speakers

[singhal2]

<font color='#0000FF'>what does it mean when a speaker is rated as having a nominal power rating of 100W to 300W (max.) and does it have any bearing on the power rating on the amp being used to drive it? eg. can an amp with a rating of 85WPC rms be used to safely drive a speaker with a rating of 100W nominal power
singhal2</font>

 

[Jack N]

<font color='#000000'>You are quite correct in thinking that these ratings are a guide to amplifier power.  However these ratings are a highly suggestive guide at best because of the varied &quot;cleanliness&quot; of different amps.  Generally speaking the first rating refers to how much continuous power can be supplied to the speaker without any problems.  The second rating refers to momentary spikes in power, such as those produced by drums. Contrary to what seems logical, it's better to over power speakers than to under power them.  Why?  Bigger amps are more carefully designed to control speaker movement than smaller cheaper amps.  To give you an example, I personally bought a pair of studio monitor speakers 35 years ago that are rated at 75/150.  I've been powering them with a 170 watt continuous amp that can spike at well over 500 amps.  The speakers are still alive and doing well because the amp produces a very clean signal.  The amp's total harmonic distortion is rated at .002%  and the damping factor is over 200 (Note: There is NOT an industry accepted method of determining damping factors so the ratings aren't set in stone).  A clean signal is the single largest factor to speaker longevity.  Even the best speakers will die if fed a diet of poor signal.  So just make sure you know how clean the signal is, and don't go overboard with the power.</font>

 

[Yamahaluver]

<font color='#0000FF'>As long as your amp is not shutting off and you are not driving it to clipping volume, your speakers should be fine, I would worry if your current amp is unable to fill your room and sounds real strained at higher volumes, it is then I would start thinking of an amp upgrade.</font>

 

[annunaki]

<font color='#000000'>Too much power over time is one of two ways to blow a speaker. The other is mechanical failure (which is usually due to overpowering). Distortion does NOT blow speakers in it's own right. When amplifiers fully clip, or fully distort, they DOUBLE their output power.

Here is an example:
Let us say that we have a speaker with a continuous power spec of 100 watts rms. Our amplifier outputs 50 watts rms power unclipped. If we fully clip the amplifier it will only do 100 watts rms power. The speaker, if it's power handling specs are accurate, will NOT blow. We are not exceeding it's continuous power spec or it's cooling capability of the voice coil. Assuming odd order distortion artifacts do not drive the cone, coil, or suspension components past their limits, the only bad thing happening here is the sound of a fully clipped signal.

Now let us say we have the same 100 watt continuous speaker and a 100 watt continuous amplifier unclipped. If this amplifier is driven into full clipping/distortion, it will output 200 watts of power into our 100 watt continuous speaker. Needless to say if this is kept up, over time, we will surely have a voice coil failure, suspension failure or both.

Agian, we have our 100 watt rms speaker. This time we have a 200 watt rms amplifier. If our 200 watt amplifier is driven to full UNCLIPPED/UNDISTORTED output for a long enough time, agian we will have a voice coil failure, suspension failure or both. Reguardless of this amplifier being clipped or unclipped, if it plays long enough at these power levels our poor 100 watt speaker will fail.

Remember that music is dynamic. A speaker may seem totally fine with more than rms power and may sound even slightly better than with it's recommended rms power. However, if the continuous power with music playing exceeds the rms rating of the speaker for too long, it will fail.

Sorry for the long post but there is much disinformation spread about how speakers &quot;blow becasuse of distortion&quot;. I just thought this needed a little clarification. It is better for SOME LISTENERS to overpower speakers, but definitely not a rule of thumb for all.  

The best thing to do is make sure your amplifier outputs what it claims to and stick to the speaker manufacturer's power recommendations.

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[av_phile]

While I can agree with Anunaki in some regards, I can say with certainty that there is real danger in driving speakers with distorted signals coming from an underpowered amplifier. For sure they won't blow your speakers off their suspension, or burn woofer coils to a crisp - something that would easily result from too much current drive from an overpowering amp, but clipped signals from low powered amps driven to the max are very insiduous, often leaving the listener wondering why the catatrophe.

