HiFi vs. Computer

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Archived from groups: rec.audio.tech (More info?)

On Wed, 08 Jun 2005 14:48:33 GMT, "Tim Martin"
<tim2718281@ntlworld.com> wrote:

>
>"Richard Crowley" <rcrowley7@xprt.net> wrote in message
>news:11ads6hp0chg949@corp.supernews.com...
>
>> Congratulations, you have re-invented the microphone.
>
>I think by "microphone" people normally mean a transducer that converts
>changes in air pressure into electrical signals.

Indeed they do, although some microphones such as ribbons are more
velocity-sensitive.

>It's possible to measure movement without that, and in fact there are
>commercial devices using optical measurement to measure such movements.

Specify some. I'm well aware of such devices on machine tools, but not
in this application.

>Such devices are not generally termed "microphones".

They are, if they are used as sonic transducers. Basically, you have
*no* idea what you're talking about - but that's been obvious for some
time.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

 

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On Wed, 08 Jun 2005 15:57:52 GMT, "Tim Martin"
<tim2718281@ntlworld.com> wrote:

>
><dpierce@cartchunk.org> wrote in message
>news:1118245149.952932.31770@g43g2000cwa.googlegroups.com...
>
>> > I think by "microphone" people normally mean a transducer that converts
>> > changes in air pressure into electrical signals.
>> > It's possible to measure movement without that, and in fact there are
>> > commercial devices using optical measurement to measure such movements.
>>
>> And then the optical signal is converted into an electrical signal.
>> So what's the difference (subtle hint: NONE!)
>
>The lack of need for generating an electrical signal from the movement of
>the air may mean that one can use a detection system with physical
>characteristics different from microphones.

Utter bullshit. If you're using laser interferometry to determine the
position of the diaphragm (as used by Celestion, B&W et al for
measuring speaker diaphragm behaviour), you still have to convert that
information back to an electrical signal at some point. Basically,
you're just creating a vastly overcomplex microphone, which will as a
result have *worse* self-noise than a conventional microphone.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

 

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Tim Martin schreef:
> "Stewart Pinkerton" <patent3@dircon.co.uk> wrote in message
> news:10tba1h8lpuhj674hu1a1v1n7na630d1f7@4ax.com...
>
> > >That's incorrect: analog signals are continuous. Between any two points
> in
> > >time where the analog signal is changing, one can find another point in
> time
> > >where the value of the analog signal differs from its values at either of
> > >the first two points in time.
> >
> > Clearly, you have absolutely *no* understanding of the real physical
> > world. Go learn about uncertainty, before you spout such nonsense
> > here.
>
> As usual, instead of commenting on the point made, you put up a smokescreen.
>
> However, if you think what I said is incorrect, please show it. In the case
> of the bird singing in the woods, demonstrate there are two points in
> time,where the analog signal in the interval between those two ponts in time
> is unchanging.
>
> Tim

Tim,

I added this above but I'll repeat it because it may make this clear;
aside from Nyquist, bits etc which I don't understand much of either.

Any sound must be produced mechanically because something must push
molecules into movement. Anything with mass cannot accellerate
infinitely fast. You must know this; "objects at rest tend to stay at
rest . . ." So it is impossible to have an infinite bandwidth soundwave
purely because it could never be produced mechanically. A birds cloaca,
or whatever it uses, has a HF limit where you can't accelerate its mass
fast enough back and forth and thus the HF response has a very definite
limit. On top of that, even the mass of molecules moving back and forth
in a sound wave are limited in the same way.

 

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Tim Martin wrote:
> <dpierce@cartchunk.org> wrote in message
> news:1118263580.233046.252730@g47g2000cwa.googlegroups.com...
>
> > What one CAN say, most definitely, is that the number of possible paths
> > the signal CAN take between the two points is limited by the interval
> > between those two points and the bandwidth of the signal. Make the
> > bandwidth narrow enough, or make the two points close enough, and the
> > signal is uniquely constrained. At that point, then, if you "sample"
> > the signal at those intervals, you can have complete knowledge of the
> > signal wihout having INFINITE knowledge of the signal.
>
> Great, a comment with some substance.
>
> OK, let's suppose our signal is a 1kHz sine wave, followed by a period of
> silence, followed by a 1kHz sine wave. The amplitude of the sine wave is
> the minimum that can be represented in our digital scheme. And let's
> suppose our sampling rate is 50000 times a second .... that is, one sample
> every 20 microseconds..
>
> Now, I think that an analog signal with a silence of 200 microseconds will
> result in the same digital representation as an analog signal with a silence
> of 201 microseconds.

Wrong, because the signal you describe CANNOT be represented in a
system with finite bandwidth, a fundamental principle you abjectly
refuse to grasp. More importantly, you've described a signal that
you cannot even create in the real universe.

