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Author Topic: because they only use tweeters?  (Read 3277 times)

Stephen Kirby

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Re: because they only use tweeters?
« Reply #70 on: September 12, 2017, 04:59:29 pm »

So definitionally, I'm with Chris...no way an amp can make 10x rated power.
If you want to call rated power something other than RMS, like program or music power, typically at 1/8 rated rms, then sure, 10x works.
Most amps are spec'd at a given easy frequency like 1kHz and at some percent THD.  Typically fractions of a percent.  Power is the integration of the area under that waveform.  When you try to increase the voltage swing the top of that waveform is constrained by the limits of the amp, but the shape below that broadens out until you have something sorta resembling a square wave.  Now the area under the waveform, where the amp is sourcing current and the driver is dissipating it, becomes much larger.  Thus the "power" is much greater.  Even though the peak voltage hasn't gotten any greater.  At some point, something usually gives.  Either the amp can't continue to deliver that much power (current over the duration of that waveform) or the speaker's voice coil burns out.
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Mark Wilkinson

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Re: because they only use tweeters?
« Reply #71 on: September 12, 2017, 06:52:21 pm »

Most amps are spec'd at a given easy frequency like 1kHz and at some percent THD.  Typically fractions of a percent.  Power is the integration of the area under that waveform.  When you try to increase the voltage swing the top of that waveform is constrained by the limits of the amp, but the shape below that broadens out until you have something sorta resembling a square wave.  Now the area under the waveform, where the amp is sourcing current and the driver is dissipating it, becomes much larger.  Thus the "power" is much greater.  Even though the peak voltage hasn't gotten any greater.  At some point, something usually gives.  Either the amp can't continue to deliver that much power (current over the duration of that waveform) or the speaker's voice coil burns out.

I dunno Stephen, I really think all the crest factor and waveform shape talk over complicates.
 
IMO, simple RMS is the integration of power you mention...it's heating power....whatever the waveform.
So it's all the power the amp can potentially output, .....with music, music clipped, sine, or square...doesn't matter.

And specs tell me clipping generally occurs right on top of that rated power.
So for short term, heck even for near instantaneous term, there's not 10x available...
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John J.R. Bogle

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Re: because they only use tweeters?
« Reply #72 on: September 15, 2017, 01:54:56 am »

Most understand that a clipped sign wave has similar properties to a square wave, but is actually not an actual square wave, because of the ramps being sinusoidal.  Does this hybrid wave have a technical name?
I'd call it a complex wave form. If the "clipping of a sine wave is severe enough, for most practical purposes it's a square wave (not exactly but the distinction can be a fine one). Sometimes there's a tiny spike at the leading edge of a clipped waveform before the total current draw pulls the voltage back down a bit (depends on circuit design).

Whoever mentioned duty cycle should get kudos. that's exactly what happens. A clipped sinusoidal wave has a longer duty cycle at full available voltage/current making the average MORE than RMS which is derived from a sine wave.
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