwise, and the infintiy 12s were rated 300rms each but 150rms each IB like I ran them. The alpine was only rated at 4 ohms 150rms....not supposed to run it 2 ohms. So I hooked it up at 8 ohms. It sounded great, that must have been around 100rms or something total. But it didn't go that loud, it would go a little louder than a stock system the difference was it would put out 30Hz no problem. It was barely enough to hear good bass with all the windows down. On the 420rms that was still well under the 600 total they were rated for IB, it went pretty loud for SQ use. There was no way the 4x70 on highs could keep up with it running all four doors, the rear of the car would shake and rattle, it was more than I needed.


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## GibTG

As others may have mentioned, the configuration of the woofer (sealed, vented, infinite baffle) have a large affect on the thermal rating of the woofer as well.

For sound quality in a car, it's easy to make enough SPL in the bass frequncies. So, if you have a big hefty sub in a vented or open air configuration it won't need a lot of power to do it's job. If you want to make a ton of SPL, that's a whole different story.


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## DC925

Yeah, going to go small and sealed (.7cf3), so I'm looking at different subs' T/S specs to try and find one that will accomplish my goal. The JL is starting to pull in front, followed by the GTO. Tough choice.


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## sqshoestring

You should model them, its harder to find a lower priced sub that will work well in a small box. Many of them do spl in a small box, meaning they blast at 50Hz and up and you don't get any 40 and below. A small box sub will be less efficient but have a smoother response in general. Well, unless your car has a lot of cabin gain and/or you like that kind of sound. I tend to like low bass more so I am careful about spl-ish subs. I do have an MTX 4510 that sounds nice in a .87 sealed MTX box, it was one of the few I tried that I could live with. I keep it for a temp sub. Has less output of course but sounds much nicer than half a dozen cheaper mass produced 12s I tried in a 1.25 box. Even one of the infinity I used IB had a big peak at 50Hz in a sealed they recommended even though it had a 24Hz Fs and .46 Qts. The other 12s were Sony P3, Audiobahn clone, Jensen, digital designs, some off names, etc.


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## DC925

I used to run an older Type R (the 300 watt version) in a 1 ft cube enclosure, and it sounded great (shook mirrors, audible outside, etc.) but that was when I had a GLI Jetta and it punched into the cabin without a hitch. I'd have gone the same route except it's going into my commuter car (99 Miata) and the trunk is TINY. In fact the box I bought barely fits in there! Thanks for the input though, appreciate it.


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## sqshoestring

Type R is a pretty good sub from what I know, I nearly bought some a while back. If you like higher/tighter bass then you have less to worry about. Sometimes I wish I did, tossing a box in the trunk is infinitely easier than making an IB baffle in most cases.


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## Rob J

MarkZ said:


> You can't blow a 500w speaker with 100w of amplification. It's simply not possible, UNLESS the speaker can't truly handle 500w.
> 
> JBL is using shorthand to tell you that your 100w amplifier can deliver more power than 100w if driven into clipping (but 500w is out of the question, no matter how severely you clip).



I come from a Professional Audio background, and I have to disagree with the above statement. It is actually easier to damage a loudspeaker with less power than more. Once that amp goes into clipping, you begin to send DC voltage to the speakers, and we all know that speakers don't like DC voltage.


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## MarkZ

Rob J said:


> I come from a Professional Audio background, and I have to disagree with the above statement. It is actually very easy to damage a loudspeaker with less power than more. One that amp goes into clipping, you begin to send DC voltage to the speakers, and we all know that speakers don't like DC voltage.


1) Speakers don't dislike DC. There's nothing inherent in DC that will harm speakers, UNLESS the speaker uses cone motion as a significant means of cooling itself. If you feed DC to a speaker, the cone won't move. When you clip an amp, the cone moves just as much as it ever did.

2) When an amp clips, it DOES NOT produce DC. Don't believe me? Clip your amp and measure the DC voltage with your meter.


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## sqshoestring

MarkZ said:


> 1) Speakers don't dislike DC. There's nothing inherent in DC that will harm speakers, UNLESS the speaker uses cone motion as a significant means of cooling itself. If you feed DC to a speaker, the cone won't move. When you clip an amp, the cone moves just as much as it ever did.
> 
> 2) *When an amp clips, it DOES NOT produce DC.* Don't believe me? Clip your amp and measure the DC voltage with your meter.


It does on a scope 


But I agree it does not necessarily blow a speaker. It does create more power under the curve so to speak, but no more than double clean RMS unless its a real pile of an amp and at that point the music would be barely audible...thus that issue would be user error, maybe user idiocy. This is provided the xmax has not been exceeded causing mechanical damage.

A sub blows dependent on its cooling also; if its not that good at cooling it may take a lot of power for a short time, then blow on just over rated if played for a long period. Its just like an amp with hardly any fins on the case/sink and no fan, it will play hard for a while but long term high output it will always overheat if you don't have a fan on it to move more air over it. (given class D needs less fins as it makes less heat in operation)

On top of all that, just how does a manufacturer rate a sub? Who knows.


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## MarkZ

sqshoestring said:


> It does on a scope


Then your scope is broken.

Do this with your scope: flip the switch to AC, so that DC is blocked. Do you still see the clipped waveform?


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## Oliver

Rob J said:


> I come from a Professional Audio background, and I have to disagree with the above statement. It is actually easier to damage a loudspeaker with less power than more. Once that amp goes into clipping, you begin to send DC voltage to the speakers, and we all know that speakers don't like DC voltage.


How much for whatever you are smoking ?

What exactly led you to believe this ? A meter ? An oscilloscope ? *A guess *


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## Rob J

a$$hole said:


> How much for whatever you are smoking ?
> 
> What exactly led you to believe this ? A meter ? An oscilloscope ? *A guess *


20+ years of real world experience in pro audio. I've seen many more loudspeaker transducers damaged by being underpowered, than overpowered.


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## 89grand

You simply cannot damage a speaker from "under powering" it. It's impossible other wise all speakers would be damaged with music.


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## Rob J

89grand said:


> You simply cannot damage a speaker from "under powering" it. It's impossible other wise all speakers would be damaged with music.


This is true as long as the amplifier is not clipping. Now once an amp goes into clipping, it is a different ball game. 95% of all loudspeaker damage in the world has occurred from not enough CLEAN power, vs too much clean power having been applied.

I've been designing and installing Professional Audio, Video and Automation Systems for more than twenty years. eg: Night Club Systems, Sports Bars, Restaurants, Hotels, Boardrooms, ect...

I have also been a JBL Pro, Crown, BSS Audio, Crestron, ect.... dealer for many years. So, I've seen and experienced my fair share of loudspeaker damage, and it's causes.

Rob.


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## sqshoestring

An amplifier can only make double the power outputting a square wave that would be massive distortion. So sure if you have 150w speakers on 100w amp, it is possible to exceed ratings....assuming those ratings are correct for what you are doing.


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## MarkZ

Rob J said:


> This is true as long as the amplifier is not clipping. Now once an amp goes into clipping, it is a different ball game. 95% of all loudspeaker damage in the world has occurred from not enough CLEAN power, vs too much clean power having been applied.


Bull-oney. 



> I've been designing and installing Professional Audio, Video and Automation Systems for more than twenty years. eg: Night Club Systems, Sports Bars, Restaurants, Hotels, Boardrooms, ect...
> 
> I have also been a JBL Pro, Crown, BSS Audio, Crestron, ect.... dealer for many years. So, I've seen and experienced my fair share of loudspeaker damage, and it's causes.
> 
> Rob.


Explain *how* too little power (clipped) can blow a speaker whereas more power will not. The only mechanistic argument you've offered so far was based on a false premise (that a clipped signal contains DC).


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## 89grand

Considering you can only damage a woofer from exceeding it's thermal or mechanical limits, under powering is not the cause. Over powering it is. If I ran a sub off a head unit and turned it all the way up so that it was distorting massively, the sub would never be damaged no matter how long I left it playing.


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## Rob J

89grand said:


> Considering you can only damage a woofer from exceeding it's thermal or mechanical limits, under powering is not the cause. Over powering it is. If I ran a sub off a head unit and turned it all the way up so that it was distorting massively, the sub would never be damaged no matter how long I left it playing.


In that scenario, you are correct. But that's not a fair or a real world comparison. Let's talk more about a "real world" scenario. For example, let's say this guy has a subwoofer that is rated to handle 250 watts, so he is powering it with a 250watt amp. Now, he's cruising down the road, over driving his system, and constantly forcing that 250 watt amp into clipping. Now, the guy next to him has the same sub, but with a 500 watt amp. Since this guy has a bit more headroom, he doesn't need to force the 500 watt amp into clipping as the first guy. He's feeding the sub clean power, albeit more than it is rated for.

Which sub do you think is going to last longer?

I see these types of scenarios in the Pro Audio world all the time, especially in the night club environment. Most night club systems that have constant problems are underpowered, not over powered. When we design our systems, we always prefer to have at least double the clean power than the ratings on the speakers rather than at or under the rating. And, as you've read above, even JBL PRO advises this. How are you going to argue with the engineers at JBL Pro? Headroom is king. Now, of course, we don't want to be clipping those amps, because, yes we will fry the transducers. But, with extra headroom, and BSS Audio Sound Web processor's, we can control that clipping on over zealous DJ's. It's is much easier to control a system that is over powered than under. 

I have clients whom have systems we've installed 10+ years ago, and have never blown a driver. All because of my design philosophy.


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## Rob J

http://www.jblpro.com/catalog/support/getfile.aspx?docid=246&doctype=3


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## 89grand

Rob J said:


> http://www.jblpro.com/catalog/support/getfile.aspx?docid=246&doctype=3



That particular white paper seems to addressing high frequency drivers, which of course are much more likely to get damaged, but this thread is specifically about "under powering" subwoofers.©


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## sqshoestring

If speakers cared about distortion, Jimi Hendrix would have blown half the speakers out there. Unless its so distorted it can't move the driver to cool it, and again that is pure idiocy because its not music.


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## TrickyRicky

I agree with those stating that if 100watts is loud and sound good, why would you need 500watts???


I power my 1000watt Strokers with only 250watt or 500watts and they sound very identical. So why would I want to use a 1000watt amp when 250watts sounds a lot like 500watts (and at that sound amazing and loud).

And no my amps dont clip, and if they do I can barely notice. Unlike other amps, they clip and sound horrible.


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## MarkZ

Rob J said:


> In that scenario, you are correct. But that's not a fair or a real world comparison. Let's talk more about a "real world" scenario. For example, let's say this guy has a subwoofer that is rated to handle 250 watts, so he is powering it with a 250watt amp. Now, he's cruising down the road, over driving his system, and constantly forcing that 250 watt amp into clipping. Now, the guy next to him has the same sub, but with a 500 watt amp. Since this guy has a bit more headroom, he doesn't need to force the 500 watt amp into clipping as the first guy. He's feeding the sub clean power, albeit more than it is rated for.
> 
> Which sub do you think is going to last longer?
> 
> I see these types of scenarios in the Pro Audio world all the time, especially in the night club environment. Most night club systems that have constant problems are underpowered, not over powered. When we design our systems, we always prefer to have at least double the clean power than the ratings on the speakers rather than at or under the rating. And, as you've read above, even JBL PRO advises this. How are you going to argue with the engineers at JBL Pro? Headroom is king. Now, of course, we don't want to be clipping those amps, because, yes we will fry the transducers. But, with extra headroom, and BSS Audio Sound Web processor's, we can control that clipping on over zealous DJ's. It's is much easier to control a system that is over powered than under.
> 
> I have clients whom have systems we've installed 10+ years ago, and have never blown a driver. All because of my design philosophy.


Still waiting for you to explain why less power would destroy a speaker before more power would.


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## Christolei

Underpowering, distorsion and clipping are leading causes of damaged woofers, although your woofers will work with less power it's always better to match them well.


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## 89grand

Christolei said:


> *Underpowering, distorsion and clipping are leading causes of damaged woofers*, although your woofers will work with less power it's always better to match them well.


We've already established that isn't true.

Not that anyone here is recommending using a small amp on their subwoofers, but it won't damage the woofer.©


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## Oliver

Christolei said:


> Underpowering, distorsion and clipping are leading causes of damaged woofers, although your woofers will work with less power it's always better to match them well.


Never listen to Jimi Hendrix and always crank your head unit to the max before you turn your car off and never trim your nails in the car


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## dolbytone

I think this "disagreement" is the result of some misunderstanding due to the difference between what is being said and the underlying meaning or intent of some of the posts.

First it should be understood that Jimi Hendrix probably achieved his distortion not by overdriving his amps/speakers but by saturating his signal going into his amplifier. Thus I think for the most part he was not clipping his amps, but safely reproducing the distorted input signal, which makes this analogy somewhat irrelevant to this discussion.

Now, it seems like everyone disagrees with Rob J, and taken literally it is true that you can't blow a speaker with too little power. I think we all understand that when you drive an amplifier too hard and it clips for a prolonged period, the result can be either a failure of the amplifier, and/or a failure of the speaker it is driving due to the potentially double power output of the amplifier if the speaker is not capable of handling more than double the rated power of the amplifier.

The bottom line is that this is a poorly designed audio system in that you have obviously put more demand on the amplifier than it is capable of handling. So in essence the damage to the speaker was caused by the utilization of an underpowered amplifier even if this is not true in literal terms.

I design sound systems for movie theaters and when I spec out an auditorium I know a few things beforehand like the cubic feet of the room, and the target dynamic range of the sound system. Basically the bigger the room, the more speakers I install, the more speakers I install, the more amplifiers I install. I don't just buy bigger amps or just turn the amps up more. I make sure that I can hit my target room SPL without driving the amplifiers into clipping. If that means I have 6 subwoofers in the auditorium then so-be-it, I'll use 6 subs and three 2 channel amps with the gains set to a level that will not overpower the drivers.

Bottom line: If you want it louder then add speakers/amps. Don't turn your amps up to the point that you will clip them, and choose speakers that can more than handle what power you plan to deliver under the most strenuous reproduction conditions your sound system will be made to endure.


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## MarkZ

dolbytone said:


> I think this "disagreement" is the result of some misunderstanding due to the difference between what is being said and the underlying meaning or intent of some of the posts.
> 
> First it should be understood that Jimi Hendrix probably achieved his distortion not by overdriving his amps/speakers but by saturating his signal going into his amplifier. Thus I think for the most part he was not clipping his amps, but safely reproducing the distorted input signal, which makes this analogy somewhat irrelevant to this discussion.


Seriously? Most of Jimi's "fuzz" came from overdriving his amplifier. The same is true for many many guitar players. It's usually the more "electronic" sounding distortion (think metal) that has more well-behaved distortion.



> Now, it seems like everyone disagrees with Rob J, and taken literally it is true that you can't blow a speaker with too little power. I think we all understand that when you drive an amplifier too hard and it clips for a prolonged period, the result can be either a failure of the amplifier, and/or a failure of the speaker it is driving due to the potentially double power output of the amplifier if the speaker is not capable of handling more than double the rated power of the amplifier.


I don't think everyone understand this, actually. There are truly some people here who think that you're more likely to blow your subwoofer by clipping a 50w amp than by delivering an unclipped 500w signal to the sub.


----------



## DC925

Welp, I went ahead and bought myself an MTX TR5510-44, rated @ 300 watts RMS, which is rated slightly under what I can provide it @ 2 ohms. This has been a great thread however, and I'm learning a lot from you guys. I don't know if MTX is the the same MTX that gave us Black Gold, Blue Thunder, etc., but it seems to be an OK sub. Will try and provide a review once I have it up and running. It's a shame that they've outsourced to China, but that seems to be the trend these days... thanks everyone. I'm almost regretting sending back the Polk MM 10", which was def. a better woofer, at least as far as build quality. Thanks all....


