to anybody who has blown a speaker:

[tcguy85 10+ year member]

this is something i think everybody here should read if you haven't already.

taken from this thread over on diyma.com http://www.diymobileaudio.com/forum/showthread.php?t=36040&highlight=clipping+explained

which was taken from here

http://www.zedaudiocorp.com/Technical/Amplifier-Clipping.htm

Clipping is the arch enemy of speakers, especially higher frequency drivers. It is probably the biggest cause of speaker failure. Looking at the diagram below which shows a clipped sinewave we see from the time axis that the waveform remains at a high amplitude (either positive or negative) for a period of time which is longer than the time it spends when the sinewave is not clipped.

Amplitude

Time

The result of the speaker cone “spending” too much time at one end of its travel will cause voice coil overheating, deformity of the cone/spider assembly. Another effect of amplifier clipping is that harmonics are generated from the fundamental. Assume a 100Hz wave is being clipped. Harmonics at 200Hz, 300Hz, 400Hz, etc are generated. As the harmonic number increases, its amplitude decreases. The amplitude of these higher frequency harmonics is determined by how hard the amplifier clips at the fundamental frequency.

Because high frequency drivers are fragile as compared to high power low frequency and midrange drivers, they are more susceptible to damage. These high frequency harmonics do not generally damage low frequency drivers but this is not always 100% true.

Let us use a 200 watt amplifier as our example and let it be clipping at say +6dB worth of overdrive. +6dB of overdrive in power terms is calculated from the formula [dB=10 x log to the base 10 x power ratio]. Putting the numbers in the formula yields an answer of 4 times power. So the 200 watt amplifier will “attempt” to put out 800 watts. When an amplifier is hard clipped it puts out essentially a square wave which looks like this:

The area under the squarewave represents power and if one compares this with a sinewave at the same frequency, then it is obvious that the area under a sinewave is much less than the square wave.

Music is not constant in its peak amplitude. The ratio of average power to peak power is in the order of 10-20dB. (10dB = 10 times power and 20dB = 100 times power). I would imagine that modern rock and roll/rap music the value is closer to 10dB. This means that with typical music the average power when using a 200w/ch amplifier is in the order of 20 watts per channel with the peaks rising to 200 watts. Anything higher than the 20 watt average will most certainly push the amplifier into clipping. With this scenario the tweeter in a typical bi-amplified system or one with passive crossovers will receive about 10-15% of the power. So the tweeter’s power is about 20-35 watts with our 200 watt amplifier. This is a lot of power for any single tweeter. But let us assume it is OK with this.

When the amplifier clips the energy into the tweeter is many times greater than with unclipped signals. (Of course the amount depends on the degree of clipping but it has been found that people will listen up to 10dB of clipping ). When this happens the compressed wave (now very close to a square wave) is absorbed by the tweeter (and do not forget about all the harmonics) and at this stage the tweeter goes to “the pie in the sky”.

Low frequency drivers are more tolerant of clipping simply because of their more robust construction. I have however seen many a woofer damaged through been overloaded on a continuous basis.

The above discussions have assumed that the waveform is symmetrical about the zero line. Unfortunately music is not like this. The positive half of the wave may not be the same as the negative half. As an example let us assume that this is so and that the positive part of the wave at time zero is larger in amplitude than the negative half. When the amplifier clips, the area under the positive half is more than the negative half and because square waves are being generated by the amplifier the DC component on the speaker rail will not be zero – as it should be.

Remember one fact. DC is a constant voltage. 10 volts positive DC (ref zero) is just that. If our amplifier was flat to DC and we put in a DC signal the amplifier would simply do it’s job – amplify and the output at the speaker rail would be a larger replica of the input. AC on the other hand is just varying DC. A sinewave begins at 0 volts. It rises at a particular rate (determined by the frequency) to its peak value and then declines to zero and repeats the same thing below the zero ref line. BUT at any given time during the single cycle of the sinewave it has an absolute value. The average is zero. A square wave (clipping!!!!) is similar but not the same. The square wave starts at zero, rises very rapidly to it’s peak value, stays there for a time (determined by the frequency) and then returns to zero and the other half of the cycle is below the zero line. The average of course is zero ONLY if the positive half of the square wave is equal to the negative half.

With music and clipped amplifier the average is not zero and in our example above the speaker rail will tend to move positive DC for the period of that non symmetrical clipped wave. DC on a speaker for a sustained period of time (Constant amplifier clipping) will sustain damage.

Click to read more...

 

[phatcat600 10+ year member]

Hey, good info. What is the simple solution to this?

 

[dragnix 5,000+ posts]

good read, still a bit over my head, but good info nevertheless

 

[dragnix 5,000+ posts]

stupid forum

 

[tcguy85 10+ year member]

simple solution..... get what most would call a "crazy" amount of power. dynamic headroom is what its all about.

this part is the part that i think most people don't understand:

Music is not constant in its peak amplitude. The ratio of average power to peak power is in the order of 10-20dB. (10dB = 10 times power and 20dB = 100 times power). I would imagine that modern rock and roll/rap music the value is closer to 10dB. This means that with typical music the average power when using a 200w/ch amplifier is in the order of 20 watts per channel with the peaks rising to 200 watts. Anything higher than the 20 watt average will most certainly push the amplifier into clipping. With this scenario the tweeter in a typical bi-amplified system or one with passive crossovers will receive about 10-15% of the power. So the tweeter’s power is about 20-35 watts with our 200 watt amplifier. This is a lot of power for any single tweeter. But let us assume it is OK with this.

 

[Side Show 10+ year member]

always better to overpower a speaker than underpowering a speaker

 

[phatcat600 10+ year member]

So get an amp with rated power much higher than your components?

 

[tcguy85 10+ year member]

So get an amp with rated power much higher than your components?

yessir!

 

[DejaWiz 5,000+ posts]

Hey, good info. What is the simple solution to this?

Simple solution is to properly set the gains. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

Dowagiac, MI huh? I went to SMC off Cherry Grove Road back in 95-97. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

Drove everyday from St Joseph in a car that got 8mpg. //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif