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Yet another Audiophile Question.

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tooki:

--- Quote from: Conrad Hoffman on August 06, 2020, 12:18:37 pm --- Audio is so full of misinformation you really need to study basic electronics, not "audio electronics."

--- End quote ---
So true. Very well said.

TimFox:
Also, one should try to answer questions quantitatively based on measurements.  A real A/B blind test is nice in theory, but most reports seem to be along the lines of "I changed this part/tube/speaker and the sound/staging/etc. improved/degraded", although the changeover was far from instantaneous or blind.

robca:

--- Quote from: Bassman59 on August 05, 2020, 09:42:05 pm ---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.

--- End quote ---
I'm confused, sorry. I do understand that a long duration DC signal will fry a tweeter. I'm just confused on why the exact same amplifier with, say, a +-12V rail can damage a tweeter more than the twin with a +-24V rail, assuming the output signals are identical amplitude (hence the 12V one is clipped)

I created two horrible Paint JPGs, showing what I mean. Same signal overall amplitude, in one case clipped at an arbitrary height we can call 12V, another full swing. In both cases, the area under the curve is in red. And in the clipped version, the area under the curve is smaller. More complex waveforms will look similar, unless the recovery time from clipping exceeds the highest audio frequency. But even at 44KHz, that would mean a recovery slower than 22 micro seconds

Is recovery from clipping that slow? Or am I missing something else?

Conrad Hoffman:
As usual, Rod Elliott explains things better than I ever could- https://sound-au.com/tweeters.htm

robca:

--- Quote from: Conrad Hoffman on August 06, 2020, 11:24:19 pm ---As usual, Rod Elliott explains things better than I ever could- https://sound-au.com/tweeters.htm

--- End quote ---
Relevant part here:

A persistent myth in the audio industry is that clipping damages tweeters, so you should use a bigger amp to ensure more headroom so the amp won't clip.  This claim is simply bollocks!  Take the 100W amp described above, and replace with an amp big enough to prevent clipping ... even with the additional 12dB input signal as shown in Figure 7.  Since a 100W amp was just below clipping with an average output of 16W, if we add 12dB that takes the peak amp power to 1.6kW (near enough) and the average power will be 254W.

Do you imagine for an instant that this amp won't blow the tweeters (and everything else) if the input level is increased by 12dB (until it's just below clipping)?  Everything will fail, and usually fairly quickly if the speaker was designed for a 'nominal' 100W input.  It is simply nonsense to imagine that the loudspeaker drivers in a 100W speaker can survive an average power of over 250W and peak power of up to 1.6kW.

Which is exactly why I was confused by the statement that a higher voltage rail will not cause problems. The contrary is true: assuming two identical ideal amplifiers with the same input and amplification factor, one with 12V rail one with 24V rail, the one with 24V rail will blow the tweeter faster

And what the Klipsch rep said is wrong.

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