----------



## Rob J

dolbytone said:


> I think this "disagreement" is the result of some misunderstanding due to the difference between what is being said and the underlying meaning or intent of some of the posts.
> 
> First it should be understood that Jimi Hendrix probably achieved his distortion not by overdriving his amps/speakers but by saturating his signal going into his amplifier. Thus I think for the most part he was not clipping his amps, but safely reproducing the distorted input signal, which makes this analogy somewhat irrelevant to this discussion.
> 
> Now, it seems like everyone disagrees with Rob J, and taken literally it is true that you can't blow a speaker with too little power. I think we all understand that when you drive an amplifier too hard and it clips for a prolonged period, the result can be either a failure of the amplifier, and/or a failure of the speaker it is driving due to the potentially double power output of the amplifier if the speaker is not capable of handling more than double the rated power of the amplifier.
> 
> The bottom line is that this is a poorly designed audio system in that you have obviously put more demand on the amplifier than it is capable of handling. So in essence the damage to the speaker was caused by the utilization of an underpowered amplifier even if this is not true in literal terms.
> 
> I design sound systems for movie theaters and when I spec out an auditorium I know a few things beforehand like the cubic feet of the room, and the target dynamic range of the sound system. Basically the bigger the room, the more speakers I install, the more speakers I install, the more amplifiers I install. I don't just buy bigger amps or just turn the amps up more. I make sure that I can hit my target room SPL without driving the amplifiers into clipping. If that means I have 6 subwoofers in the auditorium then so-be-it, I'll use 6 subs and three 2 channel amps with the gains set to a level that will not overpower the drivers.
> 
> Bottom line: If you want it louder then add speakers/amps. Don't turn your amps up to the point that you will clip them, and choose speakers that can more than handle what power you plan to deliver under the most strenuous reproduction conditions your sound system will be made to endure.



Thank You.

The bottom line is, far more speakers are damaged from a lower powered amp that is severely over driven, vs the number of speakers that are blown or damaged from being cleanly overpowered. (w/o clipping)

End of discussion. My twenty plus years of real world experience has taught me this, and I stand my ground respectfully, but firmly.


----------



## dolbytone

MarkZ said:


> Seriously? Most of Jimi's "fuzz" came from overdriving his amplifier. The same is true for many many guitar players. It's usually the more "electronic" sounding distortion (think metal) that has more well-behaved distortion.


Well now that I think about it, I'm sure Jimi was using tube amps which is a different animal than what we are discussing in this thread.


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## Rob J

sqshoestring said:


> If speakers cared about distortion, Jimi Hendrix would have blown half the speakers out there. Unless its so distorted it can't move the driver to cool it, and again that is pure idiocy because its not music.


And actually, he did blow a good bit of speakers during concerts. I've been to numerous JBL Pro, BSS Soudweb trainings, and this topic of discussion regarding Hendrix has comes up fairly often.

But also keep in mind that a lot of his distortion was generated in the line level, pre-amp stage, not necessarily from constant power amp clippage. These are two different animals here.


----------



## Oliver

Pete Townsend smashed his guitars - windmilled em , Jimi lit his on fire , etc..,

Drummers busted up their drumsets . . .

*Here's what your missin - If their payin , I'm playin !*

*I M A G E* 

*people buying and under powering their car audio is a cross of being - misinformed and broke*


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## Christolei

How about this for a compromise, If you are going to underpower your speakers plz make sure your speakers can handle at least 3 times more power than your amp can produce...


----------



## Rob J

MarkZ said:


> I don't think everyone understand this, actually. There are truly some people here who think that you're more likely to blow your subwoofer by clipping a 50w amp than by delivering an unclipped 500w signal to the sub.


If referring to me no, I don't believe that, and I never stated that you could blow a subwoofer rated at say 500 watts with a 50 watt amp. However you are much more likely to blow that 500 watt rated sub with a 500 watt amp, than you are with a 1000 watt amp if you are pushing that 500 watt amp hard, (into clipping) Now, of course if you push that 1000 watt amp into clipping, expect that 500 watt sub to go up in smoke like Cheech and Chong. However, pushing that 1000 watt amp fairly hard, but not into clipping, it is doubtful that sub will not be damaged as long as it is not pushed past it's mechanical limits.

With quality Pro Audio transducers, this is true all day long. Which is why I state again, I always design my systems with roughly double the power as the continuous power rating of transducers or boxes.

For example the JBL 2226H, and the 2242H drivers are perfect examples. They are top shelf drivers that I have used for many years. A 2226H is rated at 600 watts continuous. I always feed them with roughly 1200 watts. They can easily take it, as long as the amp is not driven into clipping. We typically use Crown power, so quality power is a must too. Many cheaper pro audio amps become very unstable once you drive them into clipping, thus causing blown drivers.


----------



## MarkZ

Rob J said:


> And actually, he did blow a good bit of speakers during concerts. I've been to numerous JBL Pro, BSS Soudweb trainings, and this topic of discussion regarding Hendrix has comes up fairly often.
> 
> But also keep in mind that a lot of his distortion was generated in the line level, pre-amp stage, not necessarily from constant power amp clippage. These are two different animals here.


How are they two different animals?

You said earlier that a clipped wave, because of its flat regions, is harmful to a speaker. If you generate a clipped wave with flat regions at the preamp level, then it should be just as harmful, should it not?

I think the analogies that have been brought up are very fitting, because it proves the ridiculousness that clipped waves are intrinsically harmful to speakers.

Your observations in your twenty years are, unfortunately, due to a logical confound. POWER KILLS SPEAKERS. When you clip an amp, you deliver more power into a speaker than when you don't clip the amp. So, instead of attributing the blown speakers to the increase in power, you attribute it to clipping itself. This is your mistake.


----------



## MarkZ

Rob J said:


> If referring to me no, I don't believe that, and I never stated that you could blow a subwoofer rated at say 500 watts with a 50 watt amp. However you are much more likely to blow that 500 watt rated sub with a 500 watt amp, than you are with a 1000 watt amp if you are pushing that 500 watt amp hard, (into clipping) Now, of course if you push that 1000 watt amp into clipping, expect that 500 watt sub to go up in smoke like Cheech and Chong. However, pushing that 1000 watt amp fairly hard, but not into clipping, it is doubtful that sub will not be damaged as long as it is not pushed past it's mechanical limits.
> 
> With Pro Audio transducers, this is true all day long. Which is why I state again, I always design my systems with roughly double the power as the continuous power rating of transducers or boxes.


Like I said 3 days ago, I'm still waiting for you to explain HOW less power would destroy a speaker before more power would. You can insist it's true all you want. But it doesn't make it true. Tell us by what mechanism less power, and therefore less energy and less heat, will blow a speaker.


----------



## dolbytone

Christolei said:


> How about this for a compromise, If you are going to underpower your speakers plz make sure your speakers can handle at least 3 times more power than your amp can produce...


If you design your system like this it is equivalent to intentionally building distortion into your sound system. I can't think of any situation where this is a positive thing in car audio.


----------



## Rob J

BTW Oliver, bring back that avatar you recently had. I always enjoyed looking at that nice UPS girl:beerchug:


----------



## MarkZ

Christolei said:


> How about this for a compromise, If you are going to underpower your speakers plz make sure your speakers can handle at least 3 times more power than your amp can produce...


Are you serious?

You're saying this... if you have a 250w amp... you're ok if you have a 250w speaker (that's not underpowering, right?). But you're not ok if you have a 500w speaker (now you're underpowering), but you're ok if you have a 750w speaker (it's 3x your amp's power rating).

Do you realize how logically out of whack that is?


----------



## Christolei

dolbytone said:


> If you design your system like this it is equivalent to intentionally building distortion into your sound system. I can't think of any situation where this is a positive thing in car audio.


I 4 sure never recommend under powering your speakers but should 1 decide to do so, that's the safest formula to reduce the risk of blowing them...


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## MarkZ

Speakers don't know whether you're delivering the original signal or a distorted version of the original signal.

I wish just one person from the "clipping blows speakers" crowd would answer the question I've repeatedly asked: what is it about a clipped signal that blows speakers before more power would? If you can't answer this question, then you have no business claiming that it does.


----------



## Rob J

MarkZ said:


> How are they two different animals?
> 
> You said earlier that a clipped wave, because of its flat regions, is harmful to a speaker. If you generate a clipped wave with flat regions at the preamp level, then it should be just as harmful, should it not?
> 
> I think the analogies that have been brought up are very fitting, because it proves the ridiculousness that clipped waves are intrinsically harmful to speakers.
> 
> Your observations in your twenty years are, unfortunately, due to a logical confound. POWER KILLS SPEAKERS. When you clip an amp, you deliver more power into a speaker than when you don't clip the amp. So, instead of attributing the blown speakers to the increase in power, you attribute it to clipping itself. This is your mistake.



I understand where you are coming from, but the issue is, you are taking it into literal terms, and not understanding the REAL WORLD concept. I totally understand that when an amp clips, you are driving it past its limits, and it is being forced to output more wattage than it was designed for, and that it can actually double it's rated power. I Know this. BUT, and a big BUT, lots of sound systems, whether they are Pro Audio, Home Audio, or Car Audio, are not matched properly. So, often times, people are are always trying to force more out of that amp, so what happens, it starts running hot, it starts to become unstable, the impedance is altered from the instability, thus frying your voice coil. Now, I do understand that literally the driver got damaged from too much power, yes, I get it. But, it was not clean power, and that was the primary issue. If that system would have been over powered accordingly, and the amp was working hard, but still maintaining stability, it would have been far less likely to have damaged the drivers. 

THIS is the reason we state that under powering a speaker is more dangerous than overpowering it. Even though technically, yes it got damaged from excessive power. Even JBL Pro recommends this design philosophy. How can you argue with JBL PRO?

I say it's time I buy us all a round of beer.:beerchug:


----------



## Rob J

MarkZ said:


> Are you serious?
> 
> You're saying this... if you have a 250w amp... you're ok if you have a 250w speaker (that's not underpowering, right?). But you're not ok if you have a 500w speaker (now you're underpowering), but you're ok if you have a 750w speaker (it's 3x your amp's power rating).
> 
> Do you realize how logically out of whack that is?



I gotta agree with Mark on this one. That's a little out there.


----------



## MarkZ

Rob J said:


> I understand where you are coming from, but the issue is, you are taking it into literal terms, and not understanding the REAL WORLD concept. I totally understand that when an amp clips, you are driving it past its limits, and it is being forced to output more wattage than it was designed for, and that it can actually double it's rated power. I Know this. BUT, and a big BUT, lots of sound systems, whether they are Pro Audio, Home Audio, or Car Audio, are not matched properly. So, often times, people are are always trying to force more out of that amp, so what happens, it starts running hot, it starts to become unstable, the impedance is altered from the instability, thus frying your voice coil. Now, I do understand that literally the driver got damaged from too much power, yes, I get it. But, it was not clean power, and that was the primary issue. If that system would have been over powered accordingly, and the amp was working hard, but still maintaining stability, it would have been far less likely to have damaged the drivers.
> 
> THIS is the reason we state that under powering a speaker is more dangerous than overpowering it. Even though technically, yes it got damaged from excessive power. Even JBL Pro recommends this design philosophy. How can you argue with JBL PRO?
> 
> I say it's time I buy us all a round of beer.:beerchug:


Right, but it's not a matter of "real world" here. What I'm saying is about as real world as you can get. You seem to think that the solution to a low power amp blowing speakers is to buy a bigger amp. I'm telling you that you're just as likely to blow the speaker if you increase the size of the amp.

Whether it's 500w of distorted power or 500w of clean power ... it's still 500w, and by definition generates the same amount of heat in both cases.

If your speaker can't handle 500w, then it's not the amp that needs to be upgraded ... it's the speaker.


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## Rob J

MarkZ said:


> Speakers don't know whether you're delivering the original signal or a distorted version of the original signal.
> 
> I wish just one person from the "clipping blows speakers" crowd would answer the question I've repeatedly asked: what is it about a clipped signal that blows speakers before more power would? If you can't answer this question, then you have no business claiming that it does.


It's simple Mark. Because when you overdrive and clip most power amps, they tend to loose there stability, impedances change, thus the loads become more demanding on the amplifier and unstable, you get wattage spikes from that instability and the speaker doesn't like that. The amp being stressed, then puts a greater stress on the driver, thus causing problems.


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## Oliver

A Lack of Knowledge can achieve many things


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## Christolei

MarkZ said:


> Are you serious?
> 
> You're saying this... if you have a 250w amp... you're ok if you have a 250w speaker (that's not underpowering, right?). But you're not ok if you have a 500w speaker (now you're underpowering), but you're ok if you have a 750w speaker (it's 3x your amp's power rating).
> 
> Do you realize how logically out of whack that is?


What am saying is:
If your speakers rating is the same power handling as your amplifier is cleanly capable of producing, pushing them with a clipped signal for extended periods of time may cause speaker damage and/or premature failure.

If your speakers rating is the same power handling as your amplifier is cleanly capable of producing, pushing them with a square wave signal for extended periods of time will likely cause speaker damage. 

If your speakers are capable of handling a lot more than your amplifier can produce, driving them with a clipped signal will not likely hurt them. If the speakers can handle 3 to 4 times that of the amp, there is virtually no blowing risks no matter how long you are clipping.
The danger zone in under powering (*not that I recommend under powering in any way shape or form*) is under 3 times that of the amp more like twice the power to the exact power rating...

I agree with the recommendation of matching your speaker with an amp twice it's rated power.


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## dolbytone

Christolei said:


> I 4 sure never recommend under powering your speakers but should 1 decide to do so, that's the safest formula to reduce the risk of blowing them...


I see what your point is but either way you will have to replace the amp when it fails. What I am suggesting is that if you are clipping your amp, you bought the wrong amp or not enough amps. Everyone seems caught up in this amp/speaker relationship and it's not really about that. It's really about the how loud you want it and amp/speaker package relationship.


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## Rob J

MarkZ said:


> Right, but it's not a matter of "real world" here. What I'm saying is about as real world as you can get. You seem to think that the solution to a low power amp blowing speakers is to buy a bigger amp. I'm telling you that you're just as likely to blow the speaker if you increase the size of the amp.
> 
> Whether it's 500w of distorted power or 500w of clean power ... it's still 500w, and by definition generates the same amount of heat in both cases.
> 
> If your speaker can't handle 500w, then it's not the amp that needs to be upgraded ... it's the speaker.



I understand where you are coming from. I never suggested a general statement where a solution would be to buy a larger amp. Every system design has to be taken on a case by case analysis. The solution is, system design. Bottom line. Whether is it Pro, Home, Car, it's all about the design. But I still stand firm in my belief that under powering kills more than over powering. But, that statement is not meant to be taken literally. Hopefully you understand my point, as I do understand yours.

Peace. Gotta hit the sack. Need to get up at a reasonable hour tomorrow, so I can try and get some more work done on my truck install.


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## Christolei

dolbytone said:


> I see what your point is but either way you will have to replace the amp when it fails. What I am suggesting is that if you are clipping your amp, you bought the wrong amp or not enough amps. Everyone seems caught up in this amp/speaker relationship and it's not really about that. It's really about the how loud you want it and amp/speaker package relationship.


Could not agree more... 
If 1 goes ahead and spend money on upgrading his sound system, he then should get the right amp...
This is why I am asking for help with this thread: http://www.diymobileaudio.com/forum/no-question-dumb-forum/87709-amp-selection-porsche-996-a.html


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## MarkZ

Rob J said:


> It's simple Mark. Because when you overdrive and clip most power amps, they tend to loose there stability, impedances change, thus the loads become more demanding on the amplifier and unstable, you get wattage spikes from that instability and the speaker doesn't like that. The amp being stressed, then puts a greater stress on the driver, thus causing problems.


Impedances don't change, except to go UP with temperature.

Anyway, how does the amp being stressed transform that stress into the speaker being stressed? If you're lifting weights that are too heavy for you, you stress your muscles. But that doesn't mean you're also stressing the dumbbell.


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## 94VG30DE

Rob J said:


> It's simple Mark. Because when you overdrive and clip most power amps, they tend to loose there stability, impedances change, thus the loads become more demanding on the amplifier and unstable, you get wattage spikes from that instability and the speaker doesn't like that. The amp being stressed, then puts a greater stress on the driver, thus causing problems.


