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I have a Yamaha 1103 that is rayed at 100 watts per channel and paradigm bookshelves that are rated at a maximum power input of 60 watts. This isn't a problem right?
 

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The Village Idiot
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As long as you don't play it at '11' all the time - no. Speakers are more susceptible to damage when you use an under powered amp - especially when you 'clip' the amp. The worse the clipping the more the signal the speaker sees a DC current which heats up the voice coil (motor).
 
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That amplifier is 80W per channel. But no you won't have a problem.
Minimum RMS Output Power per Channel
MAIN L/R
8 ohms, 20 Hz to 20 kHz, 0.04% THD
......................................................80W+80W
CENTER
8 ohms, 20 Hz to 20 kHz, 0.07% THD
................................................................80W
REAR L/R
8 ohms,
20 Hz to 20 kHz
, 0.07% THD
......................................................80W+80W
 

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As long as you don't play it at '11' all the time - no. Speakers are more susceptible to damage when you use an under powered amp - especially when you 'clip' the amp. The worse the clipping the more the signal the speaker sees a DC current which heats up the voice coil (motor).
thanks knucklehead
 

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As long as you don't play it at '11' all the time - no. Speakers are more susceptible to damage when you use an under powered amp - especially when you 'clip' the amp. The worse the clipping the more the signal the speaker sees a DC current which heats up the voice coil (motor).
The common conception that "speakers damaged by under powered amp" is a myth. Speakers are damaged by heating of the voicecoil. That damage occurs when the RMS (heating value) of the applied signal is too high. It doesn't matter that the RMS value is caused by a clipped signal or an unclipped signal.

If you start with an unclipped sine wave at 10 watts, then up the level 10dB so that it's clipped severely, the result is a 10dB change in RMS value, the same as if you raised the level 10dB without clipping.

As far as tweeters are concerned, if there's a crossover involved there's no applying DC to the voicecoil as there's a capacitor blocking it. Any DC component of any waveform is also blocked.
 

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It's not the DC. It's the high frequency crud that's generated at FULL POWER when the amp clips. The crud goes straight to the tweeter and "poof".
That's what would seem logical, but that's also not how it works. When you clip audio, as in music, the actual spectral distribution doesn't change a lot, but the RMS level does go up. It doesn't go up much differently than if you just changed the level without clipping, though, until you get into severe clipping. The effect is of course dependant on the music itself.

These are kind of hard to see, but it's a contemporary tune, which I chose because contemporary music is more dense and would clip more often. The lower plot pair is L/R without clipping, the upper plot pair is the same tune pushed 10dB past the clipping threshold. Notice the spectral distribution is nearly identical. This would not be true of a sine wave where no harmonics exist at all without distortion, but with the spectral distribution of music itself the actual contribution of the added harmonics is not easily seen. But you can see there is no high frequency content that is substantially different from the unclipped spectrum below it.

The detector algorithm in the spectral analysis is not true RMS of course, its an average, but the difference with this kind of signal won't be all that great.

The explanation is that clipping is a peak related function, and while it definitely adds harmonic content, that content is below that of the unclipped waveform, and is also distributed temporally, meaning it's not there for very long (existing only as long as a peak is clipped). So from the standpoint of RMS heating, it doesn't change the spectrum in complex signals.

The other thing is, 10dB is a LOT of clipping, something nobody would actually tolerate for very long. 3dB is actually a lot too, still very nasty sounding. The typical peak clipping people worry about in terms of blowing speakers isn't even 3dB, at least not for more than a brief instant, because audio pushed that far into clipping is simply unlistenable.

The RMS change is what's interesting. With just a few dB of clipping, the difference between a clipped signal and an unclipped signal with the same level increase is very small, if any. However, at 10dB of clipping, the difference is noticeable, with the RMS level of the clipped signal becoming higher sooner. However, this effect is highly program dependant, and as such there's no real way to generalize.

What we can say is that the heating caused by nominally clipped audio is no worse than unclipped audio of the same RMS level. In fact, the unclipped may be slightly more dangerous because it is not limited in maximum peak level like a clipped signal. The situation may change if there is gross and continuous clipping, or if the audio itself is pre processed for very high density.
 

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One caveat: a lot of amplifiers clip asymmetrically, which can introduce a non-zero mean output signal that looks like DC riding on the signal.

Clipping of 3 to 10 dB does not surprise me but such peaks tend to be brief. RMS over time is the culprit in heating... Sustained clipping can go unnoticed depending on the type of music and amount of background noise (or alcohol imbibed) and can put a lot more power into the tweeter than expected, but the really big clipping signals tend to be very LF since that's where all the power goes (see loudness curves). I wrote up some illustrations over on WBF showing various degrees of clipping, including some (very short) sound files to let you hear what clipping sounds like.

There are a number of failure mechanisms in speakers, short and long term, mechanical and electrical. Voice coil overheating can melt wires or glue (causing delamination), a big spike can cause mechanical damage to the spyder or surround, heat can degrade the magnet and degrade the driver's efficiency and performance, continual flexure can break the little wires connecting the terminals to the voice coil, high power causes modes in the cones that can lead to early cone failure, etc. etc. etc. I have seen a lot of ways speakers can be destroyed but am not a speaker expert so leave it to them to better explain.
 

