# MYTH: Clipping causes your amplifier to send DC voltage to your subs



## ChrisB

I can't tell you how many times I heard that clipping will send DC voltage to your subs which will in turn ruin them rather quickly. I recently had 4 Orion HCCA 225 Digital reference amplifiers on my test bench and I measured DC voltage in the millivolt range at clipping with my Fluke 117. Furthermore, there is DC Voltage in the millivolt range at power levels below clipping. 

What gives? Where is this DC voltage that will damage subwoofers quickly?


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## OSN

Some people think that squared off waves are DC voltage for short periods of time before ALTERNATING. :laugh:


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## onebadmonte

OSN said:


> Some people think that squared off waves are DC voltage for short periods of time before ALTERNATING. :laugh:


It's not?


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## [email protected]

Same as ripples in DC current being called AC possibly?


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## onebadmonte

BeatsDownLow said:


> Same as ripples in DC current being called AC possibly?


Whaaaa? Holy smokes, getting this is going to be as bad as trying to understand what the hell was going on in that movie "Inception"


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## OSN

BeatsDownLow said:


> Same as ripples in DC current being called AC possibly?


The answer hinges on: do these ripples cross the x axis?


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## MacLeod

AC, DC....doesnt really matter. Its the big blast of power coming down the line at double or more the amps rated power thats doing the damage!


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## 14642

too much power burns coils. doesn't matter whether it's dc or ac. dc that provides less power than the speaker is rated to handle continuously won't burn the coil. Hook up a 6V battery to even a cheap woofer and leave it. You'll drain the battery, the coil will get warm and that'll be it.


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## sonikaccord

But with DC the coil is also stationary and not cooling itself like it would with AC.


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## ChrisB

sonikaccord said:


> But with DC the coil is also stationary and not cooling itself like it would with AC.


So where is this evidence of DC produced during clipping?

One of my friends had an Elemental Designs amplifier blow and send direct DC to his subs therefore taking them out. Aside from serious malfunction, I have yet to measure any significant DC voltage delivered by an amplifier to the speaker outputs at clipping.


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## SQ_Bronco

sonikaccord said:


> But with DC the coil is also stationary and not cooling itself like it would with AC.


The distance a cone moves is based on the p-p voltage it sees. For a given peak-to-peak voltage, a clipped signal has twice as much electrical energy as a pure sine wave, but the woofer cone will move the same distance (function of p-p voltage) whether it is getting a sine wave or a square wave. Also note, the amount of heat produced by electrical resistance increases with the square of current (joule's 1st law, Q = I^2 * R), so doubling current creates (at least *) 4x the heat dissipation requirement. 

(change temp of the conductor also increases resistance, so it's probably more than 4x).

The primary means to cool woofer coils is air forced across the voice coil by the cone motion. More energy with the same amount of cooling can easily lead to failure. This is clearly not a myth.

Anyway, a square wave is identical to a switched DC signal. ITRW, a clipped signal will probably not really be a square wave, since that would sound like aural sandpaper, but it should be easily visible on an oscilloscope. 

ChrisB, can you please describe your test setup?


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## ChrisB

Iota DLS 55 power supply, Velleman HPS40 oscilloscope to verify clipping, 4 ohm 250 watt resistive loads to save my hearing, and a Fluke 117 set to measure DC voltage at clipping. The Fluke was purchased BNIB December 2010, so I am sure it shouldn't be out of calibration so soon.

EDIT: I also used a 68 Hz test tone.

Regardless, I have been told that clipping produces DC voltage, which in turn damages speakers, by many audio sales associates and I have measured no such thing.


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## SQ_Bronco

ChrisB- one good way to visualize this is to look at a graph of amplifier power output vs THD. Zapco did a great job of this with their c2 series- look in one of the manuals for a picture. Output is basically linear/slightly increasing up to the point the amp clips, at which the THD goes WAY up while "power" output (calculated based on p-p voltage, not current) increases very little.


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## SQ_Bronco

I'm confused- how do you "verify clipping" if you don't see the waveform change? If the waveform changes, there is a DC component of the signal.

The issue may be that the velleman is looking for a constant DC signal, whereas it's going to be a switched DC signal. but mathematically, the amount of heat transfer the woofer will need to dissipate is going to be exactly the same whether you are sending 50% duty cycle 2x VDC or +/- x VDC to the woofer. The point is, at clipping, "rms" power dissipation calculations no longer apply, since "rms" is higher for clipped signals vs unclipped signals.


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## ChrisB

SQ_Bronco said:


> I'm confused- how do you "verify clipping" if you don't see the waveform change? If the waveform changes, there is a DC component of the signal.
> 
> The issue may be that the velleman is looking for a constant DC signal, whereas it's going to be a switched DC signal. but mathematically, the amount of heat transfer the woofer will need to dissipate is going to be exactly the same whether you are sending 50% duty cycle 2x VDC or +/- x VDC to the woofer. The point is, at clipping, "rms" power dissipation calculations no longer apply, since "rms" is higher for clipped signals vs unclipped signals.


So why doesn't my Fluke 117 measure DC voltage on the amplifier's outputs as the wave squares off?


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## sonikaccord

SQ_Bronco said:


> The distance a cone moves is based on the p-p voltage it sees. For a given peak-to-peak voltage, a clipped signal has twice as much electrical energy as a pure sine wave, but the woofer cone will move the same distance (function of p-p voltage) whether it is getting a sine wave or a square wave. Also note, the amount of heat produced by electrical resistance increases with the square of current (joule's 1st law, Q = I^2 * R), so doubling current creates (at least *) 4x the heat dissipation requirement.
> 
> (change temp of the conductor also increases resistance, so it's probably more than 4x).
> 
> The primary means to cool woofer coils is air forced across the voice coil by the cone motion. More energy with the same amount of cooling can easily lead to failure. This is clearly not a myth.
> 
> Anyway, a square wave is identical to a switched DC signal. ITRW, a clipped signal will probably not really be a square wave, since that would sound like aural sandpaper, but it should be easily visible on an oscilloscope.
> 
> ChrisB, can you please describe your test setup?


I was referring to a pure DC signal at first. But I agree. A square wave has more "area under the curve" than a sine wave which means it has more power than a sine wave. And as you said, power=heat which leads to blown VC's. 

Add the fact that inductors are shorted with DC sources and you basically turn your speaker into a resistor connected across the amp terminals at DC.

OSN put it the best. You can still have an AC signal above the x-axis, but would it be AC or DC?


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## alm001

ChrisB said:


> So why doesn't my Fluke 117 measure DC voltage on the amplifier's outputs as the wave squares off?


Because half the time the voltage is negative. 68hz is pretty fast. If you had an analog meter, it would be hard to see as well (if the needle could even keep up).
Are you really surprised you didn't find DC (as it is universally understood)?
If you want to measure the voltage peaks of the wave use a scope.


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## alm001

I am not trying to defend the DC argument. An oscillating square wave is not DC.
This is just a matter of ignorance.


But it _is_ (almost) *constant current*


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## ChrisB

alm001 said:


> Are you really surprised you didn't find DC (as it is universally understood)?


Nope. I only performed the test to put an electrical engineering student in his place on another forum. He was quoting book theory but had no idea of how things measure in the real world. Watching him try to explain my results was comical at best.:laugh:


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## DBfan187

good read on this subject

Clipping: damage from power or cone movement - CARSOUND.COM Forum


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## sqshoestring

Someone record me a sound that looks like a square wave, where it is flat at some voltage that is not zero.

IMO DC is a flat line not at zero, if you turn the knob on the scope you will see it. Its just a matter of time (division). Call it AC it does not really matter it is power either way, and it will blow the speaker faster. It is also not an electrical signal any natural sound would make, and the speaker does not make sound with static voltage. Its really a major screw up due to amp design that is not limited to its capacity. I still don't know why with all our technology hardly anyone can make an amp that does not clip or even soft clips like a tube, I guess they are too busy making toasters or something. Pro sound can make something clip any way you want, has for decades. Another one of those things that makes me wonder what year I'm living in.


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## finkster

sonikaccord said:


> But with DC the coil is also stationary and not cooling itself like it would with AC.


i highly doubt the motor has the strength to stay stationary for any period of time when it is still moving more than 30 times in most cases.

Think about a power to movement ratio.


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## ChrisB

sqshoestring said:


> Someone record me a sound that looks like a square wave, where it is flat at some voltage that is not zero.
> 
> IMO DC is a flat line not at zero, if you turn the knob on the scope you will see it. Its just a matter of time (division). Call it AC it does not really matter it is power either way, and it will blow the speaker faster. It is also not an electrical signal any natural sound would make, and the speaker does not make sound with static voltage. Its really a major screw up due to amp design that is not limited to its capacity. I still don't know why with all our technology hardly anyone can make an amp that does not clip or even soft clips like a tube, I guess they are too busy making toasters or something. Pro sound can make something clip any way you want, has for decades. Another one of those things that makes me wonder what year I'm living in.


I remember the DDT lights on my Peavey CS amplifiers when I used to DJ. If you want to talk about an amp that sounds like ass without equalization yet is rock solid rugged, those were the ones.

A little flicker of yellow from the DDT circuit wasn't a bad thing, but if you let it stay lit up in yellow too long, the next color was red because you were in thermal shutdown.  

Oh, and NEVER, under any circumstances, let your business partner see you bring one of the amps out of thermal with a CO2 canister blowing air through the amp. I thought I would never hear the end of his complaining the first time he saw me do that to "our" equipment.:laugh:


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## sonikaccord

finkster said:


> i highly doubt the motor has the strength to stay stationary for any period of time when it is still moving more than 30 times in most cases.
> 
> Think about a power to movement ratio.


Huh? It will be stationary for an infinite amount of time if DC is applied to the coil.
EDIT:as long as the dc is being applied an the coil doesn't burn up

In the case of clipping, the speaker attempts to play the n amount of harmonics that are created during clipping. No it wont't stay in the 'exact' same spot but the movement will be so small that you might as well say it is.

Power to movement ratio? You mean like voltage applied= x amount of excursion?


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## sqshoestring

ChrisB said:


> Oh, and NEVER, under any circumstances, let your business partner see you bring one of the amps out of thermal with a CO2 canister blowing air through the amp. I thought I would never hear the end of his complaining the first time he saw me do that to "our" equipment.:laugh:


LOL! Good one:laugh:



sonikaccord said:


> In the case of clipping, the speaker attempts to play the n amount of harmonics that are created during clipping. No it wont't stay in the 'exact' same spot but the movement will be so small that you might as well say it is.


I don't know exactly what way you mean this, but far as playing music I thought I read someone tested this and found the cone movement (xmax) was nearly the same with massive amounts of distortion, to the point of the music hardly being recognizable. Same with a square wave. However that does not discount the fact that more energy is contained in a square or clipped wave, so while the cooling may be the same/similar power is still increased. In my non-scientific experience clipping might cause a little more xmax, if there is more left.


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## ChrisB

sqshoestring said:


> LOL! Good one:laugh:



Of course you did bring up an interesting point. Why can't modern day 12v amplifiers utilize something like the Peavey DDT circuit? Aside from potential licensing costs to Peavey, you can't tell me it is that hard to implement a soft limiter that automagically reduces gain when it detects clipping on the output side.


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## sqshoestring

ChrisB said:


> Of course you did bring up an interesting point. Why can't modern day 12v amplifiers utilize something like the Peavey DDT circuit? Aside from potential licensing costs to Peavey, you can't tell me it is that hard to implement a soft limiter that automagically reduces gain when it detects clipping on the output side.


Like China needs permission...lol Yes I agree 100%, they put clipping lights on amps decades ago so what is up with this? The only one I know of is McIntosh. Everything else has auto levels built into it, why is this so difficult? Can something so stupid/old/simple actually still be patented? Why didn't someone patent headlights on cars.... Nothing against Peavey of course I'm talking car amps.


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## ChrisB

sqshoestring said:


> Like China needs permission...lol Yes I agree 100%, they put clipping lights on amps decades ago so what is up with this? The only one I know of is McIntosh. Everything else has auto levels built into it, why is this so difficult? Can something so stupid/old/simple actually still be patented? Why didn't someone patent headlights on cars.... Nothing against Peavey of course I'm talking car amps.


Attached is the old patent for the circuit!


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## sonikaccord

sqshoestring said:


> LOL! Good one:laugh:
> 
> 
> I don't know exactly what way you mean this, but far as playing music I thought I read someone tested this and found the cone movement (xmax) was nearly the same with massive amounts of distortion, to the point of the music hardly being recognizable. Same with a square wave. However that does not discount the fact that more energy is contained in a square or clipped wave, so while the cooling may be the same/similar power is still increased. In my non-scientific experience clipping might cause a little more xmax, if there is more left.


Max cone movement is based on voltage. We know this.
It will move the same distance whether it's a sine wave or a square wave and long as the peak voltage is the same.
The difference in a sine wave and a square wave is of course the area under the curve. The square wave causes the cone to become stationary on the peaks for a short amount of time, but it also receives that peak voltage for an extended amount of time.
When music is clipped, it doesn't produce a perfect plateau. There are little ripples on the signals that the speaker tries to play. That's what I was saying about the 'n' harmonics and those ripples are the distortion.


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## mda185

For all of you saying that clipped, square waves have more area under the curve and thus, more power delivered to the speaker, you are right. This is what burns the voice coil out. There is another aspect of clipped waves that is particularly damaging to midranges and tweeters. The square wave has a lot more energy at high frequencies than a sine wave. (Think of all the harmonics of the fundamental frequency.) This energy gets through the crossover filter and causes more damage to the high frequency drivers. 

So the old saying about DC voltage in a clipped signal is wrong. It is just more energy getting to the voice coils with a duty cycle that approaches 100%. The positive and negative voltage peaks are at or near the max voltages of the power supply rails and Duty cycle approaches 100% because the voice coil has either positive or negative voltage on it almost all the time with a symmetrical square wave. That means that there is little or no cool down time for the voice coils under these conditions, glue melts, and the voice coil becomes liberated from the former.