I don't understand how an amp that clips all of a sudden can temporarily make more power, and then this new-found power can not be withstood by the speaker. Seems like any physics-defying tiny-burst of power from an amp would also be tiny enough to be simply absorbed and ignored by the speaker. Even if the amp could spontanteously create more voltage than it is normally capable of, would the speaker really be the thing to be worrying about in that instance? 

My idea is this. Have someone hook up two identical 100w subs, one to a 25w amp with the gain full up and clipping like a fiend, and then the other hooked up to a 100w amp. Then we see which sub smokes first, and post the video on youtube for everyone to see.


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## MarkZ

I think he meant that a clipped signal (think square wave) intrinsically has more energy than a sine wave of the same amplitude. Since amplifiers are usually measured with sine waves in mind, then a clipped signal can exceed that rating.

I believe this might be what he meant by "wattage spike", but I don't know for sure.

In any case, yeah, we should be looking at this problem in terms of power content within the speaker's passband. That's the _only_ thing can potentially damage a speaker. Not including screwdrivers.


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## Oliver

> _ But that doesn't mean you're also stressing the_* dumbbell.*


:beerchug:


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## ttocs388

what happens when it clips the signal, is that it takes the nice smooth tops and bottoms off of the ac signal. When it does this it then feeds short bursts of DC voltage to the speaker at what ever the max voltage is that the amp will let out(usually too high for the speaker). There is nothing worse for a speaker then DC, this forces the speaker to move to its peak(either in or out) and then hold it while for the duration of the clipping. This is very hard on the speaker and develops heat very quickly and will lead to a blown/burned speaker.


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## MarkZ

ttocs388 said:


> what happens when it clips the signal, is that it takes the nice smooth tops and bottoms off of the ac signal. When it does this it then feeds short bursts of DC voltage to the speaker at what ever the max voltage is that the amp will let out(usually too high for the speaker). There is nothing worse for a speaker then DC, this forces the speaker to move to its peak(either in or out) and then hold it while for the duration of the clipping. This is very hard on the speaker and develops heat very quickly and will lead to a blown/burned speaker.


There is no such thing as alternating DC!


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## sqshoestring

ttocs388 said:


> what happens when it clips the signal, is that it takes the nice smooth tops and bottoms off of the ac signal. When it does this it then feeds short bursts of DC voltage to the speaker at what ever the max voltage is that the amp will let out(usually too high for the speaker). There is nothing worse for a speaker then DC, this forces the speaker to move to its peak(either in or out) and then hold it while for the duration of the clipping. This is very hard on the speaker and develops heat very quickly and will lead to a blown/burned speaker.


You need a scope MarkZ....

None the less, the above does not happen. The speaker due to its suspension does not instantly stop while the amp makes DC or a square wave, whatever you want to call it. People have tested it and found xmax is roughly the same, so the sub would be cooled, though it is getting more total power with a square wave. Note that a very square wave would be amazing distortion and sound really, really bad.


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## lycan

Strictly speaking, there are no DC signals.

Practically speaking, "how long" must a signal remain "stationary" before the system ... _any_ system ... recognizes it as DC?

The answer is this : the signal must remain stationary for a time interval equal to (or greater than) several of the system's slowest, or longest, time constants 

Case in point : if the signal to a driver changes FASTER than the THERMAL time constants of the sub (coil, former, etc.), the signal is NOT equivalent to DC.

Thermal time constants of subs are longer (i suspect) than 25 msec (half of a 20Hz cycle). Therefore, any signal of interest to a sub ... sinewave, clipped sinewave, or squarewave ... will NOT be recognized as DC by the sub.

Bottom line : only two things kill subs : power, or physical abuse. The _shape_ of the signal has nothing to do with it ... only the _power_ of the waveform.


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## MarkZ

sqshoestring, when you see those flat tops, those are not quick flashes of DC. A square wave (note the word "wave") is wholly AC -- no DC component whatsoever. Want to turn a sine wave into a square wave? Add *high frequency* harmonics. High frequencies are not DC.

Why is this important? For four reasons. 

1) the addition of high frequency harmonics, which is what happens when you add sharp discontinuities (like by flattening the top of the wave), can find their way into tweeters ... making clipping dangerous for tweeters on the other side of a passive crossover. Not because of any weird DC argument. But rather, because the power content becomes more concentrated at high frequencies. Note that this has nothing to do with subwoofers though.

2) To suggest that DC is at play here is stupid. When something moves 30, 40, 50 (or more) times per second, it sure as **** ain't standing still! If you had a hot bowl of soup and you moved it back and forth 30 times per second, it would cool off pretty damned quickly!

3) this is related to #2, air movement acts as a lowpass filter. Turn a fan on and off 30 times per second (ignoring electrical lowpass filtering) and it's gonna feel the same as if it was on steadily (minus duty cycle issues). So, if forced air convection is the issue here, and it seems to be, then the lowpass filter action of the air movement itself will smooth these "flat tops".

4) Regarding subwoofers, they will generally not follow the square wave faithfully. Subwoofers act as lowpass filters too. Both mechanically and electrically (this is where inductance comes in). This will have the effect of rounding off those corners. It's safe to say that a subwoofer being fed a 30Hz square wave will NEVER stand still.

Edit: And as lycan describes above, the thermal dissipation itself acts as a lowpass filter. Temperature doesn't change as quickly as the signal itself. The temperature will not change at 30 cycles per second. It acts much slower. It takes time to cool things down and heat them up. Even if the coil were to stand still for ~20ms (25Hz square wave half-period), and then move and stand still, etc, the coil temperature would be unaffected by such brief stand-still times.


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## lycan

at the risk of beating this dog to death ...

it's the very *presence* of this "thermal low-pass filter" that allows us to always consider AVERAGE power in power calculations (where thermal destruction may be possible), rather than PEAK power. And that's why rms voltage, and rms current are valuable : their product gives us AVERAGE power.

When might this be violated? Easy : put a sinewave voltage across a resistor (or sub coil), where instead of a 50msec period ... it has a 50sec period. In this case, you may very well be interested in _peak_ power, rather than _average_ power ... because the signal "changes" slower than the thermal time constants of the system.


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## lycan

Fortunately ... VERY fortunately, in fact ... we find ourselves in a low-pass world


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## MarkZ

lycan said:


> Fortunately ... VERY fortunately, in fact ... we find ourselves in a low-pass world


Except when it comes to our brains and sensory organs, which try to highpass everything.


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## sqshoestring

MarkZ....Yes, yes, yes.....but when a scope shows a flat line, it shows a flat line. How about I play a 1Hz clipped signal to a sub? How long does it have to be flat to be called DC then? If I reverse the polarity once a year is it still AC?

No it does not really matter because power is power, and in the band of frequency humans can hear and the drivers used, it works just as we have explained it over and over in this thread. It does not matter what power is there, it is X amount of current, and either it changes enough to cause cone movement and cool the VC or it does not (in the case of audio in a car it does). So the only difference left is how much power is delivered, and a square wave delivers more than a sine wave up to twice as much. The sub can handle it or it can't. Technically a sine wave should be the most demanding signal an amp or sub ever sees.


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## MarkZ

sqshoestring said:


> MarkZ....Yes, yes, yes.....but when a scope shows a flat line, it shows a flat line. How about I play a 1Hz clipped signal to a sub? How long does it have to be flat to be called DC then? If I reverse the polarity once a year is it still AC?


It depends. Would you call 1Hz "DC"? Because the lowest frequency present in a 1Hz square wave is 1Hz. The square wave will consist of the linear sum of 1Hz, 3Hz, 5Hz, 7Hz, etc waves. So, in effect, when we're comparing the time constant of cooling (as lycan described) and its various mechanisms, the one that's important is the fundamental: 1 Hz. Would I consider 1Hz to be "DC" in this context? Probably not, but we're getting a lot closer than we were at 30Hz!

The point is that anything bouncing back and forth 60 times per second (corresponding to a 30Hz wave) can't possibly stand still long enough for the forced air mechanism to fail. And the square wave would do no worse than the sine wave anyway.



> No it does not really matter because power is power, and in the band of frequency humans can hear and the drivers used, it works just as we have explained it over and over in this thread. It does not matter what power is there, it is X amount of current, and either it changes enough to cause cone movement and cool the VC or it does not (in the case of audio in a car it does). So the only difference left is how much power is delivered, and a square wave delivers more than a sine wave up to twice as much. The sub can handle it or it can't. Technically a sine wave should be the most demanding signal an amp or sub ever sees.


Yup! But let me add one thing. Although a square wave with amplitude A will have more power content than a sine wave with amplitude A, that's not what's at the center of discussion here. When people say that "underpowering is dangerous", the implication is that more power would be less dangerous. So, the comparison shouldn't be between a sine wave of amplitude A and a square wave of amplitude A. The comparison should be between a sine wave of amplitude A, and a sine wave that's had its head cut off... in which case, the clipped signal has _less_ power content than the unclipped one. In that sense, clipping actually serves as a power limiter!


----------



## finkster

I think some of you are missing the point. Giving a sub DC power increases the likelihood of the coil blowing, but not just because it's playing DC. The issue is HEAT.

When subs are rated for rms power, they are taking into consideration that the sub will be moving close to full excursion, which moves and cools the coils (to a point). When you introduce square waves into the picture, the subwoofer isnt moving as proportionally as a clean wave and is receiving more power/movement ratio. 

Really the coils are rated for temperature and not wattage. But telling the consumer, "These coils will work up to 800 degrees and then fail," well how practical is that for the average user?


Here is a real life scenario. Go walk on some HOT sand barefoot. What happens? Well you do the "run for your life" dance" to help cool your feet as much as possible (i.e. keeping your feet away from the sand the longest). Well what happens if you just walked and never ran? You wont be using your feet for a while afterwards. Walking slowly on the hot sand is just like clipping. You arent cooling off your feet (the coil) efficiently enough to prevent damage.

The given rule is that if you FULLY CLIP an amp, it can play up to 1/4 of the sub woofer's rms and never damage the sub. Its not because its DC and its bad for the sub, it's because the wave is square and that means more heat. Heat wise its almost as if the coils are dissipating the same amount of heat as full rms power.


----------



## lycan

finkster said:


> I think some of you are missing the point. Giving a sub DC power increases the likelihood of the coil blowing, but not just because it's playing DC. The issue is HEAT.
> 
> When subs are rated for rms power, they are taking into consideration that the sub will be moving close to full excursion, which moves and cools the coils (to a point). When you introduce square waves into the picture, the subwoofer isnt moving as proportionally as a clean wave and is receiving more power/movement ratio.
> 
> Really the coils are rated for temperature and not wattage. But telling the consumer, "These coils will work up to 800 degrees and then fail," well how practical is that for the average user?
> 
> 
> Here is a real life scenario. Go walk on some HOT sand barefoot. What happens? Well you do the "run for your life" dance" to help cool your feet as much as possible (i.e. keeping your feet away from the sand the longest). Well what happens if you just walked and never ran? You wont be using your feet for a while afterwards. Walking slowly on the hot sand is just like clipping. You arent cooling off your feet (the coil) efficiently enough to prevent damage.
> 
> The given rule is that if you FULLY CLIP an amp, it can play up to 1/4 of the sub woofer's rms and never damage the sub. Its not because its DC and its bad for the sub, it's because the wave is square and that means more heat. Heat wise its almost as if the coils are dissipating the same amount of heat as full rms power.


Nobody's missing the point of "HEAT". In fact, it's all been thoroughly discussed in the series of posts immediately before yours. Please re-read the concepts of _thermal time constants_, what constitutes "DC" for a sub, the cooling effect of a 30Hz square wave, etc.

Already covered.

Power kills subs, not waveform shape. Furthermore, given the thermal behavior of interest (already discussed), it's AVERAGE power that kills subs ... and not PEAK power (there's no such meaningful thing as rms power, so no need to worry about that).


----------



## 89grand

No matter how bad an amp is clipping, I've never seen a speaker just sit still with music or test tones, which is what it would be doing with DC, it also wouldn't be making any sound either because it couldn't if it's not moving. We're talking about mere milliseconds or less that the wave form is flat during hard clipping. 

A test tone at 30hz is moving a speaker 30 times per second. It may sound distorted, but it's still a 30hz tone (with higher frequency harmonics), therefore the speaker is still moving 30 times per second, and even when the wave form is flat, just how long could the speaker be sitting still when it's already moving 30 cycles? If it wasn't, it wouldn't be a 30hz tone anymore. Or no tone at all if the speaker was standing still from DC.


----------



## MarkZ

89grand said:


> No matter how bad an amp is clipping, I've never seen a speaker just sit still with music or test tones, which is what it would be doing with DC, it also wouldn't be making any sound either because it couldn't if it's not moving. We're talking about mere milliseconds or less that the wave form is flat during hard clipping.


Yup. This is why calling the flat tops "DC" is so dangerous and misleading, even aside from the fact that it's technically incorrect. The DC argument relies on the fact that you're defeating the cooling mechanism associated with voice coil movement (this of course isn't the only cooling mechanism, but it can be a significant one for many drivers). This cooling mechanism, specifically, consists of 1) forced air cooling through the pole piece increasing temperature gradients; and 2) extending the effective surface area of the voice coil (moving something back and forth really fast makes it visually appear longer... well, it's similar in the heat domain). But these things aren't problems with a square wave. Why? Because the coil is still moving back and forth dozens of times per second!


----------



## finkster

lycan said:


> Nobody's missing the point of "HEAT". In fact, it's all been thoroughly discussed in the series of posts immediately before yours. Please re-read the concepts of _thermal time constants_, what constitutes "DC" for a sub, the cooling effect of a 30Hz square wave, etc.
> 
> Already covered.
> 
> Power kills subs, not waveform shape. Furthermore, given the thermal behavior of interest (already discussed), it's AVERAGE power that kills subs ... and not PEAK power (there's no such meaningful thing as rms power, so no need to worry about that).


ah im sorry about that. I read the first page only and became discouraged. But I re read the last page and got schooled. Not quite the way I thought about it. Thanks!


----------



## HondAudio

alm001 said:


> NO WAY WOULD 100 WATTS EVER WORK, PUT 500WATTS AND DON'T EVER TURN THE VOLUME DOWN
> 
> MY SPEAKERS NEED 50WATTS, I USED TO HAVE A 49WATT AMP, AND THEY WOULDNT EVEN TURN ON. I GOT A 50W AMP AND NOW THEY ARE AWESOME. CANT TURN IT DOWN THO


I laugh every time I see this


----------



## steffanan

alm001 said:


> NO WAY WOULD 100 WATTS EVER WORK, PUT 500WATTS AND DON'T EVER TURN THE VOLUME DOWN
> 
> MY SPEAKERS NEED 50WATTS, I USED TO HAVE A 49WATT AMP, AND THEY WOULDNT EVEN TURN ON. I GOT A 50W AMP AND NOW THEY ARE AWESOME. CANT TURN IT DOWN THO


hahahaha this guy is so rediculous. also, i think its pretty funny that he thinks he found a 49 watt amp somewhere. as if power handling was that pin-pointed


----------



## Oliver

steffanan said:


> hahahaha this guy is so rediculous. also, i think its pretty funny that he thinks he found a 49 watt amp somewhere. as if power handling was that pin-pointed


Facetious | Define Facetious at Dictionary.com
not meant to be taken seriously or literally: a facetious remark. 2. amusing; humorous. 3. lacking serious intent; concerned with something nonessential

Mebbe night school?


----------



## alm001

Oliver said:


> not meant to be taken seriously or literally: a facetious remark. 2. amusing; humorous. 3. lacking serious intent; concerned with something nonessential


You have defined my entire existence.


Maybe the sarcasm in my post was too thinly veiled.


----------



## sqshoestring

Conversion Table/Decibels-Volts-Watts

lol


----------



## 94VG30DE

alm001 said:


> You have defined my entire existence.
> 
> 
> Maybe the sarcasm in my post was too thinly veiled.


I got it. It's been my sig for a while now...  
-->


----------



## alm001

Yes, I'm quite proud of that. It has actually turned up a lot searching the webs, and I laugh.


