Holy crap! WTF happened to my IDMAX ?????

[Horsemanwill 10+ year member]

i think u broke it lol. just kidding did you give Eric a call already? i know he was waiting for it.

 

[audioholic 5,000+ posts]

So while the BCAE info shows that clipping can destroy a coil when the circumstances are such that amplifier output is closely matched to the coil's thermal dissipation abilities and a clipped signal is present, I can no longer attribute this to DC as my mind was trying to rationalize.

You got it exactly. This is why there is many times a debate over if its "DC" or not. In my mind, its just people trying to simplify a more complex situation. A squared waveform can be said to display *some* attributes consistant with both AC and DC. What people want to call it doesn't really matter, so long as the concept is understood.
Cheers.

 

[Kyle_Keating 10+ year member]

An AC voltage signal with the peaks "clipped" off are sending DC voltage to the coil. At frequencies near the stall mode of the driver where the movement is such that it cannot force enough air over the coil relative to the input power, AC is dangerous enough, let alone DC from clipped output. If the power being applied is below the thermal rating of the coil but very near it, sending DC to the coil from very low frequency waveforms that are clipped for an extended amount of time will indeed cause the coil to reach it's thermal limits. You can have driver failure due to clipping.
Clipping is one of the reasons some people end up baking the tweeter so easily. When the waveform going to the tweeter is severely clipped and harmonics begin to reach the the maximum output potential of the amplifier, it begins to resemble a square wave. Or if you will, AC with portions of DC. The tweeter's coil cannot dissipate the heat being generated by the DC voltage from clipped input, not only because the mass of the coil is tiny but also because it's not moving or forcing air over it to cool it. Thus the implementation of Ferrofluid.

It's worth mentioning that complex musical waveforms blending together can also cause DC current to be applied to the coil while operating well within the unclipped power range of the amplifier. DC is the killer.

I don't agree with any of that

A clipped single is simply a square wave. mechanically the driver will not ever do a square wave. Low frequencies are still going to push the driver's cone far and cooling will take place one way or the other. This "DC" stall you are talking about occurs in the voltage waveform, not the driver. Even if it did, it occurs only within one period and the driver still moves up and down each time. The amount it moves depends on how much voltage the amp (clipped or not clipped) and what frequency is being supplied - Because amplifiers don't get clipped constantly and music is not a constant sin wave, the effect of the square wave itself is probably negligible as far as cooling. I would be shocked if it was above the uncertainly threshold for any thermal measurements we can take.

 

[audioholic 5,000+ posts]

I don't agree with any of that
A clipped single is simply a square wave. mechanically the driver will not ever do a square wave. Low frequencies are still going to push the driver's cone far and cooling will take place one way or the other. This "DC" stall you are talking about occurs in the voltage waveform, not the driver. Even if it did, it occurs only within one period and the driver still moves up and down each time. The amount it moves depends on how much voltage the amp (clipped or not clipped) and what frequency is being supplied - Because amplifiers don't get clipped constantly and music is not a constant sin wave, the effect of the square wave itself is probably negligible as far as cooling. I would be shocked if it was above the uncertainly threshold for any thermal measurements we can take.

I believe most of what you mention here has already been covered.
In music, no amplifiers do not get clipped constantly, simply due to the transient nature of the signal. But in a test tone burp type of situation, its very possible.

 

[Kyle_Keating 10+ year member]

edit: not gonna argue anymore, this is a dead horse

 

[DNick454 10+ year member]

edit: not gonna argue anymore, this is a dead horse

Keep beating the dead horse, cuz it aint half as bad off as that IDmax //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif