Busting speakers

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Hey there. I was wondering, since class D amplifiers are basically just pulsing a signal to the speakers(the MOSFETs either fully on or off), do they have the same tendency to burn out speakers that are rated for a higher power handling as other amps do? For instance, if you drive a 400W driver with a 200W rated amp it will clip and bust the speaker. Does this also apply to class D? I would assume it does, but I'm curious ;-)
 
:nownow:
Usually it is not the amp, but certain people who have tendency to fry the speakers.
This applied to the analogue guys in the 70s as well as it applies to the digital natives of the 2ks. The only thing which can keep ignorant people from frying/busting/bottomingtodeath speakers is a correctly adjusted limiter, which is locked against unauthorized changes.
 
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Horst I think it is very important to make the distiction between underpowering and clipping. Sure if you have an amp that even outputing a square wave will not produce more average power than your speakers can handle then that clipping will not damage the speakers.

However if you have an amp that whilst not clipping is a bit below the speakers power handling ability, but you drive it into clipping, then you almost certainly Will damage your speakers!

This is an extract from Bill's post. Bolding is mine.

Most widely available recordings have a crest factor of approximately 10dB. Looking at this in terms of power, the peak power is 10 times greater than the average power. If we were to play one of these recordings with our 50 watt amplifier when not clipping, the speaker needs to dissipate a mere 5 watts of average power over time. When the amplifier begins clipping, the peak level/power does not increase. BUT, the average power DOES increase. If we were to turn the volume up 6dB higher than the clipping level of our recording, we have reduced our crest factor to 4dB. Guess what? We are now needing the speaker to dissipate 20watts. This is four times the average power and four times the heat when measured over time. As you can see here, it is not the distortion or the waveform or anything along those lines that is killing your speaker; there is simply more average power over time. However, if the average power of time is still below what your speaker can handle, it doesn't matter if it's clipping or not. At higher power levels, the fact that a clipped signal carries more average power over time can result in damage.
as to whether or not having a more powerful amp which will not clip if turned up that extra bit, will result in overpowering the speakers is another matter. What is apparent (from my experience of drunk people at parties) is that the demise of tweeters comes quickly after the volume level is advanced that little bit past clipping. I guess the safest option is to have an amp that when clipping can only deliver slightly less power than the continuous rated power of the speakers (or prevent clipping in the first place, or use speaker protection) :)

Tony.
 
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There are two worlds regarding clipping: a) full-range amp and passive X-over: The additional harmonics when lower or mid frequencies are clipped go through the X-over and can overload the tweeter (and sound ugly too).
b) active X-over and one amp for each driver: clipped signals do not reach the tweeter as long as the tweeter channel itself is not clipped. Clipping e. g. of the bass amp will sound less ugly too - due to the mechanical lowpass of the subwoofer almost no high frequencies are reproduced AND the low frequencies in case of LF amp overload do NOT modulate mid and high - this makes quite a bit of difference. (Intermodulation is what sounds really ugly - pure THD is much more "pleasant".)
In this b)-case I almost go along the line of Bill Fitzmaurice. Some minor errors though:
"If we were to play a sine wave on our 50 watt amplifier, just below its clipping level, the average power over time the speaker would need to dissipate is 25 watts" -> Wrong, it is 50Watts. (with peak power at the sinewave crest being up to 100W or double the average power).
"Our same 50 watt amplifier playing a square wave into our speaker requires the speaker to dissipate 50 watts." Wrong -> (If the amps power supply does not sag) it can actually deliver up to 100W average in square mode. But no more than 100W peak.
 
Hey there. I was wondering, since class D amplifiers are basically just pulsing a signal to the speakers(the MOSFETs either fully on or off), do they have the same tendency to burn out speakers that are rated for a higher power handling as other amps do? For instance, if you drive a 400W driver with a 200W rated amp it will clip and bust the speaker. Does this also apply to class D? I would assume it does, but I'm curious ;-)

Clipping or clean, if it exceeds the ability of the speaker assembly to shed the heat that results, it will fail.
 
A clipping amp can create high frequency harmonics at high power, and cause tweeter damage in a multi-way speaker.

Spent a summer repairing speakers/amps/etc for a pro audio rental shop. Second to mechanical damage, tweeter death was the most common failure mode of a speaker.
 
A clipping amp can create high frequency harmonics at high power, and cause tweeter damage in a multi-way speaker.

Spent a summer repairing speakers/amps/etc for a pro audio rental shop. Second to mechanical damage, tweeter death was the most common failure mode of a speaker.

It does not matter what induces it, clipping, clean power, playing level, etc. It is thermal build-up and the speaker's inability to shed it which usually causes the failure. This is especially true in high-frequency drivers with minimal excursion. Mid to low frequency drivers will fail thermally too but they can also fail mechanically from voice-coil topping or bottoming, surround failure, spider tearing, and so on.
 
In 35 years I have never blown a speaker by over driving it.

I did once fry a speaker when my amp went faulty and put out DC.
The smell was terrible.
Even then the speakers impedance went down to 2 ohms instead of 8 ohms.
So it was only partially fried.
I wouldn't have spotted it except the other stereo speaker kept playing louder by quite a bit.


I have. My Hartke 3500 bass amp fried a Crate Speaker rated for 80 watts in less then 1 hour at normal practice levels. The Hartke was on 2.

I ruined a nice set of 4" drivers with a pioneer 80 watt amp while in the army after about 5 hours of high volume listening. I'm still sad I did that as those were great sounding speakers. They were not distorting, the amp was only 1/3 of the way up.

I have deliberately destroyed cheap speakers on numerous occasions with big amps just to see how long they would last.
 
Just 2 days a go I destroyed one of my 80W speakers with one of my 300W amps.
Amp did never clip (limiters prevent that) and it didn´t *seem* to be that loud, but ear has growing tolerance so after an hour playing the speaker died.
I reconed it at once, so I made the autopsy, like it or not.
The wire was toasted, the epoxy had cooked, crumbled, and let it free, the rest of the speaker was so undamaged (including the aluminum VC form) that if I had wanted I might have rewound the VC using the same form.

"Apparent" volume is a **** poor indication of actual power applied.

My experience was very similar to jsixis' and involved similar elements.
Small World indeed :)
 
In 35 years I have never blown a speaker by over driving it.

...so you are not member of the ignorant party folks?

I have to admit - it took me just 2 years of party until I fried the voice coils of an 6x 12" bass array. Just by good luck the left side was running systematically with 2db less there the bass array survived and so the party could go on.
My comment regarding ignorant people who need to be babysitted by a locked limiter also includes me... :eek:
 
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