----------



## junglejuice72

MarkZ said:


> You can't blow a 500w speaker with 100w of amplification. It's simply not possible, UNLESS the speaker can't truly handle 500w.


You absolutely can destroy a larger powered speaker with a smaller amp, I have done it, it is called clipping.....


----------



## TrickyRicky

Lol @this thread.


----------



## MarkZ

junglejuice72 said:


> You absolutely can destroy a larger powered speaker with a smaller amp, I have done it, it is called clipping.....


Oh for ****'s sake...


----------



## JeremyC

MarkZ said:


> Oh for ****'s sake...


LMAO. 

Mark I can actually see you slapping your forehead on that one. 

If you blew a speaker with a way underpowerd amp, there was probably something wrong with the speaker to start with.


----------



## sqshoestring

Maybe it was VBA.....


:laugh:


----------



## junglejuice72

MarkZ said:


> Oh for ****'s sake...


A Rockford Fosgate Punch 40 powering an Orion XTR15dvc running 2ohm bridged with smoke coming out out of the vent at the rear......


Must have been my imagination 'cause everyone here is obviously an expert.....

Same as blowing tweeters running off 1 Punch 40, replaced them and added a second Punch 40 running 4 ohm bridged instead of 4 ohm stereo, no more blown tweeters, more power (3-4x more), same model tweeters, same crossovers, just lots more power........


----------



## JeremyC

junglejuice72 said:


> A Rockford Fosgate Punch 40 powering an Orion XTR15dvc running 2ohm bridged with smoke coming out out of the vent at the rear......
> 
> Must have been my imagination 'cause everyone here is obviously an expert.....


Yep, there is NO WAY that smoke can come from a mechanical failure inside of a speaker.
Smoke ALWAYS means that you burnt up the voice coil... ;-)

I'm not doubting that you blew your speaker. I'm not doubting that you blew it with a small amp. 

But smoke can be caused by numerous problems. 

95% of the speakers I've blown have been mechanical failures. Anything from the cone separating from the voice coil, the solder point between the leads and the coil coming apart. And those are just the ones I took apart, or took the time to figure out what was wrong. I had others die, some even go up in smoke. But it doesn't mean I fried the coil by running too much power through it. All it means is that something went wrong with the speaker, and caused it to fail.

Unless you took the speaker apart, and inspected it, you can't say exactly what killed it. All you know is that you saw smoke.


----------



## Richv72

This thread I think was the funniest of all time.
http://www.diymobileaudio.com/forum...cussion/109171-would-hurt-do-my-speakers.html


----------



## MarkZ

junglejuice72 said:


> A Rockford Fosgate Punch 40 powering an Orion XTR15dvc running 2ohm bridged with smoke coming out out of the vent at the rear......
> 
> 
> Must have been my imagination 'cause everyone here is obviously an expert.....


No, I'm sure it happened. It just means that either the amp or sub were broken, or the sub couldn't really handle ~200w, or whatever it was you were delivering to it.

This isn't about being an expert. It's about using common sense. Why would you think a sub that's rated to achieve a certain thing, and CAN'T achieve that thing, would be properly rated? It would be like if I said, "yeah, that's a 55 gallon fishtank. Only, you can't put more than 15 gallons of water in it without it overflowing." That sort of no longer makes it a 55 gallon tank, regardless of how badly you want to call it that...


----------



## Richv72

On a cheap amp you can have as much as 3 times the rated power as a clipped signal. So after reading many thing on this topic, I believe you can blow out a subwoofer by using an amp that is not rated as high as the subwoofer rms wise. I also believe its impossible to blow out a sub by underpowering it with a clean signal or even a clipped signal that doesn't exceed the subs rms rating on a meter.


----------



## MarkZ

You're free to believe whatever you like.


----------



## junglejuice72

JeremyC said:


> Yep, there is NO WAY that smoke can come from a mechanical failure inside of a speaker.
> Smoke ALWAYS means that you burnt up the voice coil... ;-)
> 
> I'm not doubting that you blew your speaker. I'm not doubting that you blew it with a small amp.
> 
> But smoke can be caused by numerous problems.
> 
> 95% of the speakers I've blown have been mechanical failures. Anything from the cone separating from the voice coil, the solder point between the leads and the coil coming apart. And those are just the ones I took apart, or took the time to figure out what was wrong. I had others die, some even go up in smoke. But it doesn't mean I fried the coil by running too much power through it. All it means is that something went wrong with the speaker, and caused it to fail.
> 
> Unless you took the speaker apart, and inspected it, you can't say exactly what killed it. All you know is that you saw smoke.


I know that this will be either ignored or I will get flamed but oh well...

I never disassembled the sub because even though a lot of smoke was coming from an Orion "800w" sub it did continue to work, I never claimed it was a mechanical failure but once the smoke comes out it has had a serious degradation electrically.
This occured with a 50hz sinewave being fed to it and was nowhere near the max excursion of the driver so I could easily measure the output of the amp.

The same couldn't be said about the tweeters, as I said same crossovers, same protection system they were toast, but perfectly fine with way more power....

None of this was cheap equipment, all known brands and at least the midrange level of each brand so it was definitely not because of inferior quality components, just too small of an amp trying too hard.

That amp was removed from sub service to run the fronts in bridge mode to compliment the one that blew the tweeters, never had a problem in the years of service following in that configuration, 

more power, 

less to no clipping,

less fried speakers, 

hmm there is a common theme here....

So TrickyRicky, I have no idea why you find this funny

"Lol @this thread."

And MarkZ

A very insightful response 

"Oh for ****'s sake... "

To what I know actually happened, saw it, heard it, smelt it....

JJ


----------



## TrickyRicky

The only sub I ever fried was due to a faulty/bad amplifier (that pinkys @fort worth poorly repaired about ten years ago.

I had about 6 cerwin stroker subs at one point, fed mine 250watts (linear power 2250iq) each.not only was enough power to make them loud but I never needed more power. Keep in mind those subs are [email protected] rms.


----------



## MarkZ

junglejuice72 said:


> And MarkZ
> 
> A very insightful response
> 
> "Oh for ****'s sake... "
> 
> To what I know actually happened, saw it, heard it, smelt it....
> 
> JJ


My "insightful" responses are in the rest of this thread. And if you cared to read the whole thread, you'd discover exactly why your sub (and tweeters) blew. Hint: it wasn't from clipping.


----------



## minbari

junglejuice72 said:


> You absolutely can destroy a larger powered speaker with a smaller amp, I have done it, it is called clipping.....


I go with marks response to this. 

If you have a speaker designed to handle 500watts. if it truely handles 500 watts. then you can fead it straight DC worth of 100watts. it will only heat the coil to 100 watts worth of heat. if the coil handles 500watts, then where is the problem?

BTW, I had a pair of the xtr12" back on the 90's. pretty good subs, but you couldnt power them with 800watts if you tried. the coil might have had a thermal limit of 800 watts, but the mechanical limits were about 3-400 watts on a good day.


----------



## MarkZ

minbari said:


> I go with marks response to this.
> 
> If you have a speaker designed to handle 500watts. if it truely handles 500 watts. then you can fead it straight DC worth of 100watts. it will only heat the coil to 100 watts worth of heat. if the coil handles 500watts, then where is the problem?
> 
> BTW, I had a pair of the xtr12" back on the 90's. pretty good subs, but you couldnt power them with 800watts if you tried. the coil might have had a thermal limit of 800 watts, but the mechanical limits were about 3-400 watts on a good day.


The only caveat there is that DC could disrupt some speakers' ability to remain cool. Speakers are often designed under the assumption that they will be moving when powered. Otherwise, yeah.

I think some confusion comes when manufacturers rate their equipment in terms of "musical power" or some sort of duty cycle-corrected measure. It used to be called "peak power", or something like that, but I get the impression that some manufacturers are leaving that terminology out. And that leads a lot of people to assume that their speakers can take more power than they really can.


----------



## minbari

MarkZ said:


> The only caveat there is that DC could disrupt some speakers' ability to remain cool. Speakers are often designed under the assumption that they will be moving when powered. Otherwise, yeah.
> 
> I think some confusion comes when manufacturers rate their equipment in terms of "musical power" or some sort of duty cycle-corrected measure. It used to be called "peak power", or something like that, but I get the impression that some manufacturers are leaving that terminology out. And that leads a lot of people to assume that their speakers can take more power than they really can.


ya, I thought about it when I said it. but running 1/5 the power shouldnt heat it enough to matter...............now no body runs straight DC, so it is an extreme example, lol.


----------



## hirino

Austin said:


> :laugh::laugh::laugh::laugh:
> 
> So 1 watt made a difference huh? Incredible...



:laugh:


----------



## junglejuice72

minbari said:


> I go with marks response to this.
> 
> If you have a speaker designed to handle 500watts. if it truely handles 500 watts. then you can fead it straight DC worth of 100watts. it will only heat the coil to 100 watts worth of heat. if the coil handles 500watts, then where is the problem?
> 
> BTW, I had a pair of the xtr12" back on the 90's. pretty good subs, but you couldnt power them with 800watts if you tried. the coil might have had a thermal limit of 800 watts, but the mechanical limits were about 3-400 watts on a good day.


A Punch40 on a good day may give if you're lucky around 300w @ 2ohms mono, as I stated before the sub was nowhere near its mechanical limit, ie Xmax but it sure did smell for a while...


----------



## junglejuice72

MarkZ said:


> My "insightful" responses are in the rest of this thread. And if you cared to read the whole thread, you'd discover exactly why your sub (and tweeters) blew. Hint: it wasn't from clipping.


All I know for a fact is that 3-4x more power (from a realistically 40-50wrms to around 100-150wrms) from the same amps running in bridged mode using the same xovers etc resulted in no more blown tweeters.

I also upped the amp on the sub, went from a Punch 40 (250-300w) to a Punch 200 (around 500w) and no more smell from the sub.....

I don't know if it was a characteristic of the amps when pushed hard into a 2ohm mono load or not, I am not an expert, but once these amps were not pushed into clipping and were set up in such a manner that provided more "rated" power I never had an issue with fried drivers again.

I am happy to be corrected but I know what I saw....


----------



## qwertydude

I do know one thing. You can blow a sub with a clean signal at rated power. It just takes more time. I blew out my venerable ID12v3 in a sealed box by playing a clean 250w continuous sine wave at 10 hz for 15 minutes. The really low frequency heats the voice coil and the slow movement lets it build up. I wanted to see just how much heat the ID sub can take. The result is not as much as I thought. I know my old school Rockford Fosgate Punch 12" HX2 could take that kind of punishment all day long and get the magnet so hot you couldn't touch it, but still the voice coil wouldn't burn up.

So yeah you can burn up a sub with less than it's rated for with clean power.


----------



## MarkZ

junglejuice72 said:


> All I know for a fact is that 3-4x more power (from a realistically 40-50wrms to around 100-150wrms) from the same amps running in bridged mode using the same xovers etc resulted in no more blown tweeters.
> 
> I also upped the amp on the sub, went from a Punch 40 (250-300w) to a Punch 200 (around 500w) and no more smell from the sub.....
> 
> I don't know if it was a characteristic of the amps when pushed hard into a 2ohm mono load or not, I am not an expert, but once these amps were not pushed into clipping and were set up in such a manner that provided more "rated" power I never had an issue with fried drivers again.
> 
> I am happy to be corrected but I know what I saw....



You didn't "see" anything, though. It's not like you systematically introduced clipping, keeping all other variables the same, and discovered your speaker blown. It's not like you took a spectrum analyzer out to your car and measured the power content within the passband of your sub when it blew.

You're correlating two observations -- 1) you used an amp with a low power rating and blew your sub; and 2) you used a different amp with a high power rating and didn't blow a different sub (yet). You're then concluding that the difference is the power rating of the amp. This is like doing a dance out in the field and then, after it starts raining, concluding that dancing makes it rain.

I asked six times in this thread for someone to describe, mechanistically, what it is about clipping that blows subwoofers. Nobody -- not a single person -- has ventured to answer this question.


----------



## qwertydude

Why is clipping dangerous? I'm surprised no one answered that. You can kinda reference it with how I blew my ID12v3 with 10hz.

Power generates heat, heat is removed from the voice coil mostly with air movement caused by the back and forth motion of the voice coil and speaker assembly. The more movement, the more cooling.

So a clipped signal in effect is like an ultra low frequency (0 hz) signal. IE no speaker movement during the clipped section. So during that clipped moment cooling doesn't occur and heat builds up. Do this enough times and for long enough and the temperature will keep climbing eventually burning the woofer up.

Now when this occurs is debatable. Because some woofers are better at cooling than others. But the fact is if the thermal limit of the subwoofer is 250 watts, and you feed a 250 watt signal with clipping you'll definitely be over the thermal limit of the woofer.

Here's an experiment to try. Get a cheapy woofer, around 40 watts. Put it in a box and get your multimeter. Feed a 12 volt AC sine wave into it from your amplifier. This is 36 watts of power. The woofer should be able to play all day long. Now instead, get a 12v DC power supply and hook it to the speaker terminal and see how long it lasts before the coil cooks. You can play a continuous low frequency so it's not a an annoying noisemaker, hence why my tests are at 10 hz. 

That's essentially what you're doing with a clipped signal. The flat portion of the clipped signal acts as DC current. That means during that flat signal there's no woofer movement and heat builds up.

Another experiment to try is get a cheap woofer and feed it a square wave signal. It'll burn up a lot quicker than a sine wave of equivalent power. I did this using a signal generator hooked up to my amplifier. It's noisy as hell and sounds distorted but I made sure I wasn't clipping the amp by making the output voltage less than the maximum amp voltage so clean, but still a signal resembling a heavily clipped signal. Results; burned woofer.

Basically if you're feeding power to the woofer and it isn't moving because the signal is flat you'll build up more heat than feeding the same power and making sure it's moving. Build up enough heat and the voice coil fries.

Hope that answers your question.


----------



## cmayo117

qwertydude said:


> Why is clipping dangerous? I'm surprised no one answered that. You can kinda reference it with how I blew my ID12v3 with 10hz.
> 
> Power generates heat, heat is removed from the voice coil mostly with air movement caused by the back and forth motion of the voice coil and speaker assembly. The more movement, the more cooling.
> 
> So a clipped signal in effect is like an ultra low frequency (0 hz) signal. IE no speaker movement during the clipped section. So during that clipped moment cooling doesn't occur and heat builds up. Do this enough times and for long enough and the temperature will keep climbing eventually burning the woofer up.
> 
> Now when this occurs is debatable. Because some woofers are better at cooling than others. But the fact is if the thermal limit of the subwoofer is 250 watts, and you feed a 250 watt signal with clipping you'll definitely be over the thermal limit of the woofer.
> 
> Here's an experiment to try. Get a cheapy woofer, around 40 watts. Put it in a box and get your multimeter. Feed a 12 volt AC sine wave into it from your amplifier. This is 36 watts of power. The woofer should be able to play all day long. Now instead, get a 12v DC power supply and hook it to the speaker terminal and see how long it lasts before the coil cooks. You can play a continuous low frequency so it's not a an annoying noisemaker, hence why my tests are at 10 hz.
> 
> That's essentially what you're doing with a clipped signal. The flat portion of the clipped signal acts as DC current. That means during that flat signal there's no woofer movement and heat builds up.
> 
> Another experiment to try is get a cheap woofer and feed it a square wave signal. It'll burn up a lot quicker than a sine wave of equivalent power. I did this using a signal generator hooked up to my amplifier. It's noisy as hell and sounds distorted but I made sure I wasn't clipping the amp by making the output voltage less than the maximum amp voltage so clean, but still a signal resembling a heavily clipped signal. Results; burned woofer.
> 
> Basically if you're feeding power to the woofer and it isn't moving because the signal is flat you'll build up more heat than feeding the same power and making sure it's moving. Build up enough heat and the voice coil fries.
> 
> Hope that answers your question.


