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Amp too powerful for cabinet


charic
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[quote name='Mr. Foxen' timestamp='1362933752' post='2006382']
Ipods have a power amp, its easy to clip, its how they drive the speakers in headphones.
[/quote] Er...no...in this case the iPod would be the preamp. I can make a horrible noise by using an iPod in that way but it would only pose a threat to the PA if the power amp driving that was driven into distortion or oscillation. Look at all the bedroom guitarists who thrash their preamps to get massive distortion and never ever blow a speaker, nor are ever likely to - the pre and power amps are completely different. The preamp exists only to bring the incoming signal from the instrument up to a level where it can drive the input of the power amp.

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[quote name='Mr. Foxen' timestamp='1362933954' post='2006386']
How about asking a speaker engineer? Oh wait, one has posted on the subject a whole load of times on this forum, and another has already been linked in this thread.
[/quote] Sure, why not - the answer will be the same if he knows his subject

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[quote name='Wiggybass' timestamp='1362934062' post='2006388']
Er...no...in this case the iPod would be the preamp. I can make a horrible noise by using an iPod in that way but it would only pose a threat to the PA if the power amp driving that was driven into distortion or oscillation. Look at all the bedroom guitarists who thrash their preamps to get massive distortion and never ever blow a speaker, nor are ever likely to - the pre and power amps are completely different. The preamp exists only to bring the incoming signal from the instrument up to a level where it can drive the input of the power amp.
[/quote]

Nope, headphones, passive, powered by ipod, make sound. You can indeed make a horrible clipped sound with an ipod, and that is it distorting, and it won't break a PA speaker. And yes, those bedroom guitarists, and gigging guitarists do get massive distortion and never blow a speaker, because distortion doesn't blow speakers.

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[quote name='Wiggybass' timestamp='1362934062' post='2006388']
Er...no...in this case the iPod would be the preamp. I can make a horrible noise by using an iPod in that way but it would only pose a threat to the PA if the power amp driving that was driven into distortion or oscillation. Look at all the bedroom guitarists who thrash their preamps to get massive distortion and never ever blow a speaker, nor are ever likely to - the pre and power amps are completely different. The preamp exists only to bring the incoming signal from the instrument up to a level where it can drive the input of the power amp.
[/quote]

No I meant the power amp in the ipod. It's probably what? A few hundred milliwatts? It's the EXACT same as the case you're describing of too little power driven into distortion into a speaker that's rated higher than that.


Edit - Also, as has been said, a signal of a given power output that's clipping is the same signal regardless of what's clipping in the signal chain. Hell, it could even be a perfectly clean reproduction of a clipped recording. In our scenario it makes no difference.

Edited by Jack
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[quote name='Mr. Foxen' timestamp='1362934341' post='2006393']
Nope, headphones, passive, powered by ipod, make sound. You can indeed make a horrible clipped sound with an ipod, and that is it distorting, and it won't break a PA speaker. And yes, those bedroom guitarists, and gigging guitarists do get massive distortion and never blow a speaker, because distortion doesn't blow speakers.
[/quote] There's any amount of these things online, but here is one that explains it better than I: http://www.prestonelectronics.com/audio/Speakers.htm

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[quote name='Wiggybass' timestamp='1362934679' post='2006403']
There's any amount of these things online, but here is one that explains it better than I: [url="http://www.prestonelectronics.com/audio/Speakers.htm"]http://www.prestonel...io/Speakers.htm[/url]
[/quote]

It explains it better in that it doesn't say that clipping low powered amps damages drivers.

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This discussion has introduced pre-amplifiers, which are largely irrelevant to the topic as they are merely signal conditioning/shaping units. The only thing that matters here are power ampifiers, since they are the devices that push out power to the speaker. iPoods and all devices that employ some kind of speaker contain power amp, however strong or weak of a signal it is they produce.

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It is too much continuous power that causes thermal death to speakers. It doesn't matter whether the waveform is perfectly clean or fully clipped, all that matters is the average longterm power and how long that's applied for (the longer the time, the less power it takes to reach thermal death, the shorter the time the more power it takes because the speaker has thermal mass which can absorb excess heat before the rate of heat dissipation becomes the determining factor).

However, as the crest factor of typical music is about 14dB (1:25 average:peak power ratio), it's very hard to reach that continuous average power level without clipping an amp, unless what you're putting into it is very compressed or the amp is much more powerful than the loudspeaker's thermal rating.

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