Electronics > Projects, Designs, and Technical Stuff
Yet another Audiophile Question.
Bassman59:
Think about what causes driver destruction.
First, there's the obvious -- over-excursion. A too-loud impulsive sound like snare drum or the cannon shot from the "1812 Overture" that's well above the average level of the music launches the driver out -- and never to return in. Ooops.
But the most common mechanism for driver failure is thermal overload. Too much power. Area under the curve.
It's common to think about audio power amplifiers as being "power" devices, because their outputs are given in watts and all of it. But they are really voltage amplifiers that can source or sink a lot of current.
This means that there's an upper limit to an amplifier's output, which is the supply rail. Hit the rail and you clip, we all know that, right?
What happens when you clip a signal? The simple answer is that the output stays at the rail for the duration of the time that the input voltage times the gain wants to exceed the rail (plus, perhaps, an overload recovery time).
And all of the time sitting at the rail means you're just dumping current, in a DC sense, into the voice coil and you're baking it.
The amplifier with the higher voltage rails ("more power") would allow a higher-level output to go through unclipped, and because real music waveforms don't sit at a peak for very long, a peak doesn't damage the driver because it's not generating enough heat to do so. The amplifier with the lower voltage rails ("less power") clips and stays at the rail and thus a constant voltage level, generating more heat in the voice coil and eventually the driver dies.
Area under the curve.
As for the Klipsch minimum-power recommendation, it's silly. As long as the amplifier output is clean, not clipped, a 5 W amplifier won't damage the speakers.
TimFox:
Going back to my serious suggestion on how to determine quantitatively the amplifier power you need.
This can be simplified: start by playing your typical CDs and note the highest volume control setting you used to get the desired sound level for your personal taste.
Then do my suggested measurement of amplifier output vs. input voltage at that setting, assume the peak level input is the CD player rated output, and that will give you (by careful algebra) how much peak power you were using. That would represent a minimum power that you actually need.
The basis of this method is the well-defined peak output of the CD player.
bson:
There are few absolutes though. Most commercial amplifiers sold have soft-clipping circuitry, exactly to protect speakers (and prevent sonic artifacts).
Class D amplifiers can boost their output above their supply voltage - part of why they're so great on battery power.
tooki:
--- Quote from: bson on August 06, 2020, 03:06:13 am ---Class D amplifiers can boost their output above their supply voltage - part of why they're so great on battery power.
--- End quote ---
Well, a few can, especially newer ones with purely digital inputs. But when researching this topic earlier this year, I was surprised to learn that the vast majority of class D amps require high voltages for high outputs. I looked at the designs of a few Bluetooth speakers and found they used boost converters to create the supply voltages for the amps. I couldn’t find any analog-input class D amps with more than a couple of watts output power that could do so on low voltages.
Conrad Hoffman:
IMO, their response was just plain wrong. @Bassman59 gets right to the heart of the matter- it's area under the curve. Though not widely understood/accepted, the whole "clipping causes high frequencies that blow tweeters" myth is just that. The idea that clipping creates high frequency signals sufficient to blow tweeters doesn't work out when you do the math. What happens is if you're running at a high enough level to clip badly, you're running too loud and the tweeter is overloaded regardless. A high power amp at the same level, sans clipping, would blow the tweeter as well. Area under the curve. Audio is so full of misinformation you really need to study basic electronics, not "audio electronics."
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