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In Reply to: RE: Most likely posted by E-Stat on September 19, 2011 at 10:54:01
"Are you under the impression that musical dynamics are visible using single frequency test tones?"
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A single frequency makes it easier to discuss. But if you like, superimpose a 1 kHZ or 10 KHz signal on top of it and look at it on a scope. How is one with "impact" going to differ from one without impact?
Ron
Follow Ups:
A single frequency makes it easier to discuss.
While failing to address relevant audible factors.
How is one with "impact" going to differ from one without impact?
Have you ever experienced Stravinsky's The Firebird live? The Rite of Spring ? Carmina Burana ?
Those sharp spikes in The Firebird represent the explosive dynamics of that piece. It's the kind of music that can startle the crap out of you with the instantaneous transient power of the brass and percussion and raise the hair on your arms. Such requires an analog output stage capable of large, unencumbered voltage swings. Back in the 70s, I had an Audire power amp. It was a pretty decent sounding unit in its day rated at 100 watts per channel and used a pair of 10,000 uF capacitors in the B+. Following the lead of Frank Van Alstine and his "Double Dyna" modification to the Dynaco 400, I added an outboard power supply with an additional 60,000 uF of capacitance. Audible difference? Exactly what I'm referring to - more impact especially in the bass. Like when reproducing a concert bass drum. The same applies to any amplification stage. You'll find the very best sounding gear has enormous power supplies which allows it to retain that explosive - and impactful - dynamic quality you hear with live music.
rw
Yes, I do have Rite of Spring in vinyl. Your graph is interesting, but the time scale (horizontal) is far to compressed to provide any information. To be of value you need to be able to see the wave form of the sub 100 Hz frequencies.
But to cut to the chase a bass guitar, large drum, etc will produce sine waves and harmonics of the fundamental. Because these are just vibrating strings, and membranes they have to follow the well established laws of physics. They do not do square waves or triangles, just sine waves. This is child's play for any amp to produce especially in the bass range, and voltage levels seen in a CD player.
The power amp is another subject, and really not related to a CD player. However, even to produce a 20 kHz tone at 100 watt levels, you only need a very modest slew rate. Typical amps have 10 times what is needed. As far as capacitors increasing output, I would suggest that is a myth in a class AB amp. See the explanation at the link below.
Ron
"But to cut to the chase a bass guitar, large drum, etc will produce sine waves and harmonics of the fundamental. "
Ah... There is the rub, that's totally wrong. Most of the energy and information from these instruments is in the transients, the LF resonances just add some continuity. Listen to a bass run from an electric bass, now play the same run on your synthesizer using just a single fundamental and you will see what I mean. Even there you are producing transients but their net energy is much lower than the tone.
Transients rule in nature and we are very attuned to them, continuous audible sine waves on the other hand don't exist at all in either nature or the manmade environment. If you think that they do, just expand your time horizon, they are but a convenient simplification.
Regards, Rick
"But to cut to the chase a bass guitar, large drum, etc will produce sine waves and harmonics of the fundamental. "
Ah... There is the rub, that's totally wrong. Most of the energy and information from these instruments is in the transients, the LF resonances just add some continuity. Listen to a bass run from an electric bass, now play the same run on your synthesizer using just a single fundamental and you will see what I mean. Even there you are producing transients but their net energy is much lower than the tone.
Transients rule in nature and we are very attuned to them, continuous audible sine waves on the other hand don't exist at all in either nature or the manmade environment. If you think that they do, just expand your time horizon, they are but a convenient simplification."
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I'm afraid I have to strongly disagree. Of course there is nothing stopping you from playing electronic garbage noise (square waves, triangles, etc) through an amplifier. I would not call that music. But, if you play a real guitar for example, the tension in the string, the weight of the string, and the length determine the frequency the string makes. That is how you tune it of course. Once those are set, all you can really do is change the amplitude, by stretching it further from the rest position. More amplitude does not change the frequency. The velocity of the string still has to start at zero, accelerate, then slow down to a stop, and then accelerate back. If you plot the distance from a fixed point it executes a sine wave on the time base.
