Quote:
Originally Posted by
Garidy
Without math to support your claims, I'm sorry, but I cannot be swayed. Much of what you have posted seem to have been composed in hast. It's clear that you haven't carefully read, and re-read every word that I have posted. Harmonics and Fundamentals are just signals, signals that all get pegged to the limit of the Voltage rails output, during their propagation within a clipped portion of the wave... I've said this over and over. Distortion is just another name / adjective to describe the qualities of a part of a waveform, a whole waveform, or even an envelop, etc.. It's just energy, it all gets the same treatment when it's in the throws of clipping, if you will.
We are still at step one:
A VC burns only from exceeding the thermal wattage tolerances. Wattage can be produced by either Pure AC energy delivery, Pure DC energy delivery or a mix of the two. AC and DC are not energies- just the delivery types for electrical energy. Think back to Edison end Tesla, they were both selling Power - Coulombs. They both charged by the Kilo-watt, or some such scale; however, one used DC to deliver their energy and the other used AC. So, to a VC, current is current - it's all just coulombs, DC or AC - just coulombs. When coulomb are directly applied to a circuit the voltage and current are locked in phase, in a steady state of delivery. Because the power delivery is absolutely pure (P) not reactive (Q), and non-varying, it can produce more work than AC of the same Voltage and load, if you will. Now, a VC can only handle so many coulombs, for a given period of time, before it will fail - thermal tolerance overrun. DC is able to transfer more current than an alternating current, of the same Voltage, for a given period. The divide between them is based on the frequency and phase angle of the AC carrier. It can be mathematically calculated. In any event, current applied directly, without any gaps, intervals, pauses etc., will heat up a VC faster than any delivery method that spreads the delivery out, over time, and who's power (P) isn't absolute, but rather determined by subtracting the reactive power Q, produced by the presence of inductance and capacitance (which produces phase angle errors). An equivalent AC Voltage will always contain less potential, to perform work, when all other factors being equal, such as load.
Here's the math, as I understand it. Again.
First question is what’s clipping? There’s actually not a settled answer. Frequent poster around here ArnyK would call it clipping at the point where the total harmonic distortion (THD) versus power curve tilts up - - the knee of the THD vs power curve. Different for every amp, not uncommonly somewhere around .01 percent distortion. On the other hand, Stereophile and its sister publication sound and vision use one percent, typically, as clipping. So for example, at 8 ohms, this Anthem receiver
http://www.soundandvision.com/conten...ver-test-bench shows the knee of the curve right about 95 watts, at 0.007 percent distortion, and hits one percent distortion at 138.2 watts, according to the S&V tests. It hits 2% at about 145 watts and IMO unusually stays right around 2% out to 195 watts. More common to see the distortion curve either keep the same slope or become steeper as power increases, and others would have to opine as to what design gives the kind of result shown there (which is, BTW, beside the point).
On the other hand, AIUI, it’s not unusual for musical instrument amplifiers to be specified at a whopping-ish 10% distortion. They aren’t subject to FTC power rating rules, so they don’t often even state the THD at which power is rated in their specs.
Anyway, here’s the math of it. Let’s imagine 4 different amps. The first hits 100 watts at .001 percent distortion, the second hits 100 watts at 1 percent distortion, the third hits 100 watts at 10 percent distortion and the fourth exhibits 20 percent distortion at 100 watts.
1. at .01 percent distortion, the distortion products are, by definition, 80 dB below the fundamental, undistorted signal. Here’s a nice calculator for this
http://www.sengpielaudio.com/calculator-thd.htm.
2. at 1.0% distortion, the distortion is 40 dB below the undistorted signal (using the same calculator)
3. at 10% distortion, the distortion is 20 dB below the undistorted signal (again, same calculator)
4. at 20% distortion, the distortion products lie a mere 13.979 dB below the undistorted signal.
From a power perspective, every 10 dB is a power factor of ten. This page has a handy table, although you’d have to interpolate a lot, if you scroll down a bit . . . called a dB to ratio conversion table
http://www.rapidtables.com/electric/decibel.htm and it’s perfectly obvious that every minus ten dB yields an additional power factor of 1/10. So amp 1, at 100 watts and .001 % distortion, includes roughly .000001 watts of power in the distortion part of the wave form (that’s 0.00000001 times 100 watts). Amp 2, at 1% distortion, includes distortion products in the range of .01 watts (0.0001 times 100 watts). Amp 3, at 10 percent distortion, would have roughly one watt of power in the distortion portion of the waveform (.01 times 100). For amp 4 I’ll round up to 13 dB just because it’s easier math (3 dB is a fifty percent power factor-see the table), so you end up with 100 watts times .05 or 5 watts in the distortion part of the waveform.
See? If the hundred watts would cook a particular speaker, even at 20% distortion, the chances that it’s the extra five watts that really do the deed are just not that strong, IMO. And, from my general reading, in music reproduction , that one percent THD level is about where the distortion becomes noticeable with at least some normal content to at least some people. Distortion twenty times higher, like amp 4, will surely be generating significant ugliness, sonically, even though the distortion is a relatively small part of the power.
Of course, in any single real word amp, THD increases with power. For example, here’s a Bryston.
http://www.soundandvision.com/conten...-labs-measures. At 8 ohms we see the knee of the THD versus power curve at a little over 95 watts and .001% THD. 0.1 percent distortion arrives at 133.2 watts, where the distortion lies 60 dB below the signal, or about .0001332 (.000001 times 133.2) watts will constitute distortion, and 1% distortion arrives at 151.3 watts, where .01513 watts of the power will be distortion, roughly (.0001 times 151.3). We can see 10 percent distortion at about 190 watts, where the distortion will constitute about 9.5 of those watts.
If enough of those "extra" 9.5 watts are above the crossover in a speaker that's already close to trouble, you could kill a speaker with the total power. It's still total power and the tweeter just doesn't give a flying freak whether the power is from added harmonics of clipping, cleanly delivered power for a clean sine wave, added harmonics from violin bowing techniques, or distortion because Terry Kath plugged the power output of one guitar amp into the input of a second guitar amp to achieve massive distortion . . . . In the end, its' the power.