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## the_gooch

Theoretically if you define the period to be < or = to the length of time the signal is clipped then it would be DC as there is no dV/dT.


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## sonikaccord

the_gooch said:


> Theoretically if you define the period to be < or = to the length of time the signal is clipped then it would be DC as there is no dV/dT.


In that case, theoretically, 0 to pi is positive dc and 0 to -pi is negative dc just with a very large ripple. As long as it doesn't cross the x-axis (change direction) it's dc...

Edit: That's with a sine wave, not cosine.


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## Chaos

mda185 said:


> For all of you saying that clipped, square waves have more area under the curve and thus, more power delivered to the speaker, you are right. This is what burns the voice coil out. There is another aspect of clipped waves that is particularly damaging to midranges and tweeters. The square wave has a lot more energy at high frequencies than a sine wave. (Think of all the harmonics of the fundamental frequency.) This energy gets through the crossover filter and causes more damage to the high frequency drivers.
> 
> So the old saying about DC voltage in a clipped signal is wrong. It is just more energy getting to the voice coils with a duty cycle that approaches 100%. The positive and negative voltage peaks are at or near the max voltages of the power supply rails and Duty cycle approaches 100% because the voice coil has either positive or negative voltage on it almost all the time with a symmetrical square wave. That means that there is little or no cool down time for the voice coils under these conditions, glue melts, and the voice coil becomes liberated from the former.



Quoted as truth.



As for _why_ the vast majority of mobile audio amps don't have clipping indicators, let alone a circuit to minimize it - if they were foolproof, there wouldn't be nearly as many consumers in the market for new amplifiers each quarter, now would there?


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## the_gooch

sonikaccord said:


> In that case, theoretically, 0 to pi is positive dc and 0 to -pi is negative dc just with a very large ripple. As long as it doesn't cross the x-axis (change direction) it's dc...
> 
> Edit: That's with a sine wave, not cosine.



Actually, you are correct. Take a rectified SIN wave, it is regarded as DC since there is no change in polarity. DC with a rather large ripple that would require capacitance to smooth that ripple to a usable range.


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## bose301s

SQ_Bronco said:


> The distance a cone moves is based on the p-p voltage it sees. For a given peak-to-peak voltage, a clipped signal has twice as much electrical energy as a pure sine wave, but the woofer cone will move the same distance (function of p-p voltage) whether it is getting a sine wave or a square wave. Also note, the amount of heat produced by electrical resistance increases with the square of current (joule's 1st law, Q = I^2 * R), so doubling current creates (at least *) 4x the heat dissipation requirement.
> 
> (change temp of the conductor also increases resistance, so it's probably more than 4x).
> 
> The primary means to cool woofer coils is air forced across the voice coil by the cone motion. More energy with the same amount of cooling can easily lead to failure. This is clearly not a myth.
> 
> Anyway, a square wave is identical to a switched DC signal. ITRW, a clipped signal will probably not really be a square wave, since that would sound like aural sandpaper, but it should be easily visible on an oscilloscope.
> 
> ChrisB, can you please describe your test setup?


However with more resistance comes less current as well creating basically a feedback loop that controls current and resistance to a certain point.


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## dstaley

Guys, keep in mind that car amplifiers don't ever change polarity- there is no H-bridge driver, the + lead never drives negative to draw the woofer back into the suspension. The amps drive with DC, and the output is DC. The signal has an AC component, but with a DC bias equal to half of the amplitude.

The reason that clipping is more damaging to the voice coils is that when there is no change in voltage (clipping) the inductive properties of the coil do not act as part of the circuit, so all you have is a wire that starts to look more like a short circuit (wire resistance rather than impedance). When the signal changes with time (dV/dt for calculus minded engineers and mathematicians) the inductance of the woofer (reactance) changes the waveform and reduces the heat dissipated because the power is converted to work (moving air) rather than converting 100% of the power to heat (stationary cone).


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## 14642

It's NOT DC

This is all pretty simple if you just consider power. Power isn't determined by signal polarity. There's just as much power in +100V applied to a 4 ohm load as -100V applied to the same load, since power is the square of the voltage divided by the resistance of the load. 

The best measure to use to understand this is "continuous average". For a sine wave, continuous average is .707 x the square of the peak voltage divided by the load's resistance. For a square wave, continuous average is 1 x the square of the peak voltage dvided by the load's resistance. so if your amp makes 10V and it's connected to a 4-ohm resistor, a sine wave would produce (.707 x 10^2) / 4 or 17.6 watts, continuous average. The same amplifier playing a square wave would produce (1 x 10^2)/4 or 25 watts, continuous average.

As the previous poster indicated, if the speaker is moving, some power is converted into motion and some into heat. If the speaker isn't moving, all the power is converted into heat. The amount of time that the speaker is moving when it's playing a square wave is reduced compared to playing a sine wave. The inductor creates motion and only "operates" on changing voltage and current, so it's only effective when the voltage is moving from high to low and from low to high. It doesn't do anything while the signal is high OR low. 

Therefore, during MOST of the time that the output of the amp is constantly high or low (against the voltage rail) when the signal is clipped, the power is converted into heat. The time constant of the inductor and the voice coil's DCR cause the speaker to move more slowly than the signal when the voltage changes polarity instantly in a clipped signal. That's a low pass filter. 

So, a more inductive speaker (subwoofer) is more likely to withstand square wave than a less inductive speaker (tweeter) for the reason above and also because a woofer is likely to have a bigger, beefier coil.


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## envisionelec

dstaley said:


> Guys, keep in mind that car amplifiers don't ever change polarity- there is no H-bridge driver, the + lead never drives negative to draw the woofer back into the suspension. The amps drive with DC, and the output is DC. The signal has an AC component, but with a DC bias equal to half of the amplitude.


Wrong. How do you come to such a conclusion??



dstaley said:


> The reason that clipping is more damaging to the voice coils is that when there is no change in voltage (clipping) the inductive properties of the coil do not act as part of the circuit, so all you have is a wire that starts to look more like a short circuit (wire resistance rather than impedance). When the signal changes with time (dV/dt for calculus minded engineers and mathematicians) the inductance of the woofer (reactance) changes the waveform and reduces the heat dissipated because the power is converted to work (moving air) rather than converting 100% of the power to heat (stationary cone).


Wrong. Inductance has nothing to do with it. It's all about average vs. maximum power. Not DC. Not inductance. 



