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Installing VLC Media Player voids your speaker warranty

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Re: Installing VLC Media Player voids your speaker warranty

#131

Post by ferongr »

anaphor wrote: post #54
donatj wrote: post #13

VLC is incapable of increasing the actual power past 100%, all that is being done is the waveform is being modified to be louder within the allowed constraints. If this wrecks the speaker, any other non-VLCed sound could just as easily, and the speakers are therefore underpowered for the laptops internal amplifier. Class action sounds in order.

Also many mastering engineers do the exact same thing to make the music "louder" because the record label/artists demand it. Maybe Dell should start making popular rock/pop music void the warranty as well.

Well, mastering engineers rarely heavily clip audio (ok, Death Magnetic, but that's an exception rather than the rule). What they do is apply heavy dynamic range compression. Even in cases the signal clips lightly, it probably won't do much damage (if at all) since the peaks are transient.

On the other hand, a movie with lots of low frequency content (explosions and stuff) whose audio is clipping will damage the small full range speakers since most of the audio energy is concentrated at the very low frequencies (where the signal has a lot of power) and the peaks are long.

Re: Installing VLC Media Player voids your speaker warranty

#132

Post by tmoertel »

ferongr wrote: post #47
jbk wrote: post #15

As the main developer of VLC, we know about this story since a long time, and this is just Dell putting crap components on their machine and blaming others. Any discussion was impossible with them. So let me explain a bit... In this case, VLC just uses the Windows APIs (DirectSound), and sends signed integers of 16bits (s16) to the Windows Kernel. VLC allows amplification of the INPUT above the sound that was decoded…

While I don't support Dell's decisions, digital (and analog) clipping can easily damage speakers driven at what is normally their maximum power they can handle, since the resulting clipped waveform carries a lot more energy than an unclipped one.

> ... the resulting clipped waveform carries a lot more energy than an unclipped one.

Is this claim actually true?

My understanding is that if you take a waveform and clip it, the resulting waveform actually carries less energy (think of the corresponding integral), but more of that energy is pushed into the higher frequencies. It's this – the unexpectedly large amount of high-frequency energy – that kills speakers because their crossover networks push it into the tiny, tiny tweeters, and they are utterly unprepared for it.

Re: Installing VLC Media Player voids your speaker warranty

#133

Post by lutusp »

tmoertel wrote: post #132
ferongr wrote: post #47

Earlier quoted context omitted.

While I don't support Dell's decisions, digital (and analog) clipping can easily damage speakers driven at what is normally their maximum power they can handle, since the resulting clipped waveform carries a lot more energy than an unclipped one.

> ... the resulting clipped waveform carries a lot more energy than an unclipped one. Is this claim actually true? My understanding is that if you take a waveform and clip it, the resulting waveform actually carries less energy (think of the corresponding integral), but more of that energy is pushed into the higher frequencies. It's this – the unexpectedly large amount of high-frequency energy – that kills speakers b…

>> ... the resulting clipped waveform carries a lot more energy than an unclipped one.

> Is this claim actually true?

Yes, it is -- but it depends on how we define "clipped".

> My understanding is that if you take a waveform and clip it, the resulting waveform actually carries less energy (think of the corresponding integral)

Only if the clipping reduces the peak value. If you compare a sinewave with a peak value of 1, and a square wave with a peak value of 1, the square wave has a substantially higher average level (with a ratio of pi / 2).

> It's this – the unexpectedly large amount of high-frequency energy – that kills speakers because their crossover networks push it into the tiny, tiny tweeters, and they are utterly unprepared for it.

Yes -- the rate at which the speaker cones are required to move is an additional factor. But for a "clipping" definition that clips by means of trying to exceed the available voltage, these two effects add.

http://i.imgur.com/oE5NFZ9.png

In the above linked image, the red trace is sin(x), the integral for the interval 0 The green trace is what you would get if you simply turned up the volume beyond any reasonable setting -- the amplifier produces a clipped version of the sine wave and the peak value is equal to the supply voltage.

Re: Installing VLC Media Player voids your speaker warranty

#134

Post by anaphor »

ferongr wrote: post #131
anaphor wrote: post #54

Earlier quoted context omitted.

Also many mastering engineers do the exact same thing to make the music "louder" because the record label/artists demand it. Maybe Dell should start making popular rock/pop music void the warranty as well.

Well, mastering engineers rarely heavily clip audio (ok, Death Magnetic, but that's an exception rather than the rule). What they do is apply heavy dynamic range compression. Even in cases the signal clips lightly, it probably won't do much damage (if at all) since the peaks are transient. On the other hand, a movie with lots of low frequency content (explosions and stuff) whose audio is clipping will damage the smal…

I was being kind of tongue in cheek. But you're right, most mastering engineers are competent enough to avoid clipping everything. Although you'd be surprised at the amount of music that has clipping at a few points here and there if you start listening for it (unfortunately audacity doesn't help much here since it will lie about clipping if it's exactly at the max).

Re: Installing VLC Media Player voids your speaker warranty

#135

Post by caf »

humbledrone wrote: post #117
slacka wrote: post #104

Earlier quoted context omitted.

