For the last time, PLEASE: clipping does NOT blow speakers/subwoofers

[psych0ticnemes1 5,000+ posts]

If you'd like a good article that is much more in depth, here is one that Richard Clark wrote. http://www.monstercable.com/mpc/stable/tech/A2420_Some_Facts.pdfHere's the part that's important to this thread:

"The

total energy represented by both tracks is exactly the same and will produce virtually the same heating

effect in the voice coil of a speaker. The speaker doesn't care if the music is distorted or not. To a

speaker it is all just a combination of sine waves. A speaker cannot tell the difference between noise,

distortion, or music. It doesn't care what kind of music it is or any thing else about it except how much

energy is contained in the signal."

Even better. That makes sense. In other words, if I wanted to turn my bass boost or gain up to send more power to my woofer, it would distort the sound but it wouldn't damage the sub until it reached the sub's mechanical or electrical limits.

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[audioholic 5,000+ posts]

I should also mention that if distortion was so bad for speakers then everybody that listens to Soulja Boy would instantly fry their speakers //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Distortion inherent to the recording is treated like just another musical note to the stereo. In other words, when Aerosmith intentionally distorts their guitar amps for that 'warmth', and you play that song, you think your amplifier is outputting square waves? Its not. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[Lakota 5,000+ posts]

Distortion inherent to the recording is treated like just another musical note to the stereo. In other words, when Aerosmith intentionally distorts their guitar amps for that 'warmth', and you play that song, you think your amplifier is outputting square waves? Its not. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

Well, the purpose of an amplifier is for the input and output signals to have have the same characteristics (shape), but for the output to have a larger magnitude. If it doesn't then there is distortion of the original signal. It is a linear relationship.

 

[mil81 10+ year member]

The current is not technically DC when the top of a sinusoidal wave is clipped off, it just has a slope of 0 for that period. The wave is still alternating between positive and negative, thus still being AC. The change is in the waveform itself, not its direction.
When you send DC to a sub the sub will just move into the direction of the applied voltage, i.e. up if wired in phase and down if wired 180 degrees out of phase. The sub will not move both up and down because the current isn't alternating between positive and negative (has no frequency).

Here's some proof from Rockford Fosgate themselves. It is explained in the last paragraph. http://www.rockfordfosgate.com/scripts/rightnow.cfg/php.exe/enduser/std_adp.php?p_sid=FQNNCi4j&p_lva=&p_faqid=63&p_created=965346111&p_sp=cF9zcmNoPTEmcF9ncmlkc29ydD0mcF9yb3dfY250PTkmcF9zZWFyY2hfdGV4dD1kaXN0b3J0aW9uJnBfc2VhcmNoX3R5cGU9MyZwX3Byb2RfbHZsMT1_YW55fiZwX3Byb2RfbHZsMj1_YW55fiZwX2NhdF9sdmwxPX5hbnl_JnBfY2F0X2x2bDI9fmFueX4mcF9zb3J0X2J5PWRmbHQmcF9wYWdlPTE*&p_li=

I don't understand how that is not DC. It is not alternating between positive and negative. That's why it shows up as a straight line on the scope. I know it's not as bad as sending straight DC, since there is still AC between the DC lines, but it still can't be good for the speaker.

I guess DC might not push the speaker to it's full limit, so that might not mechanically damage the speaker, but I know sending straight DC into a coil that is meant for AC is damaging. It heats up a lot more than alternating the current. I don't remember the exact physics behind it though.

That is a great write up from Fosgate. I can only assume they are correct, it just doesn't make sense to me.

Murray

 

[Lakota 5,000+ posts]

I don't understand how that is not DC. It is not alternating between positive and negative. That's why it shows up as a straight line on the scope. I know it's not as bad as sending straight DC, since there is still AC between the DC lines, but it still can't be good for the speaker.

Like I said the wave is alternating. The shape of the wave doesn't determine if the wave is AC or DC, but rather if it alternates.

 

[mil81 10+ year member]

The shape of the wave does determine if it is alternating. That is what the Oscilloscope if for. It measures voltage vs time. If the voltage doesn't change over a set time, that means there is no alternation. That is DC. In total, if you look at the clipped signal, it is an alternating signal. But if you look at the time that the signal is clipped, that is straight DC. There is no arguing that. I guess speakers can handle it for that short of a time.

