Axiom Home Page Forums General Discussion Technical Questions Clipping

Exactly. If you run at normal levels with (say) a 50W amp only a small amount of the power is in the frequency range which gets through the crossover into the tweeter.

If you take that same 50W amp and drive it into hard clipping, the flat top and sharp edges of the resulting signal drive relatively more of the power into the high frequency ranges (that "kazoo" sound) and so you can easily get MORE power into the tweeter with a clipping 50W amp than you can with a non-clipping 100W or 200W amp.

The big issue is that if you have a 500W amp and turn it up to the point where tweeter damage could occur it's going to be REALLY FREAKIN' LOUD but if you have a 50W amp and drive it into clipping you can fry your tweeters but the overall sound is not going to be that loud.

That's the problem with a small amp. You turn it up... it's not loud enough... you turn it up more... it doesn't seem to be getting any louder... you turn it back down a bit... and the next day you notice that one of your tweeters isn't working.

If you take that same 50W amp and drive it into hard clipping, the flat top and sharp edges of the resulting signal drive relatively more of the power into the high frequency ranges

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It's only partially correct and often over-exagerated because it's frequently quoted.

First the flat top does not contain high frequencies. Flat is associated with low frequencies.

Sharp edges indeed, contain high frequencies but their contribution is very small. If you do actual Fourier transform you'd be amazed how small the power increase in the high f domain is due to distortion. It's not even that you make a pure square wave out of a sinusoidal signals. You just clip the very top of the sin.

The danger is that by driving an amp to clipping the overall power increases and exceeds the amp rms rated power. That, in turn increases the power in high f which delivered to tweeters. The wave distortion by itself has only a small contribution.

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...because there's no more juice...
(...)
So, if there is no more juice than why is there a concern of blowing the speaker?

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I think you're confusing power side and signal side here. When he says "no more juice" he means on the power side of the amp circuit, not the signal side. When the power side sags, you end up with a distorted signal.

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If you have a 300 W or 400 W rated speaker what harm can be done from a 50W amplifier? A 50W amplifier can not put out more than 50W, period. The speaker woun't even break a sweat.

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Except all 50W pushes aren't created equal. As clipping increases, the wave starts to resemble a pulse (or square) wave... the best naturally occuring type of wave to freeze voice coils. You can probably push a 400W rated speaker many times past it's rating with a 200Hz sine wave, feed the same speaker a fast pulse and it'll do a Vesuvius impression rather quickly.

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A real danger comes from 'matching' amplifier and speaker. For instance, if you have a 200W rated speaker and 200W amplifier than you have to watch for clipping.

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You do have a point here, indirectly. A higher (amp rating:speaker rating) ratio will either increase the damage done in a period of time, or drop the period of time required to do the damage.

Bren R.

Thanks for the info to you all. That link you sent, BrenR, is most like what I hear only louder. A cd I bought by Doyle Bramhall II sounded like that because it must have been recorded too loudly. But the sound I get is probably due to the cheap components I own. I have a Technics receiver and Infinity RS525 speakers. They are getting a bit old anyway. Of course, the speakers sound fine till I try to play them too loud. Again thanks to everyone.

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The danger is that by driving an amp to clipping the overall power increases and exceeds the amp rms rated power. That, in turn increases the power in high f which delivered to tweeters. The wave distortion by itself has only a small contribution.

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Again, everyone's picking on you, and I don't want to add to that, but it looks like you bring up good points, then aim them at the wrong targets.

Yes, clipping drives up RMS power... by definition, the root-mean-square of a compressed (or companded) signal will be higher.

Low frequencies CAN become saturated more quickly than high frequencies. Take this Rane page for instance. It seems to be an absolute smoking gun for your side of the argument. And the author HAS made sure to use examples that will support his theory perfectly.

I have taken issue in the past on a lot of Rane's corporate theories.. especially their clinging to damping factor as the be-all end-all in wire choice.

I gotta split, though... can't finish my train of thought until later.

Bren R.

That Rane's link that you gave proves my point exactly. I might have a problem to express it well in English (not my native language) but, once again:

The waveform distortion from clipping does not kill tweeters. It's just another internet myth perpetuated all over again. There is just not enough power from the extra high f harmonics.

Thanks for the link
Gena

I think I'll trust what the founders of Axiom tell me with 30 years at the NRC.

Gena, the following discussion which I've linked previously is possibly the most complete examination of possible clipping damage which is available online. Both the compression and harmonics theories are examined along with brief mention of other possibilities. As you'll note, it reaches no definite conclusion. This is part of the material which Dr. Lesurf originally prepared for introductory use by his students in electronics and physics at St. Andrews.

I had to drop this one mid-stream.

I was suggesting that it's not the whole story on either side.

Fourier says there's not enough POWER to blow a tweeter. And there isn't. There are MANY other forces at work. One is also, as you mentioned, that this forces the tweeters to take on more of their share of power - though that Rane article is suspect since it intentionally uses a low amplitude hi-freq with a burst of high amplitude lo-freq modulation for the author to prove his point... if you were to reverse the amplitudes, I could prove that low frequency drivers (ie: woofers) would blow first.

Damn, we're back to square one and haven't proven anything... except even "professional" companies (and Rane's one of the respected ones) may be trying to oversimplify.

So if I were to rebuild his Figures with the amplitudes reversed, I could prove that woofers would blow before tweeters... though that hardly ever happens. So what else do we look at?

Heat. So when you really overdrive a tweeter (even a ferrofluid cooled one like Axiom uses, which DOES help) as the wattage sent to the tweeter rises, so does the amount of heat generated, ever taken apart a tweeter? They're not nearly as easy to cool as a woofer with it's large basket.

So now that everyone's dug in their heels and given their side, the answer seems to be "nobody knows"... I like to hear others' opinions, many heads are better than one, but when trying to shed light on another's partial answer, suggesting another partial answer is the whole canonical truth is probably counter-productive.

Even Ian's quote is somewhat vague on what exactly it IS about clipping that melts down tweeters. But in the end, clipping kills drivers, what part of clipping it IS that kills them is still open for discussion it would seem.

I do agree with you that it's tough for the harmonics to generate enough extra power to fry a tweeter, but as others have said, it's easier for a lower powered amp to clip at a reasonable listening level (you originally said a 200W amp & 200W rated speaker would be a worse combination than a 50W amp and a 200W rated speaker; I contend it would be much harder and louder to push a 200W amp to clip than a 25W one, making the danger a low powered amp)

Bren R.

Excellent link, John.

Again, the modeling shows that even with the amplifier of the 'matched' power (speaker 100W, amplifier 100W) the damage from the distorted waveforms is, well, questionable. However, there's a firm belief that even a very low power amplifier can damage a high power speaker if clipped - see the quote from Ian. I think it's way off. Well, I can understand him - they are about to start selling new, 'powerful' amplifiers