Speakers blown from being too large...

[McGarnigal]

People on this board always mention how you can actually blow your speakers from being too quiet or having a receiver that doesn't deliver enough power. I was just wondering if someone could explain the technical science behind that fact. Thanks.

[Rob J in WNY]

One factor in the equation is that, with lower-powered amplifiers, there can be a greater danger of burning out speakers. Here's why.

Increasing sound volume is an increase in amplitude. In basic terms, audio output from an amplifier is an alternating current (A/C) signal. Think of a pure sine wave tone (which we will use for the sake of example). The "peaks" and "valleys" of the sine wave get taller as amplitude, or volume, rises.

With smaller amplifiers, continuously turning up the volume eventually causes the amplitude to hit its limit sooner than with larger amplifers. What then happens is that, with regard to our "sine wave" example, we actually cannot gain any further amplitude, so the peaks and valleys of the waveform cannot become any larger. Our sine wave is maxed out, and the peaks and valleys become "clipped" causing our smooth, A/C audio momentarily becomes a direct current (D/C) signal. When you hear of an amplifer being driven to "clipping," this is what is being referred to.

D/C voltage is particularly dangerous to the fine voice-coil structure in speaker drivers - especially tweeters. The coils overheat from the sustained D/C voltage, and their fine wire can either break (opening the speaker wire circuit) or else melt together, ruining the motive magnetic relationship with the magent structure. Usually accompanied by that burning smell!

While you can certainly "blow" speakers by applying too much "clean" power to them, smaller amplifiers driven too hard are a far larger danger. You can easily burn out 200 watt speakers with a 20 watt-per-channel amp driven to horrible "clipping" levels.

These are words to the wise. It's fun to drive our HTs to the max, but there is a danger in doing so, especially because there is almost always audio dynamics which seem to sneak up on us that will send an amplifer over the top. Know the limits and be careful with those (fun) demonstrations. As an example, with only a 6dB audible gain in perceived volume, and amplifer is demanded 4X the wattage. That's the difference between an average output of 50 watts to about 200 watts - many common HT receivers are rated for around 100 watts per channel, and peak program material, if sustained, will overtax an amplifier's "headroom" and cause voice-coil-threatening high-level D/C voltage.

Hope that helps!

[worldturning]

Well...could be a myth???

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

An excerpt:

- If your speakers are capable of handling significantly more than your amplifier can produce, driving them with a clipped signal will not likely hurt them.
- If the speakers can handle 3 or 4 times the power that your amplifier can produce, there's virtually no way to damage your speakers (no matter how clipped the signal is).
- If your speakers are rated for the same power handling as your amplifier is capable of producing cleanly, driving them with a clipped signal for extended periods of time may cause speaker damage and/or premature failure.
- If your speakers are rated for the same power handling as your amplifier is capable of producing cleanly, driving them with a square wave signal for extended periods of time will likely cause speaker damage.


http://www.gmtruckhq.com/sound-secur...s-did-959.html

Excerpt:

DC in clipping. One of the most famous myths regarding clipping is that it produces DC. The assumption is made because of the flat tops and bottoms to a square wave. It's incorrect to think of a squarewave as made up of positive and negative dc components. The only way for a it to be DC would be if there was a non-zero average value over long periods of time. If the polarity changes at all within the time frame that you are looking at, it is simply not DC. What are these flat portions of the signal? It is simply a combination of the fundamental frequency and all of it?s higher order harmonics in sine wave form.

And:

...there are only two ways to damage a speaker: Mechanically and Thermally. The only way to do this is by applying too much input power in a given enclosure (mechanically) or too much average power over time (thermally). There is no DC in a clipped signal; the coil does not stand still; air passing over the coil (and thus cooling) is the same regardless of the waveform; and clipping is acceptable provided that the average power over time is lower than the speaker?s limits. The next time you hear those famed words ?your speakers died because of clipping?, remember what you have learned, and above all, keep searching for the truth?.it?s out there somewhere.


Even Monster Cable has a white paper:

http://www.monstercable.com/mpc/stab...Some_Facts.pdf

Excerpt (basically backs up the previous two links):

It is sometimes claimed that a good way to prevent speaker damage is to use a larger amp. This is true only if you don't turn the larger amp up until you exceed the average power to the speaker. A larger amp will allow for the larger transient peaks to be reproduced without damage to the speaker because the total heating of those short peaks is minimal anyway. This will almost always result in a cleaner sounding system. But if you continue to increase the power to the speaker until the average power is excessive, then it doesn't matter if the signal is clean or distorted ---- the speaker will overheat and burn up. Usually when this is done the speaker will begin to distort before the amplifier. If this happens this is a sure sign that you are feeding the speaker too much power.

When considering speaker power ratings and amplifier size it should never be forgotten that although amplifiers are usually rated with continuous sine waves, speakers rarely are. When matching amplifiers and speaker power ratings you are literally comparing apples and oranges. This should not normally be a problem as long as we remember how the ratings differ.

The most efficient woofers rarely exceed even 2%. If we put 100 watts of power into a speaker, this means less than 2% of the power is turned into sound and over 98% of the power is turned into heat. The next time you need to be reminded of how much heat 100 watts is just grab a glowing 100-watt light bulb. And just think, not all of the energy if alight bulb is turned into heat, in fact they are more efficient than most speakers!

If your speaker were fed 100 watts continuously it would have to dissipate this much heat from its coil. Not many speakers are really designed to handle 100-watt continuous sine waves, but when rated for dynamic music that is constantly changing (providing cooling periods), a speaker that can only handle perhaps 50 watts continuous sine waves can easily deal with the undistorted output of a 400-watt amp. That's because the average output of that 400-watt amp reproducing undistorted music is probably not over 50 watts.