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That's what would seem logical, but that's also not how it works. When you clip audio, as in music, the actual spectral distribution doesn't change a lot, but the RMS level does go up.
Incorrect...
Whenever clipping occurs, two things happen:
1. The spectral content of the music signal is altered significantly as high frequency components are generated
2. Signal compression occurs, raising the amplifier's peak output voltage swings


Just my $0.02... ;)
 

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Incorrect...
Whenever clipping occurs, two things happen:
1. The spectral content of the music signal is altered significantly as high frequency components are generated
Correct, but in practice the high frequency components added are well mixed with the existing spectrum. You did see the image I posted, right? It's a spectrum plot of a signal where the maximum peak exceeds the clipping threshold by 10dB, as compared to an unclipped version of the same signal where the maximum peak is just below the threshold of clipping.

To actually see the result of the harmonics added by clipping you need to start with a pure sine wave.
2. Signal compression occurs, raising the amplifier's peak output voltage swings
Incorrect. The maximum peak output voltage is solidly fixed. That's what causes clipping in the first place. It's the RMS level goes up, as I said before. Clipping is not signal compression. It's clipping, which is very different.
 

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One caveat: a lot of amplifiers clip asymmetrically, which can introduce a non-zero mean output signal that looks like DC riding on the signal.
Unless we're talking about gross and excessive clipping, asymmetrical clipping doesn't inject a variable DC bias any more than an asymmetrical human voice does. Assuming of course reasonable amplifier design.

I've only seen one example of really bad asymmetric clipping, but it was a rather ancient solid state design with a single pole power supply that depended on an artificial reference between ground a Vcc, and of course a HUGE output cap to block the half-power supply voltage DC that came pouring out of the thing. Typically in todays SS designs there's a bipolar supply, the output is DC coupled, and ground is the zero reference, so it's not usually an issue. But even if one rail were reduced in voltage causing asymmetric clipping that wouldn't impress any DC on the signal, it would just clip asymmetrically.

Of course, I don't measure as many amps as I used to, perhaps the Class D and T stuff does weird things.
 

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A non-zero mean is not the same as a D.C. bias voltage. I have seen D.C. bias voltage imposed at the output but that usually means the output device(s) shorted to the rail of a D.C.-coupled output stage... And I have only rarely seen the asymmetry be very bad; usually it is the result of differences in device characteristics and biasing and is relatively small.

Clipping in Class D is a totally different beast though the result is pretty much the same. I am not sure what Class T is though IIRC it is a variant of Class D.

One other issue not discussed are those designs poor enough to become unstable when clipping.
 

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One other issue not discussed are those designs poor enough to become unstable when clipping.
Yeah, glad you mentioned that one. I thought of that when I was away from the computer today. Ever seen an amp break into oscillation when it clips? I'll be you have, and that actually could in fact blow tweets. Ultrasonics are never good. I saw one (years ago!) enter clipping cleanly than oscillate out of it all the way to zero. I just thought those days were over.

Class T is just a trademark for a variant of Class D. Google Tripath amplifier.
 

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Correct, but in practice the high frequency components added are well mixed with the existing spectrum. You did see the image I posted, right? It's a spectrum plot of a signal where the maximum peak exceeds the clipping threshold by 10dB, as compared to an unclipped version of the same signal where the maximum peak is just below the threshold of clipping.

To actually see the result of the harmonics added by clipping you need to start with a pure sine wave.
Incorrect. The maximum peak output voltage is solidly fixed. That's what causes clipping in the first place. It's the RMS level goes up, as I said before. Clipping is not signal compression. It's clipping, which is very different.

Well kinda rite...
Really depends upon the amplifier's power supply design and regulation...
Since most power supplies used in consumer amplifiers/receivers are loosely regulated as to provide maximum peak output power.. When clipping occurs the power supply is spiking resulting in high & abrupt peak voltage swings.. Very visible with an oscillscope..
This is easily seen if one measures the amplifier's output peaks while the clipping occurs.. Again this is more apparent in consumer products as the higher end/quality component & pro amplifiers have better regulated power supplies and protection circuitry..

Being in the audio business for many years, this is one of the primary reasons loudspeakers are taken out and returned for warranty replacement. However to control the product returns we actually take apart some of the returned drivers and clearly the abuse is apparent and cause for failure...

Just my $0.02... ;)
 

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Yeah, glad you mentioned that one. I thought of that when I was away from the computer today. Ever seen an amp break into oscillation when it clips? I'll be you have, and that actually could in fact blow tweets. Ultrasonics are never good. I saw one (years ago!) enter clipping cleanly than oscillate out of it all the way to zero. I just thought those days were over.
Yes, many times, and not just audio amps (since most of my career has focused on GHz and mW stuff). As for those days being over, don't bet on it... ;)

Class T is just a trademark for a variant of Class D. Google Tripath amplifier.
Thank you.
 
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