Dell may be using poor quality parts. VLC can also make the sound louder than any other media player that I've used while generating destructive square clipping. The problem is it's too easy to set the volume above 100%. I've done so with the mouse wheel. And I now have a $2000 out-of-warranty laptop with blown speakers. Fixes could include: * Not remember settings above 100% between sessions unless an advanced optio…

Audio is generally handed over to the OS via a format called Pulse Code Modulation. This is a series of audio "samples", which in the Windows case are individual signed 16-bit integers. Typically each second of audio is broken into about 44,100 of these integers. Each integer represents the sound amplitude during a particular 1/44,100th of a second, with a large negative number (-32,768) being a small amplitude and a…

It is not that simple. The speaker is a dynamic system whose response to signals is not memoryless. A speaker that can easily handle a pure 4kHz tone at the maximum amplitude cannot necessarily also handle a 4kHz square wave at the maximum amplitude (a square wave distributes much of its power into harmonics). It is well known that you can destroy speakers just as easily by overdriving the output stage of the power amplifier (which leads to clipping) than by overdriving the speakers themselves.

Of course, Dell could include analogue filtering circuitry to filter out the excess power in inaudible frequencies if they wanted to.

Re: Installing VLC Media Player voids your speaker warranty

#136

Post by fnordfnordfnord »

gamache wrote: post #107
fnordfnordfnord wrote: post #86

Earlier quoted context omitted.

>A square wave has twice the power of a sine wave of identical amplitude. 1.41 x >Playing metal at full volume is not as damaging as playing anything intensely digitally clipped at full volume. The output of the amplifier really ought to be bandwidth limited either as a natural consequence of the components used or explicitly with a filter. It is silly to spend power on things that can't be heard.

Assuming the parent is talking about equal maximum amplitude of the sine and square waves, the square wave RMS voltage will be sqrt(2), or 1.4, times the sine wave RMS voltage. And since power is proportional to voltage squared, the square wave will carry sqrt(2)^2, or 2, times the sine wave power.

Derp, thanks to both for the correction.

Re: Installing VLC Media Player voids your speaker warranty

#137

Post by caf »

lutusp wrote: post #95
KaiserPro wrote: post #79

Earlier quoted context omitted.

Thats what limiters are for. The whole point of hard clipping is that +256 or -256 (or the 16bit equivalent) is below the point at which your speakers, amps, cabling or anything else starts to melt. Speakers/amps should have DC protection builtin.

> Thats what limiters are for. Limiters cannot either distinguish or protect against the technical difference between a sine wave and a square wave: http://i.imgur.com/oE5NFZ9.png The red trace is a normal audio signal that doesn't exceed the dynamic range of the amplifier. The green trace is an example of the kind of signal one gets by turning the volume up way above normal. In a hypothetical speaker of one ohm and…

An analogue bandpass filter could be used. Passing a square wave through such a filter will remove much of the power present at inaudible frequencies. Unfortunately, they also require bulky inductors/capacitors.

Re: Installing VLC Media Player voids your speaker warranty

#139

Post by lutusp »

gamache wrote: post #107
fnordfnordfnord wrote: post #86

Earlier quoted context omitted.

>A square wave has twice the power of a sine wave of identical amplitude. 1.41 x >Playing metal at full volume is not as damaging as playing anything intensely digitally clipped at full volume. The output of the amplifier really ought to be bandwidth limited either as a natural consequence of the components used or explicitly with a filter. It is silly to spend power on things that can't be heard.

Assuming the parent is talking about equal maximum amplitude of the sine and square waves, the square wave RMS voltage will be sqrt(2), or 1.4, times the sine wave RMS voltage. And since power is proportional to voltage squared, the square wave will carry sqrt(2)^2, or 2, times the sine wave power.

Actually, if we look at two half-cycle waveforms, one sine and one square, like this:

http://i.imgur.com/oE5NFZ9.png

(Just the left 1/2 of the graph for this example)

The integral of the sine waveform with a peak value of 1, on the interval 0 x http://www.wolframalpha.com/input/?i=integrate%28sin%28x%29%...

= 2

The integral of the square wave on the same interval is = pi

So the ratio increase in average voltage at the speaker (comparing the sine to the square) is pi/2 = 1.57. The increase in speaker power is (pi/2)^2 = 2.46.

Re: Installing VLC Media Player voids your speaker warranty

#140

Post by fnordfnordfnord »

caf wrote: post #135
humbledrone wrote: post #117

Earlier quoted context omitted.

Audio is generally handed over to the OS via a format called Pulse Code Modulation. This is a series of audio "samples", which in the Windows case are individual signed 16-bit integers. Typically each second of audio is broken into about 44,100 of these integers. Each integer represents the sound amplitude during a particular 1/44,100th of a second, with a large negative number (-32,768) being a small amplitude and a…

It is not that simple. The speaker is a dynamic system whose response to signals is not memoryless. A speaker that can easily handle a pure 4kHz tone at the maximum amplitude cannot necessarily also handle a 4kHz square wave at the maximum amplitude (a square wave distributes much of its power into harmonics). It is well known that you can destroy speakers just as easily by overdriving the output stage of the power a…

>Of course, Dell could include analogue filtering circuitry to filter out the excess power in inaudible frequencies if they wanted to.

It likely isn't necessary as it is probably built into the output amplifier. I have no clue what audio amplifier dell used but here is an example of a typical headphone amplifier IC http://www.ti.com/lit/ds/symlink/lm4881.pdf

If you look on page 9 of the datasheet you'll see its frequency response. The attenuation is > -20dB past 15kHz at best. You aren't going to get much of a square wave above 1.5 kHz, and probably not below if you look at the response of the speaker.

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