And if you call that first movement of the string a transient, it does not go any faster than the laws of physics allow. It is just like a pendulum on a clock. No matter where you start the pendulum it follows the same path, and at the same frequency. That is why the clock keeps time.
The only thing that changes is the amplitude, but not the shape, or frequency. That is why it is so easy to calculate the required slew rate of an amp. It only depends on frequency and amplitude. We can't hear past 20 kHz, so that fixes max frequency. All that is left is amplitude or in electrical terms voltage. Voltage is low in a CD so slew rate required is very modest.
The thing to keep in mind is the pendulum on a clock. Once you let the pendulum go, there isn't a darn thing you can do to make it go any faster or slower. It will go exactly as the spring mass laws of physics say it will -- in a a perfect sine wave pattern. A guitar string is the same, the skin on a drum is the same. Wind instruments behave the same using air compression as the spring, and tube length with air as the mass. Damping really does not change anything either. The frequency remains the same. The amplitude just reduces faster as damping goes up.
Ron
"I'm afraid I have to strongly disagree."
Excellent, you've provided the basis for a good discussion!
"Of course there is nothing stopping you from playing electronic garbage noise (squarewaves, triangles, etc) through an amplifier. I would not call that music."
Well, no there isn't, but I specified sine waves, the very thing that you believe instruments produce.
"But, if you play a real guitar for example, the tension in the string, the weight of the string, and the length determine the frequency the string makes. That is how you tune it of course. Once those are set, all you can really do is change the amplitude, by stretching it further from the rest position. More amplitude does not change the frequency. The velocity of the string still has to start at zero, accelerate, then slow down to a stop, and then accelerate back. If you plot the distance from a fixed point it executes a sine wave on the time base."
If that were the case you would be unable to tell a guitar from a synthesizer playing "sine waves". One listen is worth a kiloword, with a little googling you can find a program that will generate sine waves. Fiddle around the generator and your guitar so that an open string zero beats with the generator and listen to the difference between them. The guitar has a complex, time-varying, harmonic structure that the test tone lacks. This is because it is NOT generating a sine wave.
"And if you call that first movement of the string a transient, it does not go any faster than the laws of physics allow."
Well, I do call it a transient and the laws of physics impose no limit. F=MA and since the mass is constant the acceleration is directly proportional to the applied force for small displacements.
"It is just like a pendulum on a clock. No matter where you start the pendulum it follows the same path, and at the same frequency. That is why the clock keeps time."
I guess you haven't actually played with them. The ideal is to have a very high Q mechanical resonance that is independent of excitation and environment. They are riddled with problems and in case you haven't noticed they aren't used much these days. I can go deeply into their problems and patches if you care (my mother actually used to be in the business of restoring the critters!) but they only approximate 'simple harmonic motion'.
"The only thing that changes is the amplitude, but not the shape, or frequency. That is why it is so easy to calculate the required slew rate of an amp. It only depends on frequency and amplitude. We can't hear past 20 kHz, so that fixes max frequency. All that is left is amplitude or in electrical terms voltage. Voltage is low in a CD so slew rate required is very modest."
Slew rate limitations in audio Amps. can be a serious audible problem for several reasons, the most well known is the generation of odd harmonics due to the slew rate induced lag and loss of GBW degrading the phase margin. The terrors of TIM. (You old enough to remember that acronym?)
"The thing to keep in mind is the pendulum on a clock. Once you let the pendulum go, there isn't a darn thing you can do to make it go any faster or slower. It will go exactly as the spring mass laws of physics say it will -- in a a perfect sine wave pattern."
Clocks again... It will be a 'damped sine wave' as opposed to a real sine wave and will fritter away it's transient energy in air resistance, suspension losses and, in a real clock, friction from the gears and bearings. To compensate for this clocks have escapement mechanisms that dump in a little extra energy each cycle from the spring but of course that introduces even more distortion and lowers the Q to boot.
"A guitar string is the same, the skin on a drum is the same. Wind instruments behave the same using air compression as the spring, and tube length with air as the mass. Damping really does not change anything either. The frequency remains the same. The amplitude just reduces faster as damping goes up."