If you can keep things under control you will be safe with the 400-watt amp. The same speaker that can handle 50 watts of continuous sine waves can probably deal with 100 watts of a totally distorted amp.

In nearly all cases when we see power ratings on a speaker, the manufacturer has taken into account that you are going to be playing music on that speaker. That is why we see ratings on some small tweeters as high as 100 or even 200 watts. This usually means that if the amp is about the same size and not allowed to distort, then the average power will be about right.

It is not that distortion hurts speakers; it is just that distortion is usually a sign that something is too loud. This is also why we can find examples of 300, 500, and even 1000-watt woofers. You can be sure these are not ratings for continuous sine waves, continuous music maybe, but not sine waves. Next time you think you have a 1000-watt woofer, think about the heat produced by your hair dryer and imagine that much heat building up in a small box in the back of your car ---- better get a fire extinguisher!

Originally Posted by McGarnigal

People on this board always mention how you can actually blow your speakers from being too quiet or having a receiver that doesn't deliver enough power. I was just wondering if someone could explain the technical science behind that fact. Thanks.

[Opips2]

My integrated amplifier stereo is 55 watts outputs to 100 watts. If turn higher volume loudest can burn a speaker but you listen to good sound loud. That’s fine. I love it

Receiver is poor sound audio because it‘s not balance high/low sound!

Amplifier is high audio sound because advance sound and never low sound.

[chriharr]

Originally Posted by Rob J in WNY

One factor in the equation is that, with lower-powered amplifiers, there can be a greater danger of burning out speakers. Here's why.

Increasing sound volume is an increase in amplitude. In basic terms, audio output from an amplifier is an alternating current (A/C) signal. Think of a pure sine wave tone (which we will use for the sake of example). The "peaks" and "valleys" of the sine wave get taller as amplitude, or volume, rises.

With smaller amplifiers, continuously turning up the volume eventually causes the amplitude to hit its limit sooner than with larger amplifers. What then happens is that, with regard to our "sine wave" example, we actually cannot gain any further amplitude, so the peaks and valleys of the waveform cannot become any larger. Our sine wave is maxed out, and the peaks and valleys become "clipped" causing our smooth, A/C audio momentarily becomes a direct current (D/C) signal. When you hear of an amplifer being driven to "clipping," this is what is being referred to.

D/C voltage is particularly dangerous to the fine voice-coil structure in speaker drivers - especially tweeters. The coils overheat from the sustained D/C voltage, and their fine wire can either break (opening the speaker wire circuit) or else melt together, ruining the motive magnetic relationship with the magent structure. Usually accompanied by that burning smell!

While you can certainly "blow" speakers by applying too much "clean" power to them, smaller amplifiers driven too hard are a far larger danger. You can easily burn out 200 watt speakers with a 20 watt-per-channel amp driven to horrible "clipping" levels.

These are words to the wise. It's fun to drive our HTs to the max, but there is a danger in doing so, especially because there is almost always audio dynamics which seem to sneak up on us that will send an amplifer over the top. Know the limits and be careful with those (fun) demonstrations. As an example, with only a 6dB audible gain in perceived volume, and amplifer is demanded 4X the wattage. That's the difference between an average output of 50 watts to about 200 watts - many common HT receivers are rated for around 100 watts per channel, and peak program material, if sustained, will overtax an amplifier's "headroom" and cause voice-coil-threatening high-level D/C voltage.

Hope that helps!

It's almost the same method as AC Power, e.g. plug in a 8,000 watt device into a mains outlet that supports a max load of let's say 4,000 watts, a short happens which either blows the device up or badly damages everything connected in the area by the mains.

under powering a device has the same effect.

[Blu-Dog]

Originally Posted by Rob J in WNY

Hope that helps!

Terrific explanation, well said.

[worldturning]

Originally Posted by Blu-Dog

Terrific explanation, well said.

But is it accurate???

I'm not an expert by any means, but from various articles, the "clipping" amplifier/receiver is one of the most repeated myths in audio.

It is the continuous average power over time that leads to the speaker failing when that average power is greater than the "clean" wattage that the speaker can handle.

[Blu-Dog]

Originally Posted by worldturning

But is it accurate???

I'm not an expert by any means, but from various articles, the "clipping" amplifier/receiver is one of the most repeated myths in audio.

It is the continuous average power over time that leads to the speaker failing when that average power is greater than the "clean" wattage that the speaker can handle.

I've blown speakers with higher ratings than the crappy car stereo head units they were connected to - and I trusted the power ratings (JBL and Audiobahn gear). It may be a myth, but I don't know what any other explanation would be in the circumstances I've seen.

Clipping a driver results in heat. It wouldn't cause a spectacular "blowout", but eventually a tortured driver will fail, if not well designed for heat dissipation. My theory, anyway - based on paranoia from watching drivers fail.

I could be wrong.

[worldturning]

Originally Posted by Blu-Dog

I've blown speakers with higher ratings than the crappy car stereo head units they were connected to - and I trusted the power ratings (JBL and Audiobahn gear). It may be a myth, but I don't know what any other explanation would be in the circumstances I've seen.

Clipping a driver results in heat. It wouldn't cause a spectacular "blowout", but eventually a tortured driver will fail, if not well designed for heat dissipation. My theory, anyway - based on paranoia from watching drivers fail.

I could be wrong.

Just to clarify from my previous post, clipping is not the myth. The so called myth is that the amplifier clipping causes the speakers to fail.

I re-edited my post#3 to show excerpts from the links.

I could be wrong too. Just thought that it was interesting that there was an opposing view which may have some actual science behind it.