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Clipping or Too Much Power?

kfalls said:
"Originally Posted by kahlfin1k View Post
If a distorted signal fried speakers every guitar amp ever would have blown speakers."

Clipping is distortion, but not all distortion is clipping. When the output waveform is different than the input waveform it's distorted. Example: Input waveform is a sine wave, output waveform is a sawtooth wave. An amplifier should only amplify the input not change it. A clipped output waveform has chopped tops and bottoms, so is different than the input, so is distortion.
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A guitar input is not distorted. Some guitar amps apply a pre drive circuit that will clip before the power amp or a digital circuit that emulates this sound. In this case the signal reaching the power amp WAS distorted already. However, that design concept came from the desirable sound of power amps clipping. That's why guitar players like tubes. They sound good when they clip. Analog SS does too though. Many guitar amps have no "overdrive" or distortion control or circuit. You basically turn up the gain until it clips and there's your fuzz. Guitar amp speakers are rated for way more power than the amp supplies so that they CAN be driven to clipping without blowing the speaker.
 
put me on the fence about ready to tip over to the clipping side. me thinks clipping will, if continuous over quite some time, in fact slow cook the VC into submission. how long this takes i can not tell you but i should think from as little as a few min.. i would guess the combination of speaker and amp to cause this is rare.
even more rare would be the person who would let this condition continue long enough to cause damage.
 
If I hadn't sold the tweeters out of them to a member here, I'd use my Pioneer CS-44's as sacrificial lambs, since I think they suck, and would connect them to my 7wpc Lepai amp and clip the hell out of with some song on repeat and then go to work (so I didn't have to listen to it all day) and see if they were still playing when I got home. I suspect they would be.
 
Oh boy, the myths. Going to make this short and sweet.

Clipping - by itself - does not kill speakers.

You never see woofers being blown up by an amp that doesn't exceed its RMS wattage rating. It's always the tweeters. Why? When an amp is cranked up into clipping, it's the bass that gets hit first - after all, that's what sucks the most power. Low to moderate levels of clipping are usually not discernible, especially at ear-ringing SPL. Peak power remains the same, but average power increases - and the tweeters get smoked first as they're usually the lowest rated in a multi-speaker (2/3-way) system.

Why did JBL write a paper on clipping? Well, I don't know, maybe they're, you know... selling things?
 
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Although there have been five pages of responses to this question (I have not read all of them) here is my take on the subject.

If you look at a pure tone sine wave it starts out vertical at zero crossing and then curves as it approaches the peak. The higher the amplitude, the more vertical the wave form will be at crossing zero. When the waveform peak becomes higher than the amp rail voltage, the sine wave clips like being cut horizontally with a knife. this means there will be a sharp (almost right angle) change in the waveform. If you do a Fourier transform of this wave form to convert from the time domain to the frequency domain, you see you have suddenly generated a long series of harmonics related to the fundamental (1KHz changes to 1KHz+2KHz+4KHz+8Khz.....etc.). Wave forms such as triangular with sharp corners also create substantial harmonics. These harmonics will decline in value over frequency but the first four or five can still be substantial. The total power output of the fundamental plus the harmonics can be quite a bit higher than the fundamental alone and also put a strain on the amplifier power supply.. Tweeters do not have the high power handling to withstand continuous clipping. Woofers can handle these momentary anomalies much better. Besides, harmonics generated from a clipped low frequency fundamental appear in the mid and high frequency range.
 
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Nope. Facts:

1- Clipping harmonics generate very little power. Do the FT, or read the Rane paper I have cited here many times. Blowing tweeters from clipped harmonics is a MYTH.

2- Speaker cone movement does NOT follow terminal voltage. That simply is not how speakers work. You can put a "flat" voltage into a cone and the cone will keep moving.

3- What appears to be "flat" segments of a waveform on a scope is NOT DC. In fact, creating flat segments requires a very harmonically rich signal.

4- Voice coils do NOT cool via motion. Ask any competent driver designer. Cooling is substantially radiative, not convective.

5- BIG amps will always present the greater clipping danger than small amps. Period. I don't care what stories you have heard. They are stories like the grandma who lived to 100 smoking a pack a day: either myths or random statistical outliers.

6- The JBL paper was written by the marketing dept., and was not approved by the engineering dept. Ditto for the AR paper released at the same time, which I helped write, but which was later rescinded.

Sorry to be cranky about this, but well-meaning people keep posting OLD information that has been long since discredited.


-k
 
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What happened here?

Omni Sound, Dallas, last century. A guy brought in his Thiel 04 speakers and PS Audio integrated (40 wpc?). Both 6" woofers were frozen and had that burnt smell. The amp was fine (can't remember if fuses were blown). I thought he had driven the amp so hard that it was in a constant state of clipping and this caused something in the voice coils to melt.

I don't see this as a blown speaker. I think of a blown speaker as one that has been ripped apart by too much clean power. I bet they scream TOO MUCH just before dying.
 
nailer said:
What happened here?

