Well, as a fellow EE, I assume you know what a Fourier transform is. So take the Fourier Transform of a square wave and let me know how much DC content is in there.
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Can't blow a speaker by under powering it.......
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Well, as a fellow EE, I assume you know what a Fourier transform is. So take the Fourier Transform of a square wave and let me know how much DC content is in there.
1) Please show me a schematic for an instrument amp that does this.
2) This is completely backwards. A square wave and sine wave share the same lowest frequency component. The square wave has additional high frequency harmonics:
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I can show you one that blew a really nice pair of studio monitors...It was a bit of a murder suicide kinda thing
Indeed. Actually, I used to live in Takoma as well (the DC component). Now I live in Great Falls.
Haha, yes.
bongomania
Commercial User
One time when we "went down this road" FT came up with a fairly interesting web page by a fellow who did some test and measurement and found that by running a sine wave test tone into his power amp, and driving the amp into hard clipping, the wave at the output had an offset of its "center" value. That is, the nominal 0 V point equidistant between + and - peaks was some amount off from the nominal center point before the wave was clipped. And this offset, being an unchanging amount of voltage, could be described as DC.
The problems there include:
1) A bass being played does not put out a sine wave of fixed voltage. It puts out a constantly-changing wave of infinite shapes and peak values.
2) Even if the offset can be called DC, it does not cause a speaker to stop moving, ever. It only means the speaker may be moving centered around a slightly different position than before.
If the speaker stopped, we would not hear a sound. Even in an extreme case, let's say a 40 Hz note played sostenuto, the speaker moves from back to front 40 times a second. The idea that it stops and is "held in place" (causing damage somehow) would mean that in this example, the damage would have to occur in 1/40th of a second. Of course most notes played are higher, and most harmonic content created by distortion is much, MUCH higher frequency, in the KHz range. So the speaker must be "stopping" for less than a thousandth of a second in most cases of clipping. IOW, it is not stopping at all.
The problems there include:
1) A bass being played does not put out a sine wave of fixed voltage. It puts out a constantly-changing wave of infinite shapes and peak values.
2) Even if the offset can be called DC, it does not cause a speaker to stop moving, ever. It only means the speaker may be moving centered around a slightly different position than before.
If the speaker stopped, we would not hear a sound. Even in an extreme case, let's say a 40 Hz note played sostenuto, the speaker moves from back to front 40 times a second. The idea that it stops and is "held in place" (causing damage somehow) would mean that in this example, the damage would have to occur in 1/40th of a second. Of course most notes played are higher, and most harmonic content created by distortion is much, MUCH higher frequency, in the KHz range. So the speaker must be "stopping" for less than a thousandth of a second in most cases of clipping. IOW, it is not stopping at all.
+1
Old moving coil chart recorders could draw square waves. These are essentially the same motor as a speakers.
Even moving coil meters work the same. (if you take off all the buffering and signal processing electronics)
After years of playing and lots of gear changes the only thing I worry about is impedance. I've used powerful amps with weaker speakers and weaker amps with powerful speakers with no ill effects (mind you I don't drive the weak speakers to the point of overdrive). I have long ago given up on matching power ratings on amps and speakers.
edit: phase and impedance that should read
edit: phase and impedance that should read
4th. Have to get mine in there, too
Sorry, Jimmy. As much as I respect most of what you say in this forum, I really did mean after the third post. Once you get THE right answer, there's no need to say any more.
Exactly. Now revisit this:
and translate:
"the speaker system will handle the total power but not the extra power of a square wave"
Well, that doesn't really make much sense.
Or in layman's terms, "overpowering the system".
I really did mean after the third post. Once you get THE right answer, there's no need to say any more.
I thought the question itself was answered fully by the second post. The third was really awesome though, by adding "why the question gets asked" in the first place.
Of course I couldn't possibly be biased at all in that reasoning.
This might help:
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The document doesn't answer the specific question at hand, but offers a way to make a pretty good educated guess:
A conventional speaker is an electromechanical filter. What we hear as flat response is in fact a 12 dB per octave rolloff of cone excursion with increasing frequency above the cone/box resonance. If you've got WinISD you can see this in a typical excursion graph. Thus, a square wave input signal will result in an excursion function where the higher order harmonics are greatly diminished. What we would hear as audible harmonics are actually not very significant in terms of cone motion. For square wave inputs down to 40 or even 30 Hz, it's quite unlikely that any mainstream speaker cone ever grinds to a halt. Thus it's probably a pretty good rule of thumb that the main effect on the speaker is the predicted 1.4x increase in thermal dissipation due to coil heating.
Invalid Link Removed
The document doesn't answer the specific question at hand, but offers a way to make a pretty good educated guess:
A conventional speaker is an electromechanical filter. What we hear as flat response is in fact a 12 dB per octave rolloff of cone excursion with increasing frequency above the cone/box resonance. If you've got WinISD you can see this in a typical excursion graph. Thus, a square wave input signal will result in an excursion function where the higher order harmonics are greatly diminished. What we would hear as audible harmonics are actually not very significant in terms of cone motion. For square wave inputs down to 40 or even 30 Hz, it's quite unlikely that any mainstream speaker cone ever grinds to a halt. Thus it's probably a pretty good rule of thumb that the main effect on the speaker is the predicted 1.4x increase in thermal dissipation due to coil heating.
It doesn't matter how we define terms such as DC. All that matters is what's going on in the speaker.
Admittedly, I'm not an EE, but just a lowly physicist. It's great to be an EE, but what's more important is actually knowing how speakers work.
Admittedly, I'm not an EE, but just a lowly physicist. It's great to be an EE, but what's more important is actually knowing how speakers work.
Bob Lee (QSC)
In case you missed it, I work for QSC Audio!
- Jul 3, 2001
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Fixed it for you.
Almost 90% of the power in a square wave is in the fundamental (1st harmonic).
Bob Lee (QSC)
In case you missed it, I work for QSC Audio!
- Jul 3, 2001
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- Disclosures
- Former Technical Communications Developer, QSC Audio
Actually, the peak of the waveform is where the voice coil will have the most accelerative force. When the waveform reverses polarity (goes from positive to negative or vice-versa), the force will change direction, slowing the VC down and eventually reversing its direction.
The flat top of a clipped waveform, square wave, etc., will simply deliver a constant accelerative force for that extremely short bit of time.
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