Andy Wehmeyer said:


> It's NOT DC
> 
> This is all pretty simple if you just consider power. Power isn't determined by signal polarity. There's just as much power in +100V applied to a 4 ohm load as -100V applied to the same load, since power is the square of the voltage divided by the resistance of the load.
> 
> The best measure to use to understand this is "continuous average". For a sine wave, continuous average is .707 x the square of the peak voltage divided by the load's resistance. For a square wave, continuous average is 1 x the square of the peak voltage dvided by the load's resistance. so if your amp makes 10V and it's connected to a 4-ohm resistor, a sine wave would produce (.707 x 10^2) / 4 or 17.6 watts, continuous average. The same amplifier playing a square wave would produce (1 x 10^2)/4 or 25 watts, continuous average.
> 
> As the previous poster indicated, if the speaker is moving, some power is converted into motion and some into heat. If the speaker isn't moving, all the power is converted into heat. The amount of time that the speaker is moving when it's playing a square wave is reduced compared to playing a sine wave. The inductor creates motion and only "operates" on changing voltage and current, so it's only effective when the voltage is moving from high to low and from low to high. It doesn't do anything while the signal is high OR low.
> 
> Therefore, during MOST of the time that the output of the amp is constantly high or low (against the voltage rail) when the signal is clipped, the power is converted into heat. The time constant of the inductor and the voice coil's DCR cause the speaker to move more slowly than the signal when the voltage changes polarity instantly in a clipped signal. That's a low pass filter.
> 
> So, a more inductive speaker (subwoofer) is more likely to withstand square wave than a less inductive speaker (tweeter) for the reason above and also because a woofer is likely to have a bigger, beefier coil.


Yes...then NO. 

Inductance has nothing to do with it. A tweeter has nowhere near the voice coil dissipation ability of a woofer. The shift in power distribution through power compression puts the tweeter in danger because a significantly larger percentage of overall power is being delivered to the tweeter during clipping. More clipping, more power.

DC output doesn't happen unless an output device shorts, but extreme clipping can result from a marginally designed amplifier in a phenomenon called "rail sticking".


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## dstaley

envisionelec said:


> Wrong. How do you come to such a conclusion??
> 
> 
> 
> Wrong. Inductance has nothing to do with it. It's all about average vs. maximum power. Not DC. Not inductance.
> 
> 
> 
> Yes...then NO.
> 
> Inductance has nothing to do with it. A tweeter has nowhere near the voice coil dissipation ability of a woofer. The shift in power distribution through power compression puts the tweeter in danger because a significantly larger percentage of overall power is being delivered to the tweeter during clipping. More clipping, more power.
> 
> DC output doesn't happen unless an output device shorts, but extreme clipping can result from a marginally designed amplifier in a phenomenon called "rail sticking".



I come up with that conclusion because I understand the math, the amplifier schematics, and the system interaction between the power supply, the output drivers, and the motor. Try looking at the signal with a current probe and you will note that the current flows in only one direction. When the amplifier drives the voice coil, it has only one polarity to drive with. It charges the voice coil, which is a wire looped multiple times to form an armature. The inductance of this armature is defined by the equation:










When installed in the speaker, this loop of wire has a higher effective inductance because the materials the voice coil are made of enhance the magnetic strength (as well as provide an opposing static counteracting magnetic flux, resulting in a net force). You can read more about this by reading the Wikipedia article on inductance.

Automotive amplifiers have a positive (+) and a negative (-) power supply. In class AB amplifier the supply is independent but load sensing, and in a class D amplifier the output drivers and the power supply are integrated. See the block diagram from the Wikipedia article on Class D amplifiers:










By definition, saturation is when the output reaches the maximum available amplitude, resulting in a nonlinear flat output. When the output is a flat, constant voltage, by definition the output is direct current. Connect an oscilloscope to the output and you will see the flat portions of the signal when it clips- during these periods you will see periods of DC output. In an AB amplifier the output drivers are switched full ON during this period- acting as a short. In a class D amplifier, the output drivers are running at 100% output capacity. In a class D amplifier, a short circuit is not necessarily the worst case condition for the voice coil.


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## envisionelec

dstaley said:


> I come up with that conclusion because I understand the math, the amplifier schematics, and the system interaction between the power supply, the output drivers, and the motor. Try looking at the signal with a current probe and you will note that the current flows in only one direction. When the amplifier drives the voice coil, it has only one polarity to drive with. It charges the voice coil, which is a wire looped multiple times to form an armature. The inductance of this armature is defined by the equation:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> When installed in the speaker, this loop of wire has a higher effective inductance because the materials the voice coil are made of enhance the magnetic strength (as well as provide an opposing static counteracting magnetic flux, resulting in a net force). You can read more about this by reading the Wikipedia article on inductance.
> 
> Automotive amplifiers have a positive (+) and a negative (-) power supply. In class AB amplifier the supply is independent but load sensing, and in a class D amplifier the output drivers and the power supply are integrated. See the block diagram from the Wikipedia article on Class D amplifiers:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> By definition, saturation is when the output reaches the maximum available amplitude, resulting in a nonlinear flat output. When the output is a flat, constant voltage, by definition the output is direct current. Connect an oscilloscope to the output and you will see the flat portions of the signal when it clips- during these periods you will see periods of DC output. In an AB amplifier the output drivers are switched full ON during this period- acting as a short. In a class D amplifier, the output drivers are running at 100% output capacity. In a class D amplifier, a short circuit is not necessarily the worst case condition for the voice coil.


You slay me. :laugh:

Go build a few car amplifiers. No - wait - go build AN AMPLIFIER and tell me you're still right.

Please, back away from the books. They're not helping your cause. I'd love to give you more explanation, but I have other things to do.


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## Hispls

ChrisB said:


> So where is this evidence of DC produced during clipping?
> 
> One of my friends had an Elemental Designs amplifier blow and send direct DC to his subs therefore taking them out. Aside from serious malfunction, I have yet to measure any significant DC voltage delivered by an amplifier to the speaker outputs at clipping.



Take a heavily clipped sine wave and make a simple voltage regulator with 4 diodes and you'll get solid dc.

This "myth" isn't the whole truth, but is on the right track IMO.


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## dstaley

envisionelec said:


> You slay me. :laugh:
> 
> Go build a few car amplifiers. No - wait - go build AN AMPLIFIER and tell me you're still right.
> 
> Please, back away from the books. They're not helping your cause. I'd love to give you more explanation, but I have other things to do.


I have. Check with your engineering staff, they will help you understand.


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## envisionelec

dstaley said:


> I have. Check with your engineering staff, they will help you understand.


I AM the engineering staff.


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## sqshoestring

Lols. The problem is that amplifier engineers/designers don't give a crap what happens when the amp clips. Its outside the ratings and capacity of the amplifier. Personally I'd like an amp that soft clips and/or limits, but I don't see very many. It protects my hearing and allows a smaller amp to be used if I can run it to its limits, which you can't with an amp that clips like broken glass because it sounds so bad.


----------



## sonikaccord

So how hard is it to make an automatic gain control? and still be reliable? That would solve half of the problem.


----------



## 14642

Hispls said:


> Take a heavily clipped sine wave and make a simple voltage regulator with 4 diodes and you'll get solid dc.
> 
> This "myth" isn't the whole truth, but is on the right track IMO.


Why does this matter? Of course, rectifying AC will produce DC. That doesn't mean that AC is DC. A square wave is NOT DC. IF it was DC, then there would be no way to filter the high frequency components from the signal. With a square wave, that filter is a simple inductor.