Omni Sound, Dallas, last century. A guy brought in his Thiel 04 speakers and PS Audio integrated (40 wpc?). Both 6" woofers were frozen and had that burnt smell. The amp was fine (can't remember if fuses were blown). I thought he had driven the amp so hard that it was in a constant state of clipping and this caused something in the voice coils to melt.

I don't see this as a blown speaker. I think of a blown speaker as one that has been ripped apart by too much clean power. I bet they scream TOO MUCH just before dying.
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Too much power to the woofers, plain and simple. If the volume knob wasn't touched, and a larger amp was used, the same thing would have happened. The only effect clipping had was to REDUCE the heating of the woofers very slightly, by directing about 1% of the amp's power to the tweeter, in the form of harmonics.

It can hurt one's brain, for sure: in this case, the 40 Watt amp might be putting out 100 Watts of square waves. BUT... that is not caused by the clipping, it is simply a matter of the volume setting. Using a big amp that didn't produce square waves would also put out 100W under those conditions and also blow the speakers.

Sheesh, after many, many hours of posting here, I should avoid this topic. I have already explained it generally, mathematically, drawn diagrams, given technical references and experimental setup for people to try. But, a new year, and a new crop of folks need to reconsider the "facts" they learned about small amps and speaker damage.

Smaller amps = safer speakers. Loud music = blown speakers.

-k
 
davidro said:
My understanding from the posts of Ken Kantor and other proponents is that it's too much power that blows speakers, not clipping. I still see a lot of usually knowledgeable members insist on the latter.

Which is correct? Let's settle the issue once and for all.
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Too much power will burn out woofers , clipping destroy tweeters ...
 
In the wrong hands, will a large amplifier be more capable of destroying an
efficient or high sensitivity speaker rather than a speaker considered a power hog?
 
tubed said:
In the wrong hands, will a large amplifier be more capable of destroying an
efficient or high sensitivity speaker rather than a speaker considered a power hog?
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Assuming that 'efficiency' translates directly to 'excursion' in this context (which is not always true), yes, mechanical destruction can result - popping the gap, tearing surrounds, etc.
 
tubed said:
In the wrong hands, will a large amplifier be more capable of destroying an
efficient or high sensitivity speaker rather than a speaker considered a power hog?
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Probably. I mean high sensitivity generally results from low xmax, small voice coil speakers in big, low damped enclosures. Pretty much a recipe for disaster for over powering, whereas low sensitivity speakers typically have smaller sealed enclosures (that better control the woofers excursion at high output levels), high xmax, and higher weighted cones, which takes more power to move the driver, and larger voice coils which can take a lot more power.

Nothing is absolute, but low sensitivity and high sensitivity speakers have certain common traits with other like designs.
 
89grand said:
Probably. I mean high sensitivity generally results from low xmax, small voice coil speakers in big, low damped enclosures. Pretty much a recipe for disaster for over powering, whereas low sensitivity speakers typically have smaller sealed enclosures (that better control the woofers excursion at high output levels), high xmax, and higher weighted cones, which takes more power to move the driver, and larger voice coils which can take a lot more power.

Nothing is absolute, but low sensitivity and high sensitivity speakers have certain common traits with other like designs.
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High sensitivity dictates a small voice coil? Naaaah. ;)

But yeah, I do wonder where the whole clipping myth came from. Was it just JBL's marketing paper? I never bought into it - anyone with a tenth-grade physics education should know better.
 
FWIW here is an excerpt from my Focal speaker owners manual:

About amplifiers
Contrary to what one might think, it
is not a too powerful amplifier that
might damage a loudspeaker, but
rather a lack of power. Actually if the
output level of the amplifier is too high
it will saturate and distort which will
irremediably damage the tweeter.​
 
JRSBat said:
FWIW here is an excerpt from my Focal speaker owners manual:

About amplifiers
Contrary to what one might think, it
is not a too powerful amplifier that
might damage a loudspeaker, but
rather a lack of power. Actually if the
output level of the amplifier is too high
it will saturate and distort which will
irremediably damage the tweeter.​
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So, in the same paragraph, Focal says that a "lack of power" will damage speakers. Then they immediately contradict themselves by saying "if the output level of the amplifier is too high".


Actually if the
output level of the amplifier is too high
it will saturate and distort which will
irremediably damage the tweeter
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This sure reads like an implication of too much power caused by harmonics doing the damage. Just my observation......................... not suggesting they're right or wrong.
 
bowtie427ss said:
So, in the same paragraph, Focal says that a "lack of power" will damage speakers. Then they immediately contradict themselves by saying "if the output level of the amplifier is too high".


This sure reads like an implication of too much power caused by harmonics doing the damage. Just my observation......................... not suggesting they're right or wrong.
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At first I thought it was contradictory too. After reading it a few times I think something was lost in translation from French to English. I think the second part of the paragraph Focal meant to say:

"If you have to turn your volume knob up to an extremely high level to reach the loudness you desire it will saturate...."

Meaning if your amp does not have enough power and you have to really crank the volume knob (go into clipping) you will damage the tweeters.
 
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