It still makes sense to me that enough short bursts of DC over a time will add up and damage the speaker.

 

[PV Audio 5,000+ posts]

The shape of the wave does determine if it is alternating. That is what the Oscilloscope if for. It measures voltage vs time. If the voltage doesn't change over a set time, that means there is no alternation. That is DC. In total, if you look at the clipped signal, it is an alternating signal. But if you look at the time that the signal is clipped, that is straight DC. There is no arguing that. I guess speakers can handle it for that short of a time.
It still makes sense to me that enough short bursts of DC over a time will add up and damage the speaker.

No, this is not true. It is NOT DC power at any point, you can't just switch forms. What you're seeing is that a fully clipped signal has zero slope, BUT, that signal still has a frequency. THerefore, unless you're sending it a signal with a frequency of 0hz, it's AC no matter how you look at it. If the cone goes in and out, it's AC. If it goes out or in and stays there, then it's DC.

 

[newusername 10+ year member]

I don't understand how that is not DC. It is not alternating between positive and negative. That's why it shows up as a straight line on the scope. I know it's not as bad as sending straight DC, since there is still AC between the DC lines, but it still can't be good for the speaker.
I guess DC might not push the speaker to it's full limit, so that might not mechanically damage the speaker, but I know sending straight DC into a coil that is meant for AC is damaging. It heats up a lot more than alternating the current. I don't remember the exact physics behind it though.

That is a great write up from Fosgate. I can only assume they are correct, it just doesn't make sense to me.

Murray

Familiar with the Fourier Transform? You can easily break that square wave down in to its AC components, with no DC present.

The question arises: is it not DC during the zero slope portions of the signal? This is a question of semantics where we must first define a window. If you accept a very small window in which there is no alternating polarity, then yes, we could say this is representative of DC. However, logic says this is pointless. Imagine, if you will, a square wave with a frequency of 100 Hz. In order to accept this as DC, we would have to use a window of no more than 1/200th of a second (as anything larger would have a change in polarity). Is such a window of any merit? We can also see that our window becomes smaller as frequency increases, and thus it becomes increasingly irrelevant.

Make no doubt about it: there truly is no DC present.

 

[jeremiah 10+ year member]

man this is good to know

 

[PV Audio 5,000+ posts]

man this is good to know

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[audioholic 5,000+ posts]

Well, the purpose of an amplifier is for the input and output signals to have have the same characteristics (shape), but for the output to have a larger magnitude. If it doesn't then there is distortion of the original signal. It is a linear relationship.

When you are describing distortion that has been added to the original recording (presumably on purpose), the amplifier will simply reproduce the sound, it will not make the amplifier automatically output a square waveform.

 

[PV Audio 5,000+ posts]

When you are describing distortion that has been added to the original recording (presumably on purpose), the amplifier will simply reproduce the sound, it will not make the amplifier automatically output a square waveform.

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[newusername 10+ year member]

I agree with Lakota; distortion (whether it is generated by the amplifier or present in the original signal) will increase the average power over time. Of course, this doesn't mean that it is a square wave as all the requisite harmonics would need to be present to do so.

 

[audioholic 5,000+ posts]

I agree with Lakota; distortion (whether it is generated by the amplifier or present in the original signal) will increase the average power over time. Of course, this doesn't mean that it is a square wave as all the requisite harmonics would need to be present to do so.

So how would it generate more heat over time? To the amplifier, its just another sound in the signal to be amplified.

 

[mil81 10+ year member]

Ok, so I got curious.

When I went home for lunch, I took my "high end" stock Infinity speaker that I took out of my Dodge. I hooked it up to a AAA battery. I only had the patience to hold it there for about two minutes. Whatever the case, in that time, I didn't smell any burning voice coil like I would have expected, so I have to admit defeat on this one.

School was a little while ago, but I understood that DC of any sort would hurt a coil. But that doesn't make sense since you have inductive circuits in the DC world. Whatever the case, if I had remembered correctly, then I believe a clipped wave would damage the voice coil, but this is obviously not the case. I stand by the rest of my words, minus the part about the voice coil getting damaged.

I'm sorry if I caused any confusion. And thanks for the arguements.

Murray