A clipped sine wave is not DC. The voltage is still alternating and it's still AC. And the cone is still moving just as much. If it wasn't, it wouldn't make any sound. Even if you sent a perfect 10Hz square wave to a speaker with no inductance, neither of which exist, the cone would only be standing still for .05 seconds between each instant switch in current direction. And in the real world, the current can't actually switch directions instantly because of inductance and capacitance. So, where exactly is all this time where the coil is just sitting still and building up heat? 

Also, the speaker doesn't have to move to keep the coil cool. If the coil is hotter than the surrounding environment, some heat is going to be conducted away from it. As long as the coil isn't dissipating too much power, it's not going to burn up. 

MarkZ is right, and these points have already been made multiple times in this thread and in many others on this site. It is obvious from your posts that you do not understand a lot about physics, so I would suggest going back and reading this thread before posting again.


----------



## qwertydude

I didn't say a clipped sine wave is DC look carefully at what I typed. The flat portion of the sine wave acts like DC on a coil which represents more built up heat in the coil.

And if you know how they calculate the thermal limits of a subwoofer you'll know they do it with sine waves which keeps the woofer moving. I realize that even sitting still the voice coil will still be cooled somewhat by air conduction. But open up a physics text book before opening your mouth. I took numerous thermodynamics and heat transfer courses when I was in the navy doing nuclear engineering.

You see the problem is with fluid cooling, air is considered a fluid in engineering, you can only get so much cooling relative to fluid speed. This is why we don't run ridiculously fast fluid cooling flow rates in nuclear reactors, at high temperatures you only get so much cooling, after a certain amount increasing coolant speed won't increase cooling capacity. What does this have to do with voice coils? A lot.

What this means is with a square wave the transition from one polarity DC to another is basically as fast as the woofer can respond. This means extremely high velocity. This high velocity for a short amount of time doesn't cool as well as a slower velocity for a longer amount of time. Why? I'll explain a little later but have to address your erroneous belief that passive cooling of the coil while stationary is a significant factor. It simply isn't.

And no the simple air conduction doesn't wick away enough heat to lower the temperature. If it did convective currents would be able to cool our nuclear reactors, and heck your computer wouldn't need cooling fans. Fact is the voice coils need forced air cooling and their relatively low thermal capacity due to being made light weight means they build up heat pretty fast. So the quick transition from one polarity to another means less average cooling time. Add that in addition to the lack of movement in between cycles due to clipped or square signals and things just go downhill from there.

Forced convection - Wikipedia, the free encyclopedia

Read it, then look at the Archimedes equation. You'll see that at the transition from simple convection to forced air convection, Grashof number (simple convection) compared to Reynold's number (forced air) you'll see that because Reynold's number is squared it quickly takes over from regular convection. Now where this falls apart though is that Reynold's number only applies to fluids of constant volume and density. This is where the subwoofer speed starts affecting cooling at those high transition speeds you don't get ideal fluid flow. You actually lower the density of the air because the air can't flow past the narrow magnetic gap very fast. Lower density means lower cooling. Hence why square waves are so thermally damaging. What this means is if you have 4 times the air velocity you get 16 times the cooling capability, so a voice coil simply can not cool itself due to natural convection. It simply wasn't designed for it.

A square wave of equivalent power will punish your speakers. If you ever experimented with it you'll find it destroys tweeters and mids because the transients create really high reactive power spikes in the cross over networks. They punish woofers because they keep the woofers out of continuous motion which heats them up really quick, not to mention all the thermodynamics I mentioned above.

So let me tell you, when have you last opened a physics and engineering textbook?


----------



## junglejuice72

MarkZ said:


> 2) you used a different amp with a high power rating and didn't blow a different sub (yet). You're then concluding that the difference is the power rating of the amp.


Same sub, different amp.

And of course same amps bridged with replacement (same model) tweeters.

I am not professing to know what the theory is but what I do know is that a larger, more powerful amp on the SAME sub that let the smoke out never had another problem.

AND the same small amps reconfigured to run 4 ohm mono to my splits (3-4x more power then before) resulted in no more blown tweeters....

I don't know how else to put it......


----------



## JeremyC

junglejuice72 said:


> Same sub, different amp.





junglejuice72 said:


> I also upped the amp on the sub, went from a Punch 40 (250-300w) to a Punch 200 (around 500w) and no more smell from the sub.....


That doesn't sound like a fried coil. If you saw that much smoke, and it came from the coil, continuing to use the sub would have caused more problems. 

It sounds like there was something on the coil from the build process that shouldn't have been there. 

You ran the sub, burnt off the material (saw the smoke), and thought you screwed up the coil. 

But then you gave it more power and it kept working.


----------



## hirino

qwertydude said:


> I do know one thing. You can blow a sub with a clean signal at rated power. It just takes more time. I blew out my venerable ID12v3 in a sealed box by playing a clean 250w continuous sine wave at 10 hz for 15 minutes. The really low frequency heats the voice coil and the slow movement lets it build up. I wanted to see just how much heat the ID sub can take. The result is not as much as I thought. I know my old school Rockford Fosgate Punch 12" HX2 could take that kind of punishment all day long and get the magnet so hot you couldn't touch it, but still the voice coil wouldn't burn up.
> 
> So yeah you can burn up a sub with less than it's rated for with clean power.


i agree with what you said but who plays sin waves for 15 minutes?


----------



## MarkZ

qwertydude said:


> Why is clipping dangerous? I'm surprised no one answered that. You can kinda reference it with how I blew my ID12v3 with 10hz.
> 
> Power generates heat, heat is removed from the voice coil mostly with air movement caused by the back and forth motion of the voice coil and speaker assembly. The more movement, the more cooling.
> 
> So a clipped signal in effect is like an ultra low frequency (0 hz) signal.


_Please_ read the thread. Lycan and I already demonstrated that this is NOT the case. IIRC, somewhere between post 80 and post 90 you'll find a few posts that deal directly with this.

Edit: Specifically, read posts 81, 82, 83, 87, and 89.


----------



## cmayo117

qwertydude said:


> I didn't say a clipped sine wave is DC look carefully at what I typed. The flat portion of the sine wave acts like DC on a coil which represents more built up heat in the coil.
> 
> And if you know how they calculate the thermal limits of a subwoofer you'll know they do it with sine waves which keeps the woofer moving. I realize that even sitting still the voice coil will still be cooled somewhat by air conduction. But open up a physics text book before opening your mouth. I took numerous thermodynamics and heat transfer courses when I was in the navy doing nuclear engineering.
> 
> You see the problem is with fluid cooling, air is considered a fluid in engineering, you can only get so much cooling relative to fluid speed. This is why we don't run ridiculously fast fluid cooling flow rates in nuclear reactors, at high temperatures you only get so much cooling, after a certain amount increasing coolant speed won't increase cooling capacity. What does this have to do with voice coils? A lot.
> 
> What this means is with a square wave the transition from one polarity DC to another is basically as fast as the woofer can respond. This means extremely high velocity. This high velocity for a short amount of time doesn't cool as well as a slower velocity for a longer amount of time. Why? I'll explain a little later but have to address your erroneous belief that passive cooling of the coil while stationary is a significant factor. It simply isn't.
> 
> And no the simple air conduction doesn't wick away enough heat to lower the temperature. If it did convective currents would be able to cool our nuclear reactors, and heck your computer wouldn't need cooling fans. Fact is the voice coils need forced air cooling and their relatively low thermal capacity due to being made light weight means they build up heat pretty fast. So the quick transition from one polarity to another means less average cooling time. Add that in addition to the lack of movement in between cycles due to clipped or square signals and things just go downhill from there.
> 
> Forced convection - Wikipedia, the free encyclopedia
> 
> Read it, then look at the Archimedes equation. You'll see that at the transition from simple convection to forced air convection, Grashof number (simple convection) compared to Reynold's number (forced air) you'll see that because Reynold's number is squared it quickly takes over from regular convection. Now where this falls apart though is that Reynold's number only applies to fluids of constant volume and density. This is where the subwoofer speed starts affecting cooling at those high transition speeds you don't get ideal fluid flow. You actually lower the density of the air because the air can't flow past the narrow magnetic gap very fast. Lower density means lower cooling. Hence why square waves are so thermally damaging. What this means is if you have 4 times the air velocity you get 16 times the cooling capability, so a voice coil simply can not cool itself due to natural convection. It simply wasn't designed for it.
> 
> A square wave of equivalent power will punish your speakers. If you ever experimented with it you'll find it destroys tweeters and mids because the transients create really high reactive power spikes in the cross over networks. They punish woofers because they keep the woofers out of continuous motion which heats them up really quick, not to mention all the thermodynamics I mentioned above.
> 
> So let me tell you, when have you last opened a physics and engineering textbook?


Whether or not the coil can stay cool depends on how much power is dissipated. Not all computers have cooling fans. Ever heard of a passive heat sink? Nuclear reactors are dealing with a lot more energy than a speaker, and their entire purpose is to transfer as much heat to electricity as possible, so it's not a good example IMHO. 

I agree that the coil will cool faster with air being forced across it, but that will not matter if the coil can handle the heat dissipation without forced air. And I'm still skeptical that a clipped wave will result in significantly less cooling than a sine wave. Yes in a perfect world a square wave would try to make the cone move at infinite velocity, but in the real world inductance means that the current can't change direction that fast. Also, the maximum velocity of the cone is still very high in a sine wave. And I could be wrong, but I would think forcing air through a tight space would increase the pressure, and therefore density, of the air in the gap, not decrease it. 

And to answer your question, the last time I opened a physics textbook was last night. I'm a college student and have taken plenty of physics courses. However, I have not yet taken any upper level thermodynamics courses and I don't pretend to be an expert. I wasn't trying to start a pissing match or anything. Your comparison of clipped AC to DC just made me think you were making the same ridiculous clipped AC is DC argument.


----------



## qwertydude

You've never heard of Bernoulli's principle have you? The faster the air velocity, the lower the air pressure. It's real, the lower the air pressure the lower the density of the air and the less cooling you have.

Regardless of power heat transfer is the same. Engineering is engineering. I have heard of passively cooled computers. Do you know how they're designed? I do. Their heat sinks need to have very widely spaced fins and surface area needs to be vastly more than forced air, more than 10 times as much because convection cools very little. Usually in those cases passively cooled computers use under-clocked lower performance processors to minimize heat. If you want a similar situation in our reactors. We can actually cool them with natural convection. The only time we rely on that is emergencies after the shut down and forced cooling and after decay heat has reduced heat output 95% yeah that 20 times less heat output that natural convective cooling is capable of. See thermodynamics, is still thermodynamics. Physics works on a 250 watt voice coil and a 25 megawatt nuclear reactor. Amazing!

The equations are the same. In fact because in physics you're usually using ideal fluids, in the real world cooling is usually less than what the ideal equations would imply, therefore most thermal and cooling capacities end up being derated because cooling ends up being less than what the general equations show.


----------



## MarkZ

qwertydude said:


> You've never heard of Bernoulli's principle have you? The faster the air velocity, the lower the air pressure. It's real, the lower the air pressure the lower the density of the air and the less cooling you have.
> 
> Regardless of power heat transfer is the same. Engineering is engineering. I have heard of passively cooled computers. Do you know how they're designed? I do. Their heat sinks need to have very widely spaced fins and surface area needs to be vastly more than forced air, more than 10 times as much because convection cools very little. Usually in those cases passively cooled computers use under-clocked lower performance processors to minimize heat. If you want a similar situation in our reactors. We can actually cool them with natural convection. The only time we rely on that is emergencies after the shut down and forced cooling and after decay heat has reduced heat output 95% yeah that 20 times less heat output that natural convective cooling is capable of. See thermodynamics, is still thermodynamics. Physics works on a 250 watt voice coil and a 25 megawatt nuclear reactor. Amazing!
> 
> The equations are the same. In fact because in physics you're usually using ideal fluids, in the real world cooling is usually less than what the ideal equations would imply, therefore most thermal and cooling capacities end up being derated because cooling ends up being less than what the general equations show.


All of this is irrelevant, because
1) the subwoofer never stops moving -- "flat tops" are lowpass filtered electrically and mechanically
2) even if the sub could faithfully reproduce "flat tops", moving back and forth dozens of times per second is too fast for heat to build up (see lycan's post)

In fact, one could argue that coil motion resembling square waves actually improves heat dissipation in extended pole piece designs, because the spatial distribution of coil position is more uniform and less gaussian-like.

This was all explained earlier in this thread.


----------



## qwertydude

A lot of class A/B amps don't have subsonic filters. I know for a fact that amps I've owned could actually reproduce 1 hz at maximum power, I tested this with a signal generator. This was Sony Xplods, Pioneer amps, Boss, Kenwoods, Profile back in the day. That means the flats were reproduced at the speaker level. In fact I just ran a little experiment. My cheapy Boss AR1500M can hold a reasonable square wave down to about .5 hz at maximum power That's a heck of a lot of very little speaker movement and a whole heck of a lot of power going into the woofer.

There's no mechanical filtering for DC in a speaker, please, put DC current in a speaker you'll see they pop out and stay out. So mechanical filtering is out of the question, and if an amp can move a speaker at 1 Hz there's no reason why at clipping it wouldn't hold the speaker still.

If you want proof I can post a video of a 1 hz square wave and you'll see the woofer literally getting held out in place by the amp.

Also one thing about square waves is the leading and trailing edges being at such steep transitions, forces a lot of back emf that the amp has to absorb and the amp being far less in impedance than the speakers to promote damping ends up dissipating the back emf in the coil creating further heat. The dissipation of back emf sends high power pulses back and forthin the coil that heats up the voice coils due to I^2*R losses. This in electrical engineering theory is known as reactive power, it's a real problem in power systems and especially more so in purely inductive and purely capacitive systems. So in reality if the measured AC voltage looks like you're dissipating 100 watts, in reality due to inductive reactance, the power factor could be making the real power in the circuit read something like 150 watts.

That's also one reason why square wave don't play well in 120v power systems like those 12v to 120v inverters. It's because a modified sine wave doesn't play well with motors (inductive load) efficiency is reduced 20% due to reactive power increasing the heat in the motor for the same amount of work done. A square wave can reduce this efficiency down to 50% further increasing heat a tremendous amount. Imagine 50% more heat for the same amount of work. That's what a lot of lay people don't understand about power factor. And power factor has a lot to do with clipped signals, and square waves.

http://en.wikipedia.org/wiki/Power_inverter#Square_wave
http://www.rpc.com.au/pdf/sine_&_square_wave_electricity.pdf

The second paper doesn't explain it as well, but it's touching on the theories that square waves in inductive loads create more heat. This is due to the decrease in power factor which increases currents traveling back and forth between supply (amp) and inductive load (speaker coil). And this doesn't even cover the fact that with square waves and clipped signal you get less cooling due to the reduced constant motion and very high speed transitions. It all adds up to the facts, clipped signals of the same apparent power do heat woofers more than clean signals.

http://en.wikipedia.org/wiki/AC_power#Real.2C_reactive.2C_and_apparent_powers

This is the problem with society. People who aren't engineers think they can out engineer the engineers without even understanding the basic aspects of engineering. So if you want to prove me wrong please post hard engineering and reference. Those articles are only the beginning of the lessons you need to learn before posting how amplifiers and power systems work. Otherwise I'll continue believing what I've learned in engineering school. Not only that but I have done experiments with woofers and square waves and they do burn out faster.


----------



## left channel

Really? Go find me some music that has a sustained 1hz. Now you're just arguing for the sake of arguing.



qwertydude said:


> A lot of class A/B amps don't have subsonic filters. I know for a fact that amps I've owned could actually reproduce 1 hz at maximum power, I tested this with a signal generator. This was Sony Xplods, Pioneer amps, Boss, Kenwoods, Profile back in the day. That means the flats were reproduced at the speaker level.
> 
> There's no mechanical filtering for DC in a speaker, please, put DC current in a speaker you'll see they pop out and stay out. So mechanical filtering is out of the question, and if an amp can move a speaker at 1 Hz there's no reason why at clipping it wouldn't hold the speaker still.
> 
> If you want proof I can post a video of a 1 hz square wave and you'll see the woofer literally getting held out in place by the amp.


----------



## JeremyC

qwertydude said:


> So mechanical filtering is out of the question, and if an amp can move a speaker at 1 Hz there's no reason why at clipping it wouldn't hold the speaker still.
> 
> If you want proof I can post a video of a 1 hz square wave and you'll see the woofer literally getting held out in place by the amp.


Ok, so tell me one song that has a 1hz tone. 

After all, we are talking about music, and clipping a standard musical sine wave. 

They really did touch on all of this earlier in the thread. At 20hz, the bottom of our musical spectrum, the sub is still moving way more than most people realize. And it is moving enough to keep it cool, especially with an amp rated below its RMS. 

And that’s a 20hz test tone. An extreme example when compared to a wave carrying data for 20 to 80hz, along with the standard dynamics of music.


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## JeremyC

left channel said:


> Really? Go find me some music that has a sustained 1hz.


LMAO... You beat me to it.


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## qwertydude

One could argue that coil motion resembling square waves actually improves heat dissipation, but one would be wrong. The further I have to explain this the more is lost to the general population and it seems the more they disbelieve the engineering. I suppose it's just that hard to accept that others may be smarter than you and may just have done the actual engineering, and have more experience than you. Just because I don't have lots of posts doesn't mean I'm not a qualified electronics engineer with a lot of thermodynamics experience to boot from my nuclear engineering days.

Tell me what qualifications do you posses that make you an expert on engineering?

Because it's not just about 1 hz. Try not to distract by taking just one aspect of my argument. I'm using the 1 hz as proof that A/B amps can produce pretty much perfectly flat square waves which another poster was claiming was impossible because they're somehow mechanically or electrically filtered by the amplifier or sub, which they're not. The proof that they're not is the fact that the amp can produce a 1 hz square wave.

And for me to prove the power factor of square waves would require far more explanation than I care to post on this site. It's not your job to be an engineer but it would be nice if you can at least partially believe what the engineers are trying to explain.


----------



## JeremyC

I'm not trying to take away from your argument, by focusing on 1hz.

But I will ask you this. 

In a musical application, where the freq range and dynamics of music come into play. How would a clipped wave, cause an amp to overheat a voice coil thats rating was above the RMS output of the amp?


----------



## cmayo117

qwertydude said:


> One could argue that coil motion resembling square waves actually improves heat dissipation, but one would be wrong. The further I have to explain this the more is lost to the general population and it seems the more they disbelieve the engineering. I suppose it's just that hard to accept that others may be smarter than you and may just have done the actual engineering, and have more experience than you. Just because I don't have lots of posts doesn't mean I'm not a qualified electronics engineer with a lot of thermodynamics experience to boot from my nuclear engineering days.
> 
> Tell me what qualifications do you posses that make you an expert on engineering?
> 
> Because it's not just about 1 hz. Try not to distract by taking just one aspect of my argument. I'm using the 1 hz as proof that A/B amps can produce pretty much perfectly flat square waves which another poster was claiming was impossible because they're somehow mechanically or electrically filtered by the amplifier or sub, which they're not. The proof that they're not is the fact that the amp can produce a 1 hz square wave.
> 
> And for me to prove the power factor of square waves would require far more explanation than I care to post on this site. It's not your job to be an engineer but it would be nice if you can at least partially believe what the engineers are trying to explain.


It's not about proving who's smarter. It's just that this topic has been discussed endlessly and it was pretty much accepted that clipping isn't hard on subwoofers. The only exception from what I understood is that the average power of a heavily clipped sine wave is larger than that of a normal sine wave with the same maximum voltage. However, any new insight is welcome, and your the first person I've heard make an argument based on any real physics that clipping could disrupt the cooling of a speaker. I'm still not totally convinced that what you're describing will make a large enough difference in this situation to really be significant. But like I said, I'm no expert on thermodynamics or engineering.


----------



## qwertydude

Yes but have you considered that a clipped signal also increases the real power of the inductive system causing even more heating due to currents flowing back and forth between the power source and coils?

It's this principle of real vs apparent power that's difficult for many lay people to grasp. It's why motor efficiency goes way down and motors get really hot if you try to feed them with square waves and or even the stepped waves of solid state inverters. A voice coil is pretty much just a motor so it follows they'll also suffer from increased heating due to increases in real power if fed with flat topped or square wave signals.

This isn't make believe, it happens. Try running a fridge on the square waves of an inverter. You're still feeding the same equivalent apparent power but the real power in the circuit is much higher leading to increased temps. You'll burn the motor up, it's those pesky flat portions and steep steps of the wave are what's responsible. Same with clipped signals or square waves and woofers.

So you may be measuring 100 watts at the speaker terminals but with non-sine wave waveforms going through an inductor you may very well have 150 watts actually flowing through those wires dissipating that much more heat.


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## MarkZ

qwertydude said:


> This is the problem with society. People who aren't engineers think they can out engineer the engineers without even understanding the basic aspects of engineering. So if you want to prove me wrong please post hard engineering and reference.


You should delete this post, because it's embarrassing. You think you're the only engineer in this forum, yet you don't grasp Fourier analysis or lowpass filtering. :laugh: Let me address your two errors.

First, you come up with some 1Hz nonsense. I think you believe that by clipping a 20Hz waveform (for example), you introduce low frequency components. Clipping is a symmetric property, and so it's well-described by Fourier analysis. You can model the resultant waveform in a pretty computationally-intensive way, but it's much easier to analyze what a square wave with fundamental f1 looks like.

square wave = sum(A/N*fN) = A0*f1 + A0/3*f3 + A0/5*f5 + ...

In other words, a square wave is composed of odd-order harmonics that are integer multiples of the fundamental. You can read more about it on wikipedia, paying careful attention to the first equation (which is the one above).

In basic terms, clipping a waveform will NEVER introduce frequencies lower than the fundamental. As an engineer, this should be obvious to you.

Second, when I said "lowpass", I meant lowpass, and not highpass. Lowpass means that high frequencies are filtered. It does not mean that DC is filtered. I'll assume you know this and that you made an error. Given your obvious error, I'll also assume that you'll retract your post where you claimed I was trying to tell you that a speaker would not reproduce DC.

Thanks for listening.

-Mark Z
engineer


----------



## 94VG30DE

qwertydude said:


> ...


The reason we know you are an engineering student is the condescending tone and know-it-all attitude. By all means, continue to argue semantics based on physics without thermo, covering information that's already been addressed, all while blatantly ignoring real-world use case. To ensure you continue to be God's gift to the world, make certain that you carry this attitude into your first engineering position. You'll do great.


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## JeremyC

I understand all of that. Its all about average power over a given amount of time. 

When you clip the top off of an AC signal, the average power goes up. 

If music was a simple 20hz tone, and you clipped the top off of the wave, yes your average power could go up a lot over x amount of time. 

It all depends on how much of the wave your clipping. But even then, your limited by the output capabilities of the amp. If the amp is rated at 500 watts, and you clip 10% off of the wave, your average power would only go up by X amount. 

And thats with a sine wave, not music.

When you take into consideration the dynamics of music, your average power drops, and its still limited by the output stage of the amp. 

So yes, the coil will see more power and get hotter. But the chances of reaching the thermal rating of the coil, with an amp thats smaller than the rating of the sub, is really slim. 

I will be honest dude. I don't have all the fancy degree's that you do, but my background is avionics and electronics. 

I used to think the same thing you do. But I was focused on the numbers, and wasn't taking everything into consideration. 

I actually had someone way smarter than I am, explain it in a way it clicked and I realized I was wrong.

Thank you google search, and BCAE.com. I found a picture that might help.


----------



## qwertydude

It's not about frequency response. My 1 Hz example is to address the claim saying that an amplifier or speaker magically removes the squared of component portion of the wave. It doesn't it only softens the transition somewhat, but the clipped signal still settles into a portion of DC. How much do you have to try to parse this argument til you can somehow do backflips to try to prove a faulty electrical engineering theory?

Mathematically MarkZ you are correct. But do you know how it applies in the real world?

I'm still left wondering how you claim that the flats are somehow electrically and mechanically filtered so the subwoofer is moving during a portion of flat wave. If a subwoofer can't reproduce the effectively low frequencies, and a flat portion of a waveform is essentially low frequencies, it's not really doing it's job as a subwoofer. A differential equation proves flat portions of the wave form is essentially 0 hz, that's the point I was trying to get at. That A/B amps will produce square waves just fine and speakers will reproduce them accurate enough to cause excess heating.

I NEVER SAID SQUARE WAVES INTRODUCE LOW FREQUENCY. STOP PUTTING WORDS IN MY MOUTH!

Do a mathematical analysis on an extremely clipped waveform, frequency irrelelvant it will always resemble a square wave, and you'll see it closely resembles a square wave, nowhere nowhere nowhere nowhere did I ever say it was equivalent to low frequencies.

What I'm saying is amplifiers are fully capable of producing square waves and clipped signals very closely resemble square waves. And with that square waves increase the apparent power in an inductive system higher than the real measured power indicates, this creates more heat.

And if you can provide just one reference that, in an inductive circuit, square waves of the same measured power as sine waves don't have more apparent power I'll retract everything I've said. It's that apparent power that serves to further heat the coil more than you'd expect.

All I'm saying is I've done this experiment before, I've run sine waves through a cheap subwoofer for hours and it held up, but put a square wave of equivalent measured rms power and it'll fry.


----------



## MarkZ

JeremyC said:


> I understand all of that. Its all about average power over a given amount of time.
> 
> When you clip the top off of an AC signal, the average power goes up.


You're overthinking things. If you chop the tops of the waveform off, you DECREASE the power content of the waveform. This is in comparison to the unclipped version of the _same_ waveform. If you're familiar with calculus, what you're doing is integrating the square of each waveform, which should make this relationship obvious.

When you also consider that the impedance of the subwoofer is often higher at higher frequencies, you get an even further reduction in power due to clipping.

This is why I said earlier in the thread: clipping is an (ugly) limiter. 

PS - I strongly suggest everyone reread the thread. All this ****'s been hashed out months ago. We shouldn't be reinventing the wheel here...


----------



## MarkZ

qwertydude said:


> It's not about frequency response. My 1 Hz example is to address the claim saying that an amplifier or speaker magically removes the squared of component portion of the wave. It doesn't it only softens the transition somewhat, but the clipped signal still settles into a portion of DC. How much do you have to try to parse this argument til you can somehow do backflips to try to prove a faulty electrical engineering theory?


You brought up 1Hz to try to sustain your DC argument, but as others have attempted to explain to you, clipping a 20-20k signal will NEVER introduce anything approaching DC. If the lowest frequency in your signal is 20Hz, you will NEVER achieve 19Hz, let alone 1Hz. I explained pretty clearly why the subwoofer will NEVER stop moving, and why clipping does not mimic DC. So, as much as you whine about me putting words in your mouth, let me remind you that you're the only one who's brought up this DC nonsense. So yes, if you want to drop the DC rubbish, I'm more than happy to see you do so.




> What I'm saying is amplifiers are fully capable of producing square waves and clipped signals very closely resemble square waves. And with that square waves increase the apparent power in an inductive system higher than the real measured power indicates, this creates more heat.


Your first sentence is correct, your second sentence isn't. You're neglecting the fact that what turns a sine wave into a square wave is the introduction of high frequency harmonics. The inductance of the coil, and the mechanical properties of the subwoofer, make it behave like a lowpass filter. As a result, the motion of the subwoofer ends up resembling a "rounded" version of the input square wave. That's what lowpassing a square wave _does_.

As for power, _of course_ a square wave of amplitude A has more power content than a sine wave of amplitude A! _But that doesn't really tell us anything._ All that says is that power increases when you turn the volume knob up, even once the amp is saturated. [this is true, but it's also worth pointing out that power no longer increases with the square of A... after clipping, it begins looking more logarithmic] The comparison that we really care about is between the waveform of amplitude A clipped vs. the waveform of amplitude A unclipped. This is because the discussion is about clipping, not a psychological evaluation of stereo owners' use of the volume knob.


----------



## MarkZ

qwertydude said:


> All I'm saying is I've done this experiment before, I've run sine waves through a cheap subwoofer for hours and it held up, but put a square wave of equivalent measured rms power and it'll fry.


I'm calling ********. You've never done this and you know it.


----------



## JeremyC

MarkZ said:


> You're overthinking things. If you chop the tops of the waveform off, you DECREASE the power content of the waveform. This is in comparison to the unclipped version of the _same_ waveform. If you're familiar with calculus, what you're doing is integrating the square of each waveform, which should make this relationship obvious.


Mark I take back everyting I said in my pm ;-) 

Nah, it makes sence. I miss read something on BCAE. But everything is clicking now. 

FYI, I suck at Calculus. 

But if you can explain it in a way I can see it, things tend to click really quickly.

For those of us that aren't rocket scientist. This is a great little write up explaining what these guys are talking about. Don't feel bad if you have to read it a couple times. I had to. 

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


----------



## MarkZ

JeremyC said:


> Mark I take back everyting I said in my pm ;-)
> 
> Nah, it makes sence. I miss read something on BCAE. But everything is clicking now.
> 
> FYI, I suck at Calculus.
> 
> But if you can explain it in a way I can see it, things tend to click really quickly.
> 
> For those of us that aren't rocket scientist. This is a great little write up explaining what these guys are talking about. Don't feel bad if you have to read it a couple times. I had to.
> 
> Why Too Little Power will NOT blow Your Speakers



Just to clarify (maybe Perry did it in his site...), you can calculate the power content of a waveform by adding up the area under the curve (ok, first you have to square it, but nevermind that for now). As you can see from the first figure on that site, there's more area under the sine wave than the clipped sine wave. That's all I was trying to say in my response to you.

If you look at the second figure, they replace a clipped sine with a square wave. A square wave can be used to approximate a severely clipped sine wave. The square wave has more energy, but this is due to the fact that they increased the amplitude of the (clipped) sine wave to achieve this square wave. By a lot. My point to qwertydude was that an apples-to-apples comparison is two equivalent sine waves, one clipped and one not (Fig 1). THAT'S what the discussion is about -- whether clipping hurts speakers, not whether idiots and their volume knobs hurt speakers.


----------



## qwertydude

I'll post a video. I have a spare bookshelf speaker lying around and will reproduce this experiment as stated. Continuous sine wave power in a woofer vs continuous square wave power in a woofer.

The experiment will be as follows. My computer will act as a signal generator I will produce sine wave and square waves. I will use my Boss AR1500M amp powered by a regulated 13.8 volt pwoer supply. I will use 20 hz as the example frequency unless the woofer is exceeding mechanical capabilities before reaching thermal capabilities. I won't exceed the power limits of the woofer so that in sine wave you can see it would run indefinitely. I will then without changing output settings of frequency or amplitude switch over to square wave and you'll see it will burn out.

If I post this video and prove square waves can burn out a subwoofer vs the equivalent sine wave. Will you post a retraction of your theories?

If you don't like the methodolgy please feel free to make a suggestion. You see I am willing to put my money where my mouth is. This isn't BS this is real world real evidence. Do you agree with this?

You can also calculate pwoer mathematically by looking at area under a curve. But this only works with purely resistive loads. You really really need to look at AC power theory to have a basic understanding of power factor.


----------



## JeremyC

DUDE! Hey it is your damn name...

MUSIC... Not a clipped sine wave. 

With an amp UNDER the RMS rating of a speaker. 

Now I'm just being a tard. 

You guys have fun, I'm cooking some popcorn.



MarkZ said:


> The square wave has more energy, but this is due to the fact that they increased the amplitude of the (clipped) sine wave to achieve this square wave. By a lot.


Yep, that was one of the light bulbs that went off when I re-read everything.


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## qwertydude

Music would be difficult to produce consistent repeatable results.

The point of the argument is about heat build up in woofer coils due the type of signal being fed. This means that regardless of the type of signal it has to be clean power. Hence the overkill of a 250w RMS amplifier. That way I never drive the amp into clipping which is no doubt a proven woofer killer.

The point I'm proving is with the same amplitude, not cranking the volume up, if you're at the thermal limit of the woofer and then switch to a square wave you'll burn the woofer.


