[dpe82]

It's hard to know. Speakers are insanely complex beasts whose electrical reactance changes depending on the signal. To simplify things we use measures like RMS current ratings for amplifiers because if you put a sine wave through a speaker they tend to approximate a resistive load due to most of the load being air, and we use nominal impedance to describe speakers because while even though for something as simple as a sine wave a speaker's impedance can vary 4x from nominal depending on frequency, it at least gives us something we can reliably measure.

Once the signal is more complex than a sine wave things get crazy. The more frequencies in a signal, the harder it is to model the power draw since different parts of a complex curve cause the speaker to act more like the low resistance inductor it actually is. Discontinuities and areas of constant voltage (both caused by clipping) are the worst, and to make things even more fun the amplifier is part of the system and affects things as well.

But assuming you know a lot about the speaker, the amplifier and the DAC you could probably build a model that works well for simple sinusoidal audio, but that doesn't cause problems anyway. All bets are off for anything more complex.

So instead you're left with a few options: buy reasonable gear and don't play crap audio, play crap audio but massively overbuild your system so you lower the risk of getting into the unknowable danger zone that changes depending on what you're playing, or use a bunch of heuristics on a signal and try to distort it in some way so it's less potentially damaging.

The problem with the latter is since you don't know where the line is it's easy to be overzealous and end up distorting lots of stuff you don't need to. Problem with the middle is you either end up with something much larger and more expensive than you need, or you cripple what you have to give you a wider margin of safety. Problem with the first is apps like VLC make it exceptionally easy to accidentally play crap audio. Pick your poison.

Could Dell spend a couple extra bucks for higher quality components and create a wider margin of safety? Probably yes. But at the same time the VLC developers are being reckless by putting a tool into consumers hands that makes it so easy to play potentially damaging audio signals.

Edit: clarifications

[mikeash]

I don't really get this description of mitigations as "overzealous". Sure, there's going to be some margin there, but that's just good engineering. The rev limiter on my car's engine doesn't kick in right at the critical RPM where everything falls apart, but some amount below. My CPU's thermal underclocking doesn't start right at the temperature where the component fails, but some comfortable distance below. You could argue that both of those are "overzealous" protections that cause me to lose out on performance I could potentially have otherwise, and that's true, but good engineering in this case generally means using a safety factor for these things.

I don't understand how you can blame VLC at all. Technically, Dell shipped a tool right on the machine that makes it just as easy to play potentially damaging audio signals. Internet Explorer could just as easily play a WAV file that's been crafted to destroy the computer's speakers. The correct approach is to remove that ability, not blame a tool that accidentally triggers the problem.

[dpe82]

Dynamic audio power limiting introduces a whole host of audio distortions that would cause your computer to lie to you by not playing what you told it to. Your computer lying to you is a problem in principal I think, but specifically if you're doing any kind of sound editing/composition it's a huge problem because now you can't know if what you're hearing represents what you're creating or if your os or sound card has messed with it somehow.

As I mentioned, Dell could turn down the input volume to their amp/speakers. It doesn't totally eliminate the ability for a user to damage their speakers but it also doesn't create any distortions. I would guess that's what their bios update does. It just makes everything quieter for everyone.

I appreciate the principal that userland code shouldn't be able to damage hardware, but I'd much prefer my computer not lie to me. Now, I'm also not opposed to dynamic power limiters in general. In fact, that's exactly what VLC should be using if they insist on letting users crank things past levels that would otherwise clip. It just doesn't belong in the os or hardware.

[mikeash]

Your computer's already lying to you by piping your audio through crappy speakers. Is the distortion actually going to be worse with a limiter in place?

I really don't understand, why do you think this functionality doesn't belong in the OS or the hardware? To me, you're basically saying that you're OK with giving arbitrary web sites the ability to damage your hardware, since that's effectively what that ends up implying.

[dpe82]

For really bad audio, no. For otherwise perfectly fine audio, yes.