Only unless you are willing to say that you have a signal produced
in a "system" whose bandwidth is such (and such <> infinity), that
signal cannot exist in ANY representation, continuous, discrete or
otherwise.

As soon as you come to the realization that the bandwidth MUST be
limited in any realistic signal, you can then have a perfect
discrete sampled representation of that signal.

Your continued unsupportable protests to the contrary, e.g., what
you think, is irrelevant.

 

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"Wessel Dirksen" <wdirksen@gmail.com> wrote in message
news:1118245554.711573.288300@g14g2000cwa.googlegroups.com...

> Simpler yet, infinity is even ruled out by the very vehicle of sound
> propagation itself which can never be infinite. If anything is acoustic
> in nature, it can't be of infinite bandwidth otherwise it would violate
> Newton's basic law of conservation of energy. To say that any "sound"
> has infinite bandwidth is to say that inertia doesn't exist.

Sorry, I don't see why there being no lower limit to time resolution in an
analog signal would violate conservation of energy.

Tim

 

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"Tim Martin" <tim2718281@ntlworld.com> wrote in message
news:4QVpe.7653$8m5.699@newsfe5-gui.ntli.net...
>
> "Wessel Dirksen" <wdirksen@gmail.com> wrote in message
>
news:1118245554.711573.288300@g14g2000cwa.googlegroups.com...
>
> > Simpler yet, infinity is even ruled out by the very
vehicle of sound
> > propagation itself which can never be infinite. If
anything is acoustic
> > in nature, it can't be of infinite bandwidth otherwise
it would violate
> > Newton's basic law of conservation of energy. To say
that any "sound"
> > has infinite bandwidth is to say that inertia doesn't
exist.
>
> Sorry, I don't see why there being no lower limit to time
resolution in an
> analog signal would violate conservation of energy.

A lower limit to time resolution is a consequence of the
signal having finite duration. If the signal went on
indefinitely it would have no lower limit.

If the signal went on indefinitely and had finite energy in
all or most finite time segments, then the total signal
would have infinite amounts energy.

Now if the presence of infinite amounts of energy doesn't in
some sense violate the law of conservation of energy... ;-)

 

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<dpierce@cartchunk.org> wrote in message
news:1118263580.233046.252730@g47g2000cwa.googlegroups.com...

> What one CAN say, most definitely, is that the number of possible paths
> the signal CAN take between the two points is limited by the interval
> between those two points and the bandwidth of the signal. Make the
> bandwidth narrow enough, or make the two points close enough, and the
> signal is uniquely constrained. At that point, then, if you "sample"
> the signal at those intervals, you can have complete knowledge of the
> signal wihout having INFINITE knowledge of the signal.

Great, a comment with some substance.

OK, let's suppose our signal is a 1kHz sine wave, followed by a period of
silence, followed by a 1kHz sine wave. The amplitude of the sine wave is
the minimum that can be represented in our digital scheme. And let's
suppose our sampling rate is 50000 times a second .... that is, one sample
every 20 microseconds..

Now, I think that an analog signal with a silence of 200 microseconds will
result in the same digital representation as an analog signal with a silence
of 201 microseconds.

Do you agree or not?

Tim

 

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Tim Martin wrote:
> <dpierce@cartchunk.org> wrote in message
> news:1118318316.768496.179950@o13g2000cwo.googlegroups.com...
>
> > Wrong, because the signal you describe CANNOT be represented in a
> > system with finite bandwidth, a fundamental principle you abjectly
> > refuse to grasp. More importantly, you've described a signal that
> > you cannot even create in the real universe.
>
> So, you're saying I cannot create a signal comprising a 1kHz sine wave with
> small amplitude, followed by a period of silence, followed by a 1kHz sine
> wave with small amplitude.

No, you're saying that you can.

So, prove us wrong. Produce for us this signal EXACTLY as you have
described it (ignoring the fact, for the moment, that your description
of such signal is QUITE inexact) through any means at your disposal.
By signal, I don't mean an equation (continuous or otherwise), or
a drawing on a piece of paper or any such dodge. I mean a signal.
It can be acoustical, electrical, mechanical, what have you.

By the way, as you HAVE provided a woefully incomplete description,
how about we better define the signal? How long is the 1 kHz
signal? Exactly when does it end? How long is the silence? Exactly
when does it end? How silent is silent? How long is the second period
of the 1 kHz since wave? How small is its amplitude?

Fine, you say it can, so produce it.

Let us know.