Furthermore, it's unfair and unreasonable to assume or assert that amplifier designers don't care what happens when an amp clips. The gain limiter is one approach, but it has its drawbacks too. There's nothing wrong with a little clipping--in fact, we don't hear it on transients very well. If you want to eliminate it completely, just set your input sensitivity control with a sine wave track recorded at 0dB and an O-scope.

You'll hate it.


----------



## Hispls

Andy Wehmeyer said:


> Why does this matter? Of course, rectifying AC will produce DC. That doesn't mean that AC is DC. A square wave is NOT DC. IF it was DC, then there would be no way to filter the high frequency components from the signal. With a square wave, that filter is a simple inductor.
> 
> Furthermore, it's unfair and unreasonable to assume or assert that amplifier designers don't care what happens when an amp clips. The gain limiter is one approach, but it has its drawbacks too. There's nothing wrong with a little clipping--in fact, we don't hear it on transients very well. If you want to eliminate it completely, just set your input sensitivity control with a sine wave track recorded at 0dB and an O-scope.
> 
> You'll hate it.


The point is the more clipped it is the less ripple you would have with that simple rectifier.

A true sine wave is 70.7% the power of DC voltage of the same peak when averaged over time. I would hazzard to guess that a heavily clipped sine wave is closer to 100%. An extra effective 30% power will push a lot of systems over the edge. So in practice a heavily clipped 700W RMS sine wave is the equivelant of running 1000W DC power through the same system. So while it is actually an alternating current, in practice it might as well be DC with a value of the peak of your sine waves.

Again not true as stated, but in practice it's a fair explanation for what's going on. The people who argue this already understand what's going on and are just trolling, people who don't understand will accept it and hopefully not run their equipment into abusive conditions.


----------



## sqshoestring

Andy Wehmeyer said:


> Furthermore, it's unfair and unreasonable to assume or assert that amplifier designers don't care what happens when an amp clips. The gain limiter is one approach, but it has its drawbacks too. There's nothing wrong with a little clipping--in fact, we don't hear it on transients very well. If you want to eliminate it completely, just set your input sensitivity control with a sine wave track recorded at 0dB and an O-scope.
> 
> You'll hate it.


Sorry Andy I do not mean that in a negative way towards amp designers though it kind of sounded that way, it just appears that clipping is not really addressed....and designers build what they are told to; if its not rated for that use then why would a company bother having a designer worry much about it? Maybe I assumed too much. I think a MacIntosh is the only one I have seen with some limiting on it. Limiting may not be that great I never had one, what is useful is tube-like clipping because then you know it is clipping and can back it off yet it is not offensive. 

I have some favorite amps that (sound-wise) always clip in the bass first, they actually play louder with a high pass. This could be a weak power supply they are pre-mosfet amps, I don't know not have time to try to test and find out with my limited equipment. I don't know what aspects of amp design affect the clipping response/harmonics and do realize you have limited options because you are beyond the capacity of the amplifier. Also if you soft clip you are actually modifying the original signal, but hey IMHO if you are going to run it there then you choose something and I am ok with that. Maybe it is difficult to do, or more amps would have a switch on the side to select soft clipping or limiting/etc., they have every other feature they can think of. I've never really seen an answer to this question. I have seen patents posted for non-car audio equipment of circuits used to do this so maybe it is a patent issue. It could be a marketing issue as well.

Yes I always have excessive gain in my system because source material varies so much, but I never abuse my equipment so its not a problem. I don't often use that much power anyway, this new infinty kappa 4 is large as I ever run on highs and it seems to have some muscle. I have not really pushed it that hard because it goes loud on my scale. I don't think clipping will be a big issue with it for my use. Also worth noting that older Infinity amps are one of the few I have seen clipping lights on.


----------



## envisionelec

sqshoestring said:


> Lols. The problem is that amplifier engineers/designers don't give a crap what happens when the amp clips. Its outside the ratings and capacity of the amplifier. Personally I'd like an amp that soft clips and/or limits, but I don't see very many. It protects my hearing and allows a smaller amp to be used if I can run it to its limits, which you can't with an amp that clips like broken glass because it sounds so bad.


Oooh, that hurts. Of COURSE we care what happens at clipping. An amplifier should be stable during all operating modes, including clipping. That's not to say that all actually are. Some amplifiers, especially early solid state types, have such a shallow phase margin that they break into oscillation at clipping. This blows tweeters very quickly. It can also damage the amplifier itself if the oscillation is prolonged or especially severe.


----------



## envisionelec

Hispls said:


> The point is the more clipped it is the less ripple you would have with that simple rectifier.
> 
> A true sine wave is 70.7% the power of DC voltage of the same peak when averaged over time. I would hazzard to guess that a heavily clipped sine wave is closer to 100%. An extra effective 30% power will push a lot of systems over the edge. So in practice a heavily clipped 700W RMS sine wave is the equivelant of running 1000W DC power through the same system. So while it is actually an alternating current, in practice it might as well be DC with a value of the peak of your sine waves.
> 
> Again not true as stated, but in practice it's a fair explanation for what's going on. The people who argue this already understand what's going on and are just trolling, people who don't understand will accept it and hopefully not run their equipment into abusive conditions.


Thanks for using science and application to prove a point. I tried, but the board was down so much this week I gave up trying to post. 

Anyway, I took pictures of what the peak voltage is during a sine wave vs square wave. I could post them if necessary, but I don't feel it IS necessary.  The results mirror reality (go figure): DC levels were - TADA! *ZERO!* The only way you could achieve any DC level is if there is asymmetry in the signal. If your amplifier's output becomes asymmetrical at clipping, it is a piece of sh*t, hands down. I didn't even think to enter this into the equation because it's such a travesty of engineering if this actually happens...

HiSPLs is right. No need to repeat what he said...


----------



## envisionelec

sqshoestring said:


> Sorry Andy I do not mean that in a negative way towards amp designers though it kind of sounded that way, it just appears that clipping is not really addressed....and designers build what they are told to; if its not rated for that use then why would a company bother having a designer worry much about it? Maybe I assumed too much. I think a MacIntosh is the only one I have seen with some limiting on it. Limiting may not be that great I never had one, what is useful is tube-like clipping because then you know it is clipping and can back it off yet it is not offensive.


McIntosh uses PowerGuard. It works, it is musical (it doesn't interfere too much with the natural dynamics of recorded music) and it is (was) patented. But they're not the only manufacturer using compression - but maybe the only ones in the car audio market. It is strange though, because the automotive environment is an IDEAL place for using compression. Unless you're listening in the driveway with the key off...



sqshoestring said:


> I have some favorite amps that (sound-wise) always clip in the bass first, they actually play louder with a high pass. This could be a weak power supply they are pre-mosfet amps, I don't know not have time to try to test and find out with my limited equipment. I don't know what aspects of amp design affect the clipping response/harmonics and do realize you have limited options because you are beyond the capacity of the amplifier. Also if you soft clip you are actually modifying the original signal, but hey IMHO if you are going to run it there then you choose something and I am ok with that. Maybe it is difficult to do, or more amps would have a switch on the side to select soft clipping or limiting/etc., they have every other feature they can think of. I've never really seen an answer to this question. I have seen patents posted for non-car audio equipment of circuits used to do this so maybe it is a patent issue. It could be a marketing issue as well.