----------



## cmayo117

94VG30DE said:


> The reason we know you are an engineering student is the condescending tone and know-it-all attitude. By all means, continue to argue semantics based on physics without thermo, covering information that's already been addressed, all while blatantly ignoring real-world use case. To ensure you continue to be God's gift to the world, make certain that you carry this attitude into your first engineering position. You'll do great.


Alright. I'm not sure what was condescending about that. I pretty much admitted that I'm not that strong in Thermodynamics.


----------



## left channel

I think you are missing the point of this discussion. We are talking about blowing a speaker because you sent a clipped signal from an amp that is below the rating of the sub. The only way to properly test this is by actually clipping the same signal that you are sending to the sub. Shouldn't be hard to reproduce at all. Just crank the gain.



qwertydude said:


> Music would be difficult to produce consistent repeatable results.
> 
> The point of the argument is about heat build up in woofer coils due the type of signal being fed. This means that regardless of the type of signal it has to be clean power. Hence the overkill of a 250w RMS amplifier. That way I never drive the amp into clipping which is no doubt a proven woofer killer.
> 
> The point I'm proving is with the same amplitude, not cranking the volume up, if you're at the thermal limit of the woofer and then switch to a square wave you'll burn the woofer.


----------



## MarkZ

qwertydude said:


> I'll post a video. I have a spare bookshelf speaker lying around and will reproduce this experiment as stated. Continuous sine wave power in a woofer vs continuous square wave power in a woofer.
> 
> The experiment will be as follows. My computer will act as a signal generator I will produce sine wave and square waves. I will use my Boss AR1500M amp powered by a regulated 13.8 volt pwoer supply. I will use 20 hz as the example frequency unless the woofer is exceeding mechanical capabilities before reaching thermal capabilities. I won't exceed the power limits of the woofer so that in sine wave you can see it would run indefinitely. I will then without changing output settings of frequency or amplitude switch over to square wave and you'll see it will burn out.
> 
> If I post this video and prove square waves can burn out a subwoofer vs the equivalent sine wave. Will you post a retraction of your theories?
> 
> If you don't like the methodolgy please feel free to make a suggestion. You see I am willing to put my money where my mouth is. This isn't BS this is real world real evidence. Do you agree with this?
> 
> You can also calculate pwoer mathematically by looking at area under a curve. But this only works with purely resistive loads. You really really need to look at AC power theory to have a basic understanding of power factor.


Thanks for the lesson, numbnuts. But a guy who doesn't even know what the Fourier series of a square wave is really has no business trying to explain introductory electronics to anybody.

FWIW, I thought I made it quite clear that I was talking about the energy content of the waveforms (which is why I dealt separately with the waveforms and with the impedances). The energy content of the waveforms is independent of the load. In fact, it doesn't even need to be an electrical signal.

I know what you're saying about "back EMF" (it's usually referred to as motional EMF in audio, to distinguish it from back EMF which is another phenomenon), but it's a non-factor here. For two reasons. First, it's already incorporated into the impedance of the speaker. Second, every car audio amp I know of effectively damps this EMF, which is helped by the fact that every car audio amp I know of also has a ~0 ohm output impedance. [There might be some amps where this is not the case, like what the hippies use with their tube output stages or the "audiophiles" use because they hate global NFB (usually because they don't understand it), but in car audio that's not very typical.]

I think you'll understand things better if you think about them in the frequency domain. Then you'll realize that subwoofers don't have a harder time with high frequencies than with low frequencies. Because that's what we're talking about here. We're comparing two signals:

"Clean" = A*f0
"Dirty" = A0*f0 + A3*f3 + A5*f5 + ... , where A = A0 + A3 + A5 + ...

All clipping is doing is moving the energy from low frequency to high frequency. That's it. That sucks for tweeters on a passive network, but we're not talking about that.

Your argument started out with the DC story, which you quickly realized was silly, and now relies on motional EMF. Evidently, your stance now is that motional EMF blows speakers. Which, put another way, means that sealed boxes blow speakers. :laugh:

Anyway, you're free to try to blow whatever speakers you want. But I believe you lack the technical expertise to perform the test correctly.


----------



## Hanatsu

Omg, it's astounding to me that some people still argue about this dirty power crap...

Should listen to what Mark says ^^


----------



## JeremyC

MarkZ said:


> All clipping is doing is moving the energy from low frequency to high frequency.


I think I just had another light bulb go off. 

When I'm setting gains using my o-scope (yes mark I know your view on this ;-) ) 

The clipped line is never a strait line like it is while moving up and down. If I add in enough clipping and increase the time, you can actually see little up and down lines inside of the clipped part of the wave.

Would what I'm seeing actually be the freq changing from low to high?


----------



## cmayo117

JeremyC said:


> I think I just had another light bulb go off.
> 
> When I'm setting gains using my o-scope (yes mark I know your view on this ;-) )
> 
> The clipped line is never a strait line like it is while moving up and down. If I add in enough clipping and increase the time, you can actually see little up and down lines inside of the clipped part of the wave.
> 
> Would what I'm seeing actually be the freq changing from low to high?


Is this what it looks like: MATLAB - Square Wave from Sine Waves Demo


----------



## t3sn4f2

cmayo117 said:


> Is this what it looks like: MATLAB - Square Wave from Sine Waves Demo



Found this a while back.


----------



## MarkZ

JeremyC said:


> I think I just had another light bulb go off.
> 
> When I'm setting gains using my o-scope (yes mark I know your view on this ;-) )
> 
> The clipped line is never a strait line like it is while moving up and down. If I add in enough clipping and increase the time, you can actually see little up and down lines inside of the clipped part of the wave.
> 
> Would what I'm seeing actually be the freq changing from low to high?


Yes and no. Even if you had a perfectly flat top, it's formed from the addition of high frequencies. Basically, any time you see a sharp transition -- like the corner of the smooth sine wave to the flat top -- it's formed from high frequency energy. The wiggle you see at the top can be due to a number of different things. It could be oscillations in the power supply, or it could be high frequency rolloff (if you lowpass filter a square wave -- actually _remove_ some high frequencies -- you'll get some of that wiggle).


----------



## 94VG30DE

cmayo117 said:


> Alright. I'm not sure what was condescending about that. I pretty much admitted that I'm not that strong in Thermodynamics.


Sry, selected the wrong text. Meant to quote qwertydude...


----------



## qwertydude

I didn't realize DC is irrelevant, it's still very relevant when talking square waves.

I'm talking about the energy content of waves of the same amplitude. If you take a the integral of a square wave you'll find it delivers equivalent power to a simple DC signal ie 0 hz at maximum amplitude. You just get a little more cooling because the woofer is moving back and forth but but the tops and bottoms of those waves is still having effectively DC current going through the coils while motionless which heats them up, I don't care about the high frequency subharmonics, they transfer little power to begin with and it seems you're trying to use those to distract everyone.

You still get cooling from the sharp transition to the opposite amplitude but the cooling from that is far less due to the thermodynamic properties of fluid cooling.

Every time you were talking about a clipped signal you just simply stated flattening the top of waves, if you do that you change the amplitude of the wave. Hence you're always going to be applying less power and would get lower overall temps.

The point I was making is more inline with how people blow woofers, feeding a clipped signal of the same amplitude as a clean signal. Push an amp too hard and you won't get any more current out of it, but you will still be applying more damaging power. Flat high voltage signals are still more damaging than constantly moving signals of the same amplitude due to thermodynamics and increased power transfer and the motional audio.

And take a look at what you just said about damping you think damping just makes all that excess energy disappear? You said the effective impedance of the amplifier outputs is 0 ohms. So where exactly would the excess motional audio, complex power, whatever you want to call it dissipate? 0 ohms certainly won't heat up due to power transfer functions. So the only place it will dissipate is the place with highest impedance. Therefore excess movement due to both the field collapse and momentum of the speaker will be braked by the amp but dissipated entirely by the voice coil. This will obviously add even more heat on top of sitting motionless while having effectively DC current applied. The faster the change as in the sharper those corners the more braking force will be applied by a 0 ohm amplifier, so those hippie amps may not stop the motional audio but it won't instantly convert it to heat either.

I can understand the point you're making with the furrier analysis and yes it transfers power very similarly to how the equation tells you. The same power is transferred regardless of frequency. But the flip side is you still haven't given an explanation on how that heat is removed. That's what blows woofer in the end. Too much power in, not enough removed in the form of heat, that equals temperature rise, that means blown woofer.

You keep focusing on the input of power and not enough on how you're removing that heat. In fact you don't touch on it at all with any scientific accuracy.


----------



## junglejuice72

JeremyC said:


> That doesn't sound like a fried coil. If you saw that much smoke, and it came from the coil, continuing to use the sub would have caused more problems.
> 
> It sounds like there was something on the coil from the build process that shouldn't have been there.
> 
> You ran the sub, burnt off the material (saw the smoke), and thought you screwed up the coil.
> 
> But then you gave it more power and it kept working.


It is part of my job to know the smell of burning electrics, I strongly suspect it was the insulation on the coil that was cooking as I have smelt that same smell many times at work.....

JJ


----------



## Richv72

Probably just the excess flux left on the coil.


----------



## MarkZ

qwertydude said:


> I didn't realize DC is irrelevant, it's still very relevant when talking square waves.


The reason it's irrelevant has been explained to you several times and by multiple people (with links), and the math has been put in front of you. *A square wave does not have a DC component.* It doesn't have any frequencies lower than what the corresponding sine wave has.




> I'm talking about the energy content of waves of the same amplitude. If you take a the integral of a square wave you'll find it delivers equivalent power to a simple DC signal ie 0 hz at maximum amplitude. You just get a little more cooling because the woofer is moving back and forth but but the tops and bottoms of those waves is still having effectively DC current going through the coils while motionless which heats them up, I don't care about the high frequency subharmonics, they transfer little power to begin with and it seems you're trying to use those to distract everyone.


1) The coil is never motionless. The reason for this has been explained to you, and it has to do with the lowpass properties of the system. Lycan explained this pretty well in the posts I suggested to you.
2) You may not care about the harmonics, but those are precisely what turns a sine wave into a square wave. In fact, that's the _only_ linear combination of sinusoidal eigenfunctions that can. So when you say you don't care about them, it simply means that you can't wrap your head around it. Because those harmonics _completely and entirely_ describe the difference between a sine and square wave.




> Every time you were talking about a clipped signal you just simply stated flattening the top of waves, if you do that you change the amplitude of the wave. Hence you're always going to be applying less power and would get lower overall temps.


Exactly my point! Why would you want to compare a situation where the volume knob is higher in one case than in another? That doesn't make any sense. The question is: is clipping harmful to speakers? So, to answer that question, you need to use the _exact_ same input waveform, only set your saturation point differently (eg. compare a 50w amp to a 500w amp).

The question you seem to want to answer is: do idiots with no self-control over the volume knob blow speakers? I think we already know the answer to that, and it has nothing to do with the amplifier or the shape of the waveform.




> And take a look at what you just said about damping you think damping just makes all that excess energy disappear? You said the effective impedance of the amplifier outputs is 0 ohms. So where exactly would the excess motional audio, complex power, whatever you want to call it dissipate? 0 ohms certainly won't heat up due to power transfer functions. So the only place it will dissipate is the place with highest impedance. Therefore excess movement due to both the field collapse and momentum of the speaker will be braked by the amp but dissipated entirely by the voice coil. This will obviously add even more heat on top of sitting motionless while having effectively DC current applied. The faster the change as in the sharper those corners the more braking force will be applied by a 0 ohm amplifier, so those hippie amps may not stop the motional audio but it won't instantly convert it to heat either.
> 
> I can understand the point you're making with the furrier analysis and yes it transfers power very similarly to how the equation tells you. The same power is transferred regardless of frequency. But the flip side is you still haven't given an explanation on how that heat is removed. That's what blows woofer in the end. Too much power in, not enough removed in the form of heat, that equals temperature rise, that means blown woofer.
> 
> You keep focusing on the input of power and not enough on how you're removing that heat. In fact you don't touch on it at all with any scientific accuracy.


If you don't think I've addressed it, then you don't understand the point I'm making at all! The heat is removed in the same way that it's removed with a single sine wave, or any other combination of sine waves. The point is that a square wave is not special -- it's merely a particular combination of sine waves. The burden of proof is on you to demonstrate that the motion of the coil stops for longer than the time constant of heating (which Lycan already addressed earlier in the thread... have you read it yet?). Even if the subwoofer was perfectly capable of reproducing a perfect square wave (it's not... it's a LPF), and even if you were delivering a max amplitude 20Hz square wave to the subwoofer (not realistic for music), the coil would _still_ be moving 40 times per second. If something is moving 40 times per second, no rational person would say that it's standing still. 25ms is a hell of a lot shorter than the time constant of heating, which (as Lycan described) is very slow.


----------



## cmayo117

junglejuice72 said:


> It is part of my job to know the smell of burning electrics, I strongly suspect it was the insulation on the coil that was cooking as I have smelt that same smell many times at work.....
> 
> JJ


Voice coils aren't insulated.


----------



## minbari

cmayo117 said:


> Voice coils aren't insulated.


how do you mean? the wire from voice coils is certainly insulated. otherwise you wouldnt have a coil.


----------



## cmayo117

minbari said:


> how do you mean? the wire from voice coils is certainly insulated. otherwise you wouldnt have a coil.


Ok yea that's true. But the insulation is just like a thin coating. It doesn't usually smoke that much when it melts.


----------



## minbari

cmayo117 said:


> Ok yea that's true. But the insulation is just like a thin coating. It doesn't usually smoke that much when it melts.


I would disagree. depends on how much you heat it. it is a lacquer material. it will smoke lots if you start burning it off. by then the sub is basically dead.


----------



## chad

junglejuice72 said:


> It is part of my job to know the smell of burning electrics,
> JJ


Dunno that I would advertise/be proud of that. It's my job to prevent that smell.



cmayo117 said:


> Ok yea that's true. But the insulation is just like a thin coating. It doesn't usually smoke that much when it melts.


It smokes like a motherfucker if you do it right


----------



## qwertydude

What I'm still trying to point out is you're taking subwoofer movement over a total of time. 40 times per second of cycles. I'm talking about the absolute movement of the woofer at any given time. The derivative of the waveform.

The subwoofer and amp may act as a low pass filter and round off the corners of the square wave but it still sits at the tops and bottoms in effect motionless. It may have harmonics, it may bounce a very little bit up and down, but the dominant signal that's still transferring the most power is still the high constant voltage. And high damping amps only serve to further ensure it sits as still as possible with the least harmonics. The high damping would also add to the heat generation.

I understand there may be some harmonics that might make a slight bit of movement but for all intents and purposes the woofer does sit motionless. For more time than it spends in motion, or if you want since "motionless" seems to set you off onto tangents, sits at much lower absolute velocities than in a sine waves for any given time within the tops and bottoms of the square wave. Whereas a sine wave it is always in absolute motion, it never stops theoretically or otherwise. And while it sits relatively motionless it has current flowing through it heating coils up. And the rapid pop to the reverse doesn't cool as well as the smoother more constant motion of a sine wave movement.

But simply reducing power to the subwoofer by clipping the wave down to nothing proves nothing. And in my experiments I never touched the volume controls or the amplitude control on the signal generator. The only thing I did was switch waveform shape, same amplitude.

So it could be said still if you're on the edge of a woofers thermal capabilities but well within the amps limits a bad signal can bring it over the top. Not an idiot turning up the volume.


----------



## minbari

qwertydude said:


> What I'm still trying to point out is you're taking subwoofer movement over a total of time. 40 times per second of cycles. I'm talking about the absolute movement of the woofer at any given time. The derivative of the waveform.
> 
> The subwoofer and amp may act as a low pass filter and round off the corners of the square wave but it still sits at the tops and bottoms in effect motionless. And high damping amps only serve to further ensure it sits as still as possible with the least harmonics. The high damping would also add to the heat generation.
> 
> * I understand there may be some harmonics that might make a slight bit of movement but for all intents and purposes the woofer does sit motionless for more time than it spends in motion, whereas a sine wave it is always in absolute motion, it never stops theoretically or otherwise. And while it sits relatively motionless it has current flowing through it heating coils up. And the rapid pop to the reverse doesn't cool as well as the smoother more constant motion of a sine wave movement.*
> 
> But simply reducing power to the subwoofer by clipping the wave down to nothing proves nothing. And in my experiments I never touched the volume controls or the amplitude control on the signal generator. The only thing I did was switch waveform shape, same amplitude.
> 
> So it could be said still if you're on the edge of a woofers thermal capabilities but well within the amps limits a bad signal can bring it over the top. Not an idiot turning up the volume.