Nah... damping does affect the frequency, it reduces it. Once you reach critical damping the poles stay on the real axis and there isn't ANY frequency.
Sorry for the run-on response Ron, the point I was hoping to make is that the real-world is pretty complex if you look very closely at it. So much so that we use a lot of simplifying assumptions to not get bogged down. Rules of thumb that save so much time even though they really aren't quite "right". When we design things we try to force as much stuff as possible to "don't cares" by trying to make things we can easily control the dominate factors. And so it goes, but it's good to keep in mind that we use limited models of nature, while nature herself isn't so constrained. If you just put a new nylon string on your guitar and tune it to the same frequency as your old one it won't sound the same, it will have a different harmonic structure and in my opinion, sound better, but require a lot of tuning at first and as it stretches and hardens so do the harmonics. That's nature for you!
Regards, Rick
I'm a retired mechanical engineer. One of my areas of expertise was vibration analysis and balancing of rotating equipment. Yes, if you want to nit pick, nature does not behave in a totally simplified theoretical manner. That is because we are not accounting for every little minor factor like air resistance, material imperfections, magnetic field, Coriolis force, the location of the moon, ...
But, I found early in my career that the only way you can deal with the real world is to break it down into the simplest forms and deal individually with all the ones that are significant. And, there is theory to deal with virtually as much as you can comprehend. And when the human mind starts to get taxed then finite element computer programs can take over all the little elements to model the composite one.
But back to the subject at hand. Once you let go of the guitar string, you lose total control of the motion unless you touch it again. It is well described by force equals mass time acceleration. The specifics are that mass stays constant, but force does not. Just like a spring, it starts out high, reduces to zero, and then goes high again. And yes there is damping, so amplitude will reduce with time, and I still say frequency does not significantly change. And it is essentially a sine wave that is produced. Of course there will be harmonics as the string will almost never vibrate in the fundamental mode only. But it will be dominant. The guitar itself will vibrate if it is acoustic and add more harmonics. That is what gives the distinctive sound, and makes a guitar a guitar.
But in all of this there is no such thing as impact. The guitar sting cannot instantly accelerate to a high velocity and ignore that the sting has mass. It will in fact accelerate almost exactly the same as any other string that is the same length, under the same tension, and with the same weight. And with a little tuning it will be exactly the same. And science will almost perfectly predict what that sine wave frequency will be.
And because it behaves this predictably it is easy to calculate the speed you need to replicate the string movement, sound wave movement, and voltage rise in an amp. And that is all it comes down to in the end, voltage at a point in time. There is only one. Amps do not produce multiple frequencies at the same time. They only generate one (per channel). This is what makes digital possible. You are just measuring voltage level at successive points in time. There is a real limit to how fast the sine wave can be generated, and as always a real limit to how fast it can change and the ear still detect the change. The drum, bone linkage just runs out of bandwidth.
Sorry for the rant, but I think science well defines the generation and reproduction of sound. There are no fifth and sixth dimensions that need to be invented to describe sound. Amplitude and frequency is all there is.
Ron
"But in all of this there is no such thing as impact."
Sure there is. I think that you are just so used to working on systems running 'steady state' that you don't think much about forced response. In musical systems they are a big deal as it's the changes that make the music.
Regards, Rick
is quite different from Rod's graphs and assumptions.
rw
... that you don't have to bother with the rest of the message.
As detached from real-world experience as it gets.
What is really mind-boggling - to disprove all that nonsense, one only needs three things:
- a relatively modest system, capable of demonstrating the differences that "do not exist" in Elliott's world;
- couple of items (CDPs, amps etc.) to compare to each other;
- time to do comparison.
But no - they can't be bothered with that.
I don't know who Rod Elliott is, or his qualifications. However, I do notice that he does not depart from the known principles of electrical engineering. If one wants to be imaginative, that is a bit of a limitation.
Ron
Elliott does seem to be content with middle-of-the-road performance. And there's nothing wrong with that. Just different points of reference. My ears find better results from the products from guys like Nelson Pass, Frank Van Alstine, Luke Manley, etc. :)
rw
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