I doubt they clip "in the bass" first, but it's where you first notice it due to the spectral power density in pop music. MosFET vs Biploar has nothing to do with a power supply's ability to *deliver* current. It's an efficiency thing. MosFETs are actually not as fast as BiPolar, but they are more efficient. You'd have to be a designer to understand why this is important to the application. But I digress.

Some amplifiers clip "early" because they have insufficient output drive current one or two stages upstream from the final outputs. Some output devices have pretty terrible Hfe (gain) at high current. To compensate, the feedback circuit has to work really hard to keep up, shoving more current into the drivers to keep the voltage gain up. Well, this isn't done that well in some of the old school amps. Sometimes it was because the designs outpaced technology for driving low impedance loads. Other times, the designer didn't really understand the application. This is also why some amplifiers sound "better" when not driving 2 ohm or highly reactive loads. Everything's 20/20 in retrospect. 



sqshoestring said:


> Yes I always have excessive gain in my system because source material varies so much, but I never abuse my equipment so its not a problem. I don't often use that much power anyway, this new infinty kappa 4 is large as I ever run on highs and it seems to have some muscle. I have not really pushed it that hard because it goes loud on my scale. I don't think clipping will be a big issue with it for my use. Also worth noting that older Infinity amps are one of the few I have seen clipping lights on.


There used to be a lot more of them. But to be honest, people hate them because "it's not loud enough" or "I don't hear any distortion" is a common complaint when the installer would set gains. It's a psychological thing. A flashing red light typically indicates "overload" or "danger" and people tend to view those amplifiers as weaker than another brand _without a clipping indicator._


----------



## envisionelec

sonikaccord said:


> So how hard is it to make an automatic gain control? and still be reliable? That would solve half of the problem.


Reliable or musical? Reliability is easy, making it sound good is another thing all together.


----------



## sqshoestring

envisionelec said:


> Oooh, that hurts. Of COURSE we care what happens at clipping. An amplifier should be stable during all operating modes, including clipping. That's not to say that all actually are. Some amplifiers, especially early solid state types, have such a shallow phase margin that they break into oscillation at clipping. This blows tweeters very quickly. It can also damage the amplifier itself if the oscillation is prolonged or especially severe.


Yeah I was a little course, sorry, I know you guys try or you would not be on a board at the least. My bad.:blush:



envisionelec said:


> McIntosh uses PowerGuard. It works, it is musical (it doesn't interfere too much with the natural dynamics of recorded music) and it is (was) patented. But they're not the only manufacturer using compression - but maybe the only ones in the car audio market. It is strange though, because the automotive environment is an IDEAL place for using compression. Unless you're listening in the driveway with the key off...


That is what I should have said.


envisionelec said:


> I doubt they clip "in the bass" first, but it's where you first notice it due to the spectral power density in pop music. MosFET vs Biploar has nothing to do with a power supply's ability to *deliver* current. It's an efficiency thing. MosFETs are actually not as fast as BiPolar, but they are more efficient. You'd have to be a designer to understand why this is important to the application. But I digress.
> 
> Some amplifiers clip "early" because they have insufficient output drive current one or two stages upstream from the final outputs. Some output devices have pretty terrible Hfe (gain) at high current. To compensate, the feedback circuit has to work really hard to keep up, shoving more current into the drivers to keep the voltage gain up. Well, this isn't done that well in some of the old school amps. Sometimes it was because the designs outpaced technology for driving low impedance loads. Other times, the designer didn't really understand the application. This is also why some amplifiers sound "better" when not driving 2 ohm or highly reactive loads. Everything's 20/20 in retrospect.


PS design is a difficult one to understand lol, I've been working on it. I know mosfets are faster and have less switching losses, and tend to handle more power for a given size. The gate and base work a little differently.

One of the amps is a alpine 3518 its only 2x35 or so, since they are DIN only you can find them cheap as dirt if you are curious. I know what you hear is not necessarily what the electrons are doing, but it is very weak at making bass and sounds good making about 150Hz and up. I never noticed any difference at 2 or 4 ohm loads, but only used it on a high pass. 2 ohms is not listed in the manual and it needs a fan on 4 ohms lol, so I always used a fan. One of these amps I clipped on a scope and it seems to make a peak then the backside is deformed, like it emptied the rail caps and dropped at the peak...at the verge of clipping. Most SS amps will more or less show a flat at the peak. But I do not know exactly what it is doing to make that deformation at the peak, and assume that is what makes the clipping sound different....and am sure there is a lot more to it than that.

Far as power maybe it is just because bass requires more apparent power in a car? There is a difference however, I took that amp out and put in a kicker and much unlike the alpine I could change the high pass and it would clip at the same volume on the HU. The alpine would clip sooner the lower the low pass was.


envisionelec said:


> There used to be a lot more of them. But to be honest, people hate them because "it's not loud enough" or "I don't hear any distortion" is a common complaint when the installer would set gains. It's a psychological thing. A flashing red light typically indicates "overload" or "danger" and people tend to view those amplifiers as weaker than another brand _without a clipping indicator._


Ha, yes very good marketing point! I know from testing some amps that they clip far before you know it in particular in the bass regions. I have one of those huge infinity 4x111rms but not tried it yet, the class D is amazingly smaller but I can fit either. Nobody talks about Infinity amps it seems.


----------



## sonikaccord

envisionelec said:


> Reliable or musical? Reliability is easy, making it sound good is another thing all together.


Why not both? Maybe something that can back down on the gain when it senses the input voltage approaching a predetermined setting? It would be cool to implement but it does sound (pun) like too much would be in the signal path.


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## envisionelec

sqshoestring said:


> Yeah I was a little course, sorry, I know you guys try or you would not be on a board at the least. My bad.:blush:
> 
> 
> That is what I should have said.
> 
> PS design is a difficult one to understand lol, I've been working on it. I know mosfets are faster and have less switching losses, and tend to handle more power for a given size. The gate and base work a little differently.
> 
> One of the amps is a alpine 3518 its only 2x35 or so, since they are DIN only you can find them cheap as dirt if you are curious. I know what you hear is not necessarily what the electrons are doing, but it is very weak at making bass and sounds good making about 150Hz and up. I never noticed any difference at 2 or 4 ohm loads, but only used it on a high pass. 2 ohms is not listed in the manual and it needs a fan on 4 ohms lol, so I always used a fan. One of these amps I clipped on a scope and it seems to make a peak then the backside is deformed, like it emptied the rail caps and dropped at the peak...at the verge of clipping. Most SS amps will more or less show a flat at the peak. But I do not know exactly what it is doing to make that deformation at the peak, and assume that is what makes the clipping sound different....and am sure there is a lot more to it than that.
> 
> Far as power maybe it is just because bass requires more apparent power in a car? There is a difference however, I took that amp out and put in a kicker and much unlike the alpine I could change the high pass and it would clip at the same volume on the HU. The alpine would clip sooner the lower the low pass was.
> 
> Ha, yes very good marketing point! I know from testing some amps that they clip far before you know it in particular in the bass regions. I have one of those huge infinity 4x111rms but not tried it yet, the class D is amazingly smaller but I can fit either. Nobody talks about Infinity amps it seems.