 

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On Thu, 09 Jun 2005 11:35:28 GMT, "Tim Martin"
<tim2718281@ntlworld.com> wrote:

>
>"Wessel Dirksen" <wdirksen@gmail.com> wrote in message
>news:1118245554.711573.288300@g14g2000cwa.googlegroups.com...
>
>> Simpler yet, infinity is even ruled out by the very vehicle of sound
>> propagation itself which can never be infinite. If anything is acoustic
>> in nature, it can't be of infinite bandwidth otherwise it would violate
>> Newton's basic law of conservation of energy. To say that any "sound"
>> has infinite bandwidth is to say that inertia doesn't exist.
>
>Sorry, I don't see why there being no lower limit to time resolution in an
>analog signal would violate conservation of energy.

That's because you don't understand the subject. No lower limit to
time resolution = infinite bandwidth = infinite energy.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

 

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<dpierce@cartchunk.org> wrote in message
news:1118318316.768496.179950@o13g2000cwo.googlegroups.com...

> Wrong, because the signal you describe CANNOT be represented in a
> system with finite bandwidth, a fundamental principle you abjectly
> refuse to grasp. More importantly, you've described a signal that
> you cannot even create in the real universe.

So, you're saying I cannot create a signal comprising a 1kHz sine wave with
small amplitude, followed by a period of silence, followed by a 1kHz sine
wave with small amplitude.

Tim

 

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Archived from groups: rec.audio.tech (More info?)

"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:L-2dnVo0xeD_ozXfRVn-sg@comcast.com...
> If the signal went on indefinitely and had finite energy in
> all or most finite time segments, then the total signal
> would have infinite amounts energy.
>
> Now if the presence of infinite amounts of energy doesn't in
> some sense violate the law of conservation of energy... ;-)

Of course the duration cannot be infinite, ie. longer than the universe
existence.

MrT.

 

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On Thu, 09 Jun 2005 16:08:47 GMT, "Tim Martin"
<tim2718281@ntlworld.com> wrote:

>
><dpierce@cartchunk.org> wrote in message
>news:1118318316.768496.179950@o13g2000cwo.googlegroups.com...
>
>> Wrong, because the signal you describe CANNOT be represented in a
>> system with finite bandwidth, a fundamental principle you abjectly
>> refuse to grasp. More importantly, you've described a signal that
>> you cannot even create in the real universe.
>
>So, you're saying I cannot create a signal comprising a 1kHz sine wave with
>small amplitude, followed by a period of silence, followed by a 1kHz sine
>wave with small amplitude.

If you allow the sine wave a finite period of attack and decay, and
the 'silence' to have a noise floor, then of course you can.
Otherwise, no one can.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

 

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On Thu, 09 Jun 2005 11:48:47 GMT, "Tim Martin"
<tim2718281@ntlworld.com> wrote:

>
>OK, let's suppose our signal is a 1kHz sine wave, followed by a period of
>silence, followed by a 1kHz sine wave. The amplitude of the sine wave is
>the minimum that can be represented in our digital scheme. And let's
>suppose our sampling rate is 50000 times a second .... that is, one sample
>every 20 microseconds..
>
>Now, I think that an analog signal with a silence of 200 microseconds will
>result in the same digital representation as an analog signal with a silence
>of 201 microseconds.
>
>Do you agree or not?

No. You're describing an analogue waveform ending towards infinite
bandwidth. It can't exist in analogue or digital represention

(If it COULD, you'd be thanking the digital system for ironing out
such glitches, not complaining about low resolution

 

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On Thu, 09 Jun 2005 16:08:47 GMT, "Tim Martin"
<tim2718281@ntlworld.com> wrote:

>So, you're saying I cannot create a signal comprising a 1kHz sine wave with
>small amplitude, followed by a period of silence, followed by a 1kHz sine
>wave with small amplitude.

Not if you want that period of silence to be as short as we've been
discussing. No you can't. You can describe it as a theoretical
possibility. But, lacking resources tending to the infinite, you
can't create it.

 

[Engineer]

Archived from groups: rec.audio.tech (More info?)

"calmar" <calmar@calmar.ws> wrote in message
news:slrnd9k37v.4ve.calmar@news.calmar.ws...
> Hi,
>
> I'm wondering, how a good computer with a good graphic card + good
> speakers can compare to a good HiFi System?
>
> Since good soundcards can be quite expensive, and that only for the
> card
> itself, I would suspect, that that good computer/soundcard and good
> speaker combo can be as good as a good HiFi System?
>
> So I really don't know much about these things.
>
>
> Thanks for any hints.
>
> calmar

For a long time now I have plugged my various PC sound card outputs
(line level, not speaker output) into the AUX input of "surplus"
stereo receivers (1970's to 80's vintage, around 15 to 25 wpc) and
used whatever "spare" stereo speakers that were around at the time.
The results have been generally good for CD's played on the PC. But
all this stuff is in in the office so I can't do an A-B comparison
with my main system.
Anyway, try it. What can you lose?
Cheers,
Roger