While it is possible not to damage a cone midrange or woofer, the tweeters are often the first to fry. Remember that distorted signals have huge amounts of high order harmonics that goes beyond the fundamental frequencies. And these harmonics can bleed into the tweeters which are most sensitive to clipped signals. Remember also that in a 2-way speaker system of say 100watts handling ability, the two drivers are not identically rated at 100 watts. No speaker manufacturer would do that knowing fully well that the mids and lows will extract about 70% of the amp's power more demandingly than the highs will. Thus, many tweeters in a 100watt speaker system are usually rated at only 30watts. I've seen 3-way 100watt speakers systems with just 20-watt tweeters. And because of this, the mids and lows receiving clipped signals would have clipped odd and even order harmonic content that the crossover networks will route to the poor tweeters and promptly do damage there.

I've come across damaged speaker systems whose problems are fried tweeter voice coils. Asked what happened, the users often can't understand why their 30-watt amp driving a 80-watt speaker did such a damage. Further investigation revealed they were listening at volume settings in the 3 o'clock position for quite an extended period. That's virtually maxed out. Afterall, they reasoned their speakers should very well handle their 30-watters. Well, i had to make about the same explanation as above. Under such a condition, the amps were actually sending clipped harmonics that exceeded their tweeter's 20-watt patience.

 

[annunaki]

You are correct in the sense of the tweeter usually being fairly low wattage. The ear is much more sensitive in the midrange, and treble areas (500hz-10khz). If using a three way speaker it would be pretty normal to see the mid and tweeter having a lower powerhandling than the systems total power. In some cases it is much lower than dividing the system's power handling by the number of drive units. This is made possible through the internal crossover network.

Severe clipping cannot destroy any driver, reguardless of size, if the clipped power level is within the driver's power handling and mechanical limits. This includes odd order harmonics. Odd order harmonics will not exceed twice the unclipped output of the amplifier. Under full clipping any amplifier will double it's unclipped output power. By unclipped I mean below 1% thd. Some (very few in the home audio arena) manufacturers are not the most honest in reguards to a driver's actual powerhandling. If any one person could drive their speakers with a fully clipped signal, and like it, they shoud not have audio equipment.

 

[dmoss]

I was always told that you want to use an amp which exceeds the wattage recommendations of the speakers you are using. While a speaker can be damaged by both under and over driving them, I really do think that under driving the speakers or distortion at higher volume levels of the speakers max's are more apt to blow the speaker than running a 200 watt speaker at a clean 250 watts. Again I think descretion must be used, but for my money I will go the bigger amp route. I just bot Paradigms which rate at 220 watts and I purchase an amp that runs 5 channels at 250 watts continuous. I don't think it will be the additional clean 30 watts which could blow the speaker but rather having an amp that runs out of power at 150 watts and then tries to run on up to 200watt creating big time distortion.

 

[annunaki]

dmoss, If using a 150 watt amplifier and it is run to full clipping, one would be looking at 300 watts of clipped power. Which, over time, because it exceeds the power handling of the speaker, would cause it to fail.

With running 30 watts over your speaker's power handling, if left long enough, consistently exceeding the rating by 30 watts, your speaker would fail. Granted, it would take quite a long time, especially with music. (in your case probably at least 10 hours at your amplifier's rms output unclipped/undistorted)

When most drivers are overpowered by say 10%-20% (in rare cases, drivers will not reach power compression until over-powered by say 50%) they start to go into power compression. Power compression is when a speaker stops turning input power into output and wastes it in the form of excess heat. Now that the woofer is wasting this power in heat, and not moving any farther to dissapate it. It simply builds up on the voice coil, typically the windings above the top plate. If the power is not reduced soon after power compression begins, it will not be long until the coil scorches and fails or some type of mechanical failure happens (spider/surround failure, coil leaving the gap, former-neck joint separation, ect.).