I think you misread what I posted about the speed of MosFETs vs bipolars. They're not as fast due to gate charge injection current. For general car amplifier power supply use, the benefits of MosFETs outweigh the bipolar by a significant margin. But it's also the reason that good, high-power, full range Class D amplifiers are hard to find.

I know the Alpine amps very well, especially the DIN-only versions. It's really a hokey, standard-issue Japanese design - it uses an IC driver chip that isn't known for good clipping behavior and uses loads of global feedback. It's not really the power supply's fault, although the filter capacitors might need to be checked, but I doubt they're to blame. The 3527 is the same way, but in four channels. 

The 1980-1990's Japanese amplifiers are a great example of over-engineered but misunderstood design criteria. They'll use 16 transistors for the remote turn-on circuit, but they didn't have a great concept of how Americans listen to music. If you ever worked at a shop during that time period and the shop sold an American brand and a Japanese brand or brands, you would see that the American brands outsold the Japanese week after week. They were perceived as "weak" or "low powered" compared to their American brethren. It wasn't until they got the American marketing reps involved that Alpine came out with their V12 series, Kenwood the Excelon, Sony Mobile ES and so forth. They were designed to compete with American amps. Of course, at that time, American amps were taking a backseat as they folded and were bought out by Korean/Chinese interests. And then most car amps turned into what we have today - either massive Class D amps or cheap Class B (yup!), ever-shrinking Korean jobs that clip early and softly due to the problems aforementioned (a few posts up). That's a whole other issue.

Which is my last point = old school isn't always best, _especially_ when it comes to Japanese amps. Reminder - not ALL Alpine amps were like this, but certainly the entry level up to ~$400 amps were.


----------



## sqshoestring

I know the upc1225h are not considered to be anything special either, so I still don't know why they seemed appealing. I have one I have run on and off since the 80s. I'm about to give up on some of these old school amps they sit around and I don't run them or have no time to play with them, the ones I tried were not ideal for one reason or another. Gets to the point where I want something in the car that works.


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## rexroadj

hirxot said:


> yepp!


You have gone down the list of "new post" and just wrote "yepp!" on every one of them! STOP POST DUMPING TO BUILD POST COUNTS! MODS....Erase his BS!


----------



## XtremeRevolution

Here's a resource on clipping and voice coil damage that people might find very, very useful. 

CARSOUND.COM Forum - View Single Post - Clipping: damage from power or cone movement


----------



## djkomplex

I always wanted to know... say you send a 0db square wave test tone thru your amp... would this be the same as clipping? Also I see illustrations showing the peaks of the audio being flattened out... I know in a studio when I run a track thru a maximizing plugin it will create tracks that look liks this along the tops... just something I wondered. I am guessing its bad as when clipping, the amp is sending more power than it should versus playing a square wave where the amp is not clipping.


----------



## minbari

not reading all this.


but a fully clipped signal is exactly like sending it pulsed DC. the rise and fall times are insignificant to the time that it sits at full DC rails.


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## djkomplex

Yeah, I actually read that post by the guy from JL and saw.


----------



## TrickyRicky

ChrisB said:


> Of course you did bring up an interesting point. Why can't modern day 12v amplifiers utilize something like the Peavey DDT circuit? Aside from potential licensing costs to Peavey, you can't tell me it is that hard to implement a soft limiter that automagically reduces gain when it detects clipping on the output side.


Mtx mta from the late 80's/ early 90's have clipping indicators. Not hard to build on any amp. The question is will this prevent idiots(mosly teens and bass heads) from clipping the **** out of their signal?


----------



## alm001

TrickyRicky said:


> Mtx mta from the late 80's/ early 90's have clipping indicators. Not hard to build on any amp. The question is will this prevent idiots(mosly teens and bass heads) from clipping the **** out of their signal?


In college I had a set of MB quart PSC216's with the music comp crossovers.
(PPI PC4400 Bi-amped to them)
They had lights as tweeter protection. And before I knew that they were there to protect the tweeters I thought it was awesome that they would light up during the cymbal crashes on 'Sandstorm'.

That amp and speaker combo did sound incredible tho.


----------



## biggy238

I want to point out that although some of you that might not want to post information/pictures/proof of concept (for whatever reason), there are those of us novices that are soaking up and wading through the information you are providing.

My curiosity with this lies in the thought that an amplifier would have to be driven well beyond the initial point of clipping to create the kind of damage being discussed? I think one of you mentioned an additional 30% power increase of a clipped signal. 

Also, i'm curious about where I can find clarification on the topic of an audio amplifiers output being AC vs DC during it's operation. My layman comprehension of the circuits limit output to DC due to a lack in oscillation from the amplifier. Again, this is totally due to my assumption and nowhere near rooted in factuality. I've simply never looked into it before. Point me somewhere and I would love to read up. 

So far the thread drove me to read into sinusoidal output from dc to ac power inverters. Seemed like a good point to start to learn how high-low switching is accomplished. (DAC in audio?) 
Also explained how that cheapass walmart power inverter almost cost my uncles sawzall way back when I was in highschool.

Thanks, Kyle


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## junglejuice72

How does all of this theory account for a clipping lower powered amp burning out drivers where more power (3-4x more) played at a similar level caused no issues with the same model drivers, and this applied to tweeters and subs?????


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## ern2112

Power does not blow speakers..it never has and never will..heat does. When a sign wave is clipped, it causes the speaker to "hang" for a time at the top of the wave and at the bottom....and during that time its like putting a battery on the speaker terminals. Giving enough time and heat....the voice coil will blow.


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## MarkZ

ern2112 said:


> Power does not blow speakers..it never has and never will..heat does. When a sign wave is clipped, it causes the speaker to "hang" for a time at the top of the wave and at the bottom....and during that time its like putting a battery on the speaker terminals. Giving enough time and heat....the voice coil will blow.


Please read the thread _closely_.

Another thread that might clear things up is this one:

http://www.diymobileaudio.com/forum/general-car-audio-discussion/87065-underpowering-sub.html

which directly addresses the post you made.


----------



## ern2112

ChrisB said:


> I can't tell you how many times I heard that clipping will send DC voltage to your subs which will in turn ruin them rather quickly. I recently had 4 Orion HCCA 225 Digital reference amplifiers on my test bench and I measured DC voltage in the millivolt range at clipping with my Fluke 117. Furthermore, there is DC Voltage in the millivolt range at power levels below clipping.
> 
> What gives? Where is this DC voltage that will damage subwoofers quickly?