I havent read the whole argument, but what you are saying is absolutely true. simple power under the curve. squarewave has more of it


----------



## chad

But regardless, at say, 40 cycles the CONE IS NOT STANDING STILL at the peaks, it's not happening EVER, that coil cannot control that amount of inertia over that short of time frame. Then to compound this one can say that the heating "while it is standing still" is due to "lack of cooling" Well, that air is still moving in there, violently in that VERY VERY short time that the cone is "Standing still" that is not in reality....

500W RMS of squarewave=500W RMS of sinewave.. period.

One thing tears up speakers (other than idiots with screwdrivers and toddlers) TOO MUCH POWER, be it mechanical or thermal, the ONLY thing is TOO MUCH POWER.

If this were not the case then synth pop and the advent of digital audio recording in the 80's would have been flat out devastating to speaker drivers.


----------



## chad

minbari said:


> I havent read the whole argument, but what you are saying is absolutely true. simple power under the curve. squarewave has more of it


Correct, when measuring P-P voltage.


----------



## cmayo117

chad said:


> It smokes like a motherfucker if you do it right


Haha ok so maybe I was wrong. The one time I burnt up a coil it didn't smoke at all, but that was a much smaller speaker. And I guess it partially depends on the type of insulating coating that's used.


----------



## chad

Depends on how you do it. If it's from over excursion then it likely will not smoke, or from a hit so sudden in voltage that it simply opens the coil. But a nice slow cook will smell like hell.


----------



## cmayo117

So, what really matters is the average power dissipated over time. Once an amplifier starts clipping, the amplitude will not increase any more, but the average power can continue to increase. Right? So clipping itself won't harm the coil as long as the average power dissipated isn't more than the coil can handle, which is true no matter what the waveform.


----------



## MarkZ

qwertydude said:


> What I'm still trying to point out is you're taking subwoofer movement over a total of time. 40 times per second of cycles. I'm talking about the absolute movement of the woofer at any given time. The derivative of the waveform.
> 
> The subwoofer and amp may act as a low pass filter and round off the corners of the square wave but it still sits at the tops and bottoms in effect motionless. It may have harmonics, it may bounce a very little bit up and down, but the dominant signal that's still transferring the most power is still the high constant voltage. And high damping amps only serve to further ensure it sits as still as possible with the least harmonics. The high damping would also add to the heat generation.


Damping isn't going to reverse the effect of lowpass filtering (thankfully...). Anyway, you're underestimating how poorly a subwoofer will reproduce a square wave. Look at t3sn4f2's post again. But this doesn't even matter. 25 ms (which is the absolute worst case scenario, BTW) _is not long enough for the subwoofer to heat up._




> And the rapid pop to the reverse doesn't cool as well as the smoother more constant motion of a sine wave movement.


Is that so? Explain.




> But simply reducing power to the subwoofer by clipping the wave down to nothing proves nothing. And in my experiments I never touched the volume controls or the amplitude control on the signal generator. The only thing I did was switch waveform shape, same amplitude.


Then you did it wrong. A square wave with amplitude A is _not_ the same as a clipped sine wave with amplitude A. This should be evident if you compare figures 1 and 2 on Perry Babin's website (linked to earlier).


----------



## jhsellers

MarkZ said:


> All of this is irrelevant, because
> 1) the subwoofer never stops moving -- *"flat tops"* are lowpass filtered electrically and mechanically
> 2) even if the sub could faithfully reproduce *"flat tops"*....





qwertydude said:


> That's also one reason why square wave don't play well in 120v power systems like those 12v to 120v inverters. It's because a modified sine wave doesn't play well with motors (inductive load) efficiency is reduced 20% due to reactive power increasing the heat in the motor for the same amount of work done. A square wave can reduce this efficiency down to 50% further increasing heat a tremendous amount. Imagine 50% more heat for the same amount of work. That's what a lot of lay people don't understand about power factor. And power factor has a lot to do with clipped signals, and square waves.





MarkZ said:


> THAT'S what the discussion is about -- whether clipping hurts speakers, not whether idiots and their volume knobs hurt speakers.


_*Here come old flat top
He come groovin' up slowly
He got joo joo eyeballs
He one holy rollers*_

I think we should use FLAT TOP to describe a volume junkie from now on. 

Querty has lost this argument - 

A) There is no DC component in audio signals - not even test frequency tones - unless there was "DC offset" included, but an audio amp won't normally reproduce DC offset to a speaker output. 

B) Power is power - integral under the curve. To produce a "square wave" of identical power as a non-clipped "sine wave", it would have to start with a much higher magnitude sine function (of the same fundamental frequency), clipped to the same "peak voltage" (to which quertydude keeps referring), plus it would have an unusually high component of higher frequency harmonics, which give the "square wave" it's traditional fast leading edge. (this is why, Q-D, that Mark keeps telling you that you're not comparing apples to apples...) 

If you were to test two identical drivers, with two signals - one "clipped", one sinusoidal, but both with IDENTICAL power levels (RMS) - both drivers would play, and last, about the same. Speakers can play square waves, they just sound different. 

I'm not EVEN sure why you branched into the motor load tangent of discussion. Audio drivers are nowhere near the classification of inductive loads like machines. And additional motor heating isn't so much a by product of the "square waves" as it is from slower operating speeds on PWM drives. Inverter drives have their own problems, but this doesn't relate to the argument here in this thread. 

Flat top = volume knob abuse? 

Back to lurking,
John


----------



## minbari

jhsellers said:


> _*Here come old flat top
> He come groovin' up slowly
> He got joo joo eyeballs
> He one holy rollers*_
> 
> I think we should use FLAT TOP to describe a volume junkie from now on.
> 
> Querty has lost this argument -
> 
> *A) There is no DC component in audio signals - not even test frequency tones - unless there was "DC offset" included, but an audio amp won't reproduce this to a speaker output. *
> 
> B) Power is power - integral under the curve. To produce a "square wave" of identical power as a non-clipped "sine wave", it would have to start with a much higher magnitude sine function (of the same fundamental frequency), clipped to the same "peak voltage" (to which quertydude keeps referring), plus it would have an unusually high component of higher frequency harmonics, which give the "square wave" it's traditional fast leading edge. (this is why, Q-D, that Mark keeps telling you that you're not comparing apples to apples...)
> 
> I'm not EVEN sure why you branched into the motor load tangent of discussion. Audio drivers are nowhere near the classification of inductive loads like machines. And additional motor heating isn't so much a by product of the "square waves" as it is from slower operating speeds on PWM drives. Inverter drives have their own problems, but this doesn't relate to the argument here in this thread.
> 
> Flat top = volume knob abuse?
> 
> Back to lurking,
> John



I agree with everything but this. a full squarewave is still alternating, but the portions of the wave where it sits on a rail _IS_ DC. it doesnt have to be offset.

I wont argue the effect on the woofer, no way its gonna make the woofer go-stop-go-stop. (unless it is 2hz, that is actually kind of fun to watch)


----------



## JeremyC

I feel so much smarter after reading all of this.


----------



## chad

minbari said:


> I agree with everything but this. a full squarewave is still alternating, but the portions of the wave where it sits on a rail _IS_ DC. it doesnt have to be offset.
> 
> I wont argue the effect on the woofer, no way its gonna make the woofer go-stop-go-stop. (unless it is 2hz, that is actually kind of fun to watch)


AC or DC has *nothing* to do with the shape of the waveform. If you took a sine wave and cut off everything above or below the X axis it's DC.

Sitting on the rail or not a sine wave can LITERALLY sit on the rail too.


----------



## chad

cmayo117 said:


> So, what really matters is the average power dissipated over time. Once an amplifier starts clipping, the amplitude will not increase any more, but the average power can continue to increase. Right? So clipping itself won't harm the coil as long as the average power dissipated isn't more than the coil can handle, which is true no matter what the waveform.


****en-A


----------



## MarkZ

minbari said:


> I agree with everything but this. a full squarewave is still alternating, but the portions of the wave where it sits on a rail _IS_ DC. it doesnt have to be offset.


Jesus H. Christ...

Edit: This is getting ****ing ridiculous. I'm done responding to any more posts. Except to provide links to previous posts in the thread. *Everything* has already been covered!

Post 82.



MarkZ said:


> sqshoestring, when you see those flat tops, those are not quick flashes of DC. A square wave (note the word "wave") is wholly AC -- no DC component whatsoever. Want to turn a sine wave into a square wave? Add *high frequency* harmonics. High frequencies are not DC.
> 
> Why is this important? For four reasons.
> 
> 1) the addition of high frequency harmonics, which is what happens when you add sharp discontinuities (like by flattening the top of the wave), can find their way into tweeters ... making clipping dangerous for tweeters on the other side of a passive crossover. Not because of any weird DC argument. But rather, because the power content becomes more concentrated at high frequencies. Note that this has nothing to do with subwoofers though.
> 
> 2) To suggest that DC is at play here is stupid. When something moves 30, 40, 50 (or more) times per second, it sure as **** ain't standing still! If you had a hot bowl of soup and you moved it back and forth 30 times per second, it would cool off pretty damned quickly!
> 
> 3) this is related to #2, air movement acts as a lowpass filter. Turn a fan on and off 30 times per second (ignoring electrical lowpass filtering) and it's gonna feel the same as if it was on steadily (minus duty cycle issues). So, if forced air convection is the issue here, and it seems to be, then the lowpass filter action of the air movement itself will smooth these "flat tops".
> 
> 4) Regarding subwoofers, they will generally not follow the square wave faithfully. Subwoofers act as lowpass filters too. Both mechanically and electrically (this is where inductance comes in). This will have the effect of rounding off those corners. It's safe to say that a subwoofer being fed a 30Hz square wave will NEVER stand still.
> 
> Edit: And as lycan describes above, the thermal dissipation itself acts as a lowpass filter. Temperature doesn't change as quickly as the signal itself. The temperature will not change at 30 cycles per second. It acts much slower. It takes time to cool things down and heat them up. Even if the coil were to stand still for ~20ms (25Hz square wave half-period), and then move and stand still, etc, the coil temperature would be unaffected by such brief stand-still times


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## donnieL72

AC/DC doesn't matter as long as the current flowing thru the voice coil doesn't drive the heat up enough to exceed the thermal limits of the coil. A clipped signal may make it sound like crap, but as long as the current is in check, then all's well. When the speaker gets to the top or bottom of a clipped signal, we're talking milliseconds, it does not have time to sit there and cook. It's not like it's seeing a pure square wave at 2 Hz. Music is dynamic with only the peaks that might be clipped. There will still be adequate airflow to keep it cool.

Excessive power that exceeds the thermal handling of the voice coil blows speakers. 

Flame away.


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## trumpet

This has been one of the most entertaining threads recently, but I think it's run its course. As Mark pointed out, this is just going in circles now, again and again.


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## minbari

chad said:


> AC or DC has *nothing* to do with the shape of the waveform. If you took a sine wave and cut off everything above or below the X axis it's DC.
> 
> Sitting on the rail or not a sine wave can LITERALLY sit on the rail too.


if it is not alternating, then its DC. 90% of the time a squarewave is NOT alternating. 


I didnt say anything about frequency, I fully understand that at 40hz, 120hz or higher, it is moving pretty fast and will behave mostly like a sinewave because of it with a speaker attached. but you cant tell me that a squarewave doesnt sit at a DC level most of the time.


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## MarkZ

minbari said:


> if it is not alternating, then its DC. 90% of the time a squarewave is NOT alternating.
> 
> 
> I didnt say anything about frequency, I fully understand that at 40hz, 120hz or higher, it is moving pretty fast and will behave mostly like a sinewave because of it with a speaker attached. but you cant tell me that a squarewave doesnt sit at a DC level most of the time.


Alternating DC FTW! :laugh:

Post #140. (Please read the Wikipedia link. Then you'll understand.)



MarkZ said:


> square wave = sum(A/N*fN) = A0*f1 + A0/3*f3 + A0/5*f5 + ...
> 
> In other words, a square wave is composed of odd-order harmonics that are integer multiples of the fundamental. You can read more about it on wikipedia, paying careful attention to the first equation (which is the one above).


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## left channel

minbari said:


> if it is not alternating, then its DC. 90% of the time a squarewave is NOT alternating.


That ridiculous! 10% of the time it IS alternating. Alternating is alternating no matter how you look at it.


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## minbari

left channel said:


> That ridiculous! 10% of the time it IS alternating. Alternating is alternating no matter how you look at it.


ok, what if it only alternated once a week? it went up to 30vdc, stayed there for a week then alternated to -30vdc? is it DC while it is at that level for the week between the alternating state?

this is no different, if it take .1mS to go from -30Vdc to +30vdc, and it does this every 25mS, then the alternating state has very little effect. it is sitting at a DC level most of the time.

again, we dont listen to square waves, so the whole argument is mathimatical dick swinging.


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## Richv72

If your clipped signal is so bad its turning into a square wave, you need a new amp.


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## MarkZ

minbari said:


> ok, what if it only alternated once a week? it went up to 30vdc, stayed there for a week then alternated to -30vdc? is it DC while it is at that level for the week between the alternating state?


If it alternates once a week, then its frequency is 1/1wk ~ 0.0000001 Hz.

.0000001Hz is close enough to zero to be considered DC in any practical sense. 20Hz is not.

Obviously this "mathematical dick swinging" is important, because it's led several people to mistakenly believe that clipping blows speakers because DC is bad for speakers.

All of these topics have already been dealt with. You guys are the most stubborn bunch of motherfuckers I've ever encountered, because you _refuse_ to read the thread, and instead choose to rehash the same arguments over and over again. 

Post #81:



lycan said:


> Strictly speaking, there are no DC signals.
> 
> Practically speaking, "how long" must a signal remain "stationary" before the system ... _any_ system ... recognizes it as DC?
> 
> The answer is this : the signal must remain stationary for a time interval equal to (or greater than) several of the system's slowest, or longest, time constants
> 
> Case in point : if the signal to a driver changes FASTER than the THERMAL time constants of the sub (coil, former, etc.), the signal is NOT equivalent to DC.
> 
> Thermal time constants of subs are longer (i suspect) than 25 msec (half of a 20Hz cycle). Therefore, any signal of interest to a sub ... sinewave, clipped sinewave, or squarewave ... will NOT be recognized as DC by the sub.
> 
> Bottom line : only two things kill subs : power, or physical abuse. The _shape_ of the signal has nothing to do with it ... only the _power_ of the waveform.


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## chad

minbari said:


> but you cant tell me that a squarewave doesnt sit at a DC level most of the time.


Motherfucking right I can. Because if it's alternating current it's alternating current, if it's direct current, it's direct current and doesn't not cross the X axis. No matter if it's a squarewave or a funny clown balloon wave.


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## squeak9798

minbari said:


> ok, what if it only alternated once a week? it went up to 30vdc, stayed there for a week then alternated to -30vdc? is it DC while it is at that level for the week between the alternating state?
> 
> this is no different, if it take .1mS to go from -30Vdc to +30vdc, and it does this every 25mS, then the alternating state has very little effect. it is sitting at a DC level most of the time.
> 
> again, we dont listen to square waves, so the whole argument is mathimatical dick swinging.


It is important because, as Mark said, it confuses people as to the issue of what actually causes damage to the driver.

I don't think anyone can explain why you are wrong any differently than has already been explained multiple times in this thread. At this point either reread the thread to learn why you are wrong, reread the posts Mark has quoted to learn why you are wrong, or just accept you are wrong at face value. Regardless, you _are_ wrong and there is no post you make that will change that fact.


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