We have spent a little time on this subject too. I think one reason you cannot "see" the dc so well is because cancels itself out a bit due to the top and bottom of the sine wave being chopped...and a meter just cannot see it that well. I may be wrong though..... I will say that we ran a test with dc light bulbs to see how quickly they would light up compared to the O scope seeing some square waves.....and the scope shows clipping before the bulbs ever lit up. To expand on your point about Dc being present always...we used an amp with a lot more power to see what would happen...and the lights lit up before the amp ever came close to clipping.

This is an interesting subject and I do not know if "DC" is the right term....but I can tell you 100% of the amps we tested all had some dc present on the speakers leads...and when railing on the amp.....it lights the hell out of a DC light bulb way way before the amp ever square waves.


----------



## MarkZ

If you read that thread I linked to, you'll understand why that's not DC...


----------



## donnieL72

:dead_horse:

How's this for ya............

AC is just DC traveling back and forth in two different directions.......:laugh:


----------



## ern2112

MarkZ said:


> If you read that thread I linked to, you'll understand why that's not DC...


Yeah.....still not sure I am going to disagree or agree with this.....but I will say this Mark....you have good taste in cars. I have an 2006 Volvo S60R myself and love it! Looking for pics of your install.....figure I will stumble on them soon.


----------



## MarkZ

I love it. It's close to 200k miles right now and you wouldn't know it from driving it. Also a very good car for audio... good tweeter positioning (although I believe Andy W moved his about 9 inches), large center channel, large speaker openings w/ decent depth, and the trunk is very IB-amenable. 

I took down the install pics last year, but will post some at mobile sound science when I revamp my install the next couple months.


----------



## ern2112

MarkZ said:


> I love it. It's close to 200k miles right now and you wouldn't know it from driving it. Also a very good car for audio... good tweeter positioning (although I believe Andy W moved his about 9 inches), large center channel, large speaker openings w/ decent depth, and the trunk is very IB-amenable.
> 
> I took down the install pics last year, but will post some at mobile sound science when I revamp my install the next couple months.



Yep.....I am getting excited about doing mine. Right now...just to see if I could do it.....I time aligned and set a nice curve on the factory system.....and it sounds very nice. Not really loud...but very nice to listen to. I am hoping to fit a 5 1/4 tangband sub in the center location....not sure about the depth yet...but hoping to fit it in. Working on tweeter and aura hid in the pillars....and not sure on the 8" in the doors yet.


ooops...sorry. Hijacking thread...will hush! lol


----------



## IndianScout




----------



## sqshoestring

I don't think a light bulb knows the difference between AC or DC power.

Its power under the curve that increases with clipping, or average power.

It sure looks like DC on a scope, for a moment lol. But it does not really matter power is power, which makes the heat, more power is more heat.

Subs don't hang on a clip, they hardly notice clipping any normal person would listen to. This thread is getting so messed up.


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## ern2112

Agreed on the light bulb. Since there really is no way to prove or disprove the "hanging"...guess it remains a mystery. Would be cool to look at this at full clip at 20hz.....through high speed camera.


----------



## trumpet

ern2112 said:


> Agreed on the light bulb. Since there really is no way to prove or disprove the "hanging"...guess it remains a mystery. Would be cool to look at this at full clip at 20hz.....through high speed camera.


It's been explained in detail in a different thread as to why the cone does not "hang" for any appreciable time during hard clipping.
http://www.diymobileaudio.com/forum/general-car-audio-discussion/87065-underpowering-sub.html


----------



## MarkZ

ern2112 said:


> Agreed on the light bulb. Since there really is no way to prove or disprove the "hanging"...guess it remains a mystery. Would be cool to look at this at full clip at 20hz.....through high speed camera.


You don't have to look at it. You just have to model it. A speaker manufacturer knows EXACTLY what the cone movement is going to look like before they build the speaker. There's no mystery.


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## ern2112

:thumbsup:


----------



## IndianScout

I don't get the whole argument and links posted, will a 500w sub work at 100w, of course it will, while we all spec out our systems so they are matched to handle the power provided to them, we put our setting at 75-80% or the knee of the amp, but unless you listen to your system at full blast why would the sub not work at say 30w, sure it will.

if you're going into the clipping mode, you need to rethink how you set your system up and how to tune it..




> 2. Black discolouration at one end of the voice coil.
> This is also a common sight and indicates either the voice coil was not centred during manufacture OR that the damage was caused by DC current rather than audio frequency current. A large DC current will displace the voice coil to one or other extreme. A faulty amplifier is automatically suspected.


link..


----------



## MarkZ

IndianScout said:


> link..


DC in this context doesn't mean clipping, it means that DC was literally applied to the speaker. This isn't uncommon for certain amplifiers to fail in this way.


----------



## P-EAZY

ern2112 said:


> Power does not blow speakers..it never has and never will..heat does. When a sign wave is clipped, it causes the speaker to "hang" for a time at the top of the wave and at the bottom....and during that time its like putting a battery on the speaker terminals. Giving enough time and heat....the voice coil will blow.


That's the most ridiculous thing I've heard in this entire thread. Power doesent blow speakers? Yes a badly clipped signal will damage a speaker, but only with enough power. And I can assure you that any speaker can be blown with a perfect sin wave if you give it enough power. Once you exceed the mechanical limit of a speaker it is blown. Try putting a thousand watt amp on a speaker rated for 25 watts. You dont have to give it a clipped signal to say goodbye to that speaker.


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## TurboTR

DC doesn't have to be a flat line. It can/does have ripple on it as well (eg a DC-DC converter output with ripple voltage). It just doesn't change polarity/direction. Simply put, Direct Current (only + or only -) vs Alternating +/- Current.

That's why the Fluke didn't measure DC; the clipping waveform must have been ~ symmetrical positive and negative which is AC with avg DC value of 0v. Clipping doesn't have to be symmetric though.

When the wave clips and goes square the RMS power goes up significantly:

From the www:
Square wave: Vrms = Vpk
Sine wave: Vrms ~= 0.707*Vpk

Personally I tend to agree too, applying a steady state current (at the flat tops) does tend to park the cone. Just like taking a small battery across the speaker (to test the speaker polarity) makes the cone stick out (or draw in) and hold there as long as the steady voltage is applied. No cap inline of course, which blocks DC.


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## MarkZ

TurboTR said:


> Personally I tend to agree too, applying a steady state current (at the flat tops) does tend to park the cone. Just like taking a small battery across the speaker (to test the speaker polarity) makes the cone stick out (or draw in) and hold there as long as the steady voltage is applied. No cap inline of course, which blocks DC.


Placing a battery on the speaker and clipping an AC signal are two entirely different things. If you can place the battery on your speaker and remove it all within a few milliseconds, then you can compare the two. And if you keep the capacitor there, the cone _will_ move under these conditions (hence, AC).

And to complete the analogy, if you repeat the process of placing the battery on the terminals and removing it a few milliseconds later -- and do this repeatedly -- then you're mimicking what happens when you put a square wave on the speaker. This, by the way, is AC. Even though it's coming from a DC source (your battery).

This is also exactly how DC-AC converters (e.g. switchmode power supplies) work.


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## gstokes

alm001 said:


> An oscillating square wave is not DC.


^^^^, real men of genius :thumbsup:


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