Okay, I understand the very basics of speaker operation: the amplifier sends
an AC current at, say, 100hz; this causes the speaker cone to move back and
forth at the same frequency, which creates the "waves" of varying air
pressure that make up sound.

What I can't visualize is how the same speaker can at the same time produce
another tone at 1000hz, let alone all the different sounds in musical
playback. How does it move back and forth at 100hz and simultaneously move
back and forth at 1000hz?

How does one driver produce different sounds at the same time?

Go ahead and use long words. I'll look 'em up.

Okay, I understand the very basics of speaker operation: the amplifier
sends
an AC current at, say, 100hz; this causes the speaker cone to move back
and
forth at the same frequency, which creates the "waves" of varying air
pressure that make up sound.

What I can't visualize is how the same speaker can at the same time
produce
another tone at 1000hz, let alone all the different sounds in musical
playback. How does it move back and forth at 100hz and simultaneously
move
back and forth at 1000hz?

How does one driver produce different sounds at the same time?

Go ahead and use long words. I'll look 'em up.

If you've seen a signal with a lot of frequencies in it up close, you'll
notice that it looks like a squiggle. It often doesn't look like a nice
smooth sine wave. If you were to literally draw a squiggle on a piece of
paper, you could give it to a computer and do a frequency analysis of that
signal. That's how a speaker works. It tries to reproduce that squiggle,
even if it isn't a smooth sine wave.

MZ wrote: "That's how a speaker works. It tries to reproduce that squiggle,
even if it isn't a smooth sine wave."

Yeah, but how does the cone produce more than one sound at different
frequencies at the same time?

Tony



--
Eclipse CD8454 Head Unit, Phoenix Gold ZX475ti, ZX450 and ZX500 Amplifiers,
Phoenix Gold EQ-232 30-Band EQ, Dynaudio System 360 Tri-Amped In Front and
Focal 130HCs For Rear Fill, 2 Soundstream EXACT10s In Aperiodic Enclosure
"MZ" wrote in message
...
Okay, I understand the very basics of speaker operation: the amplifier
sends
an AC current at, say, 100hz; this causes the speaker cone to move back
and
forth at the same frequency, which creates the "waves" of varying air
pressure that make up sound.

What I can't visualize is how the same speaker can at the same time
produce
another tone at 1000hz, let alone all the different sounds in musical
playback. How does it move back and forth at 100hz and simultaneously
move
back and forth at 1000hz?

How does one driver produce different sounds at the same time?

Go ahead and use long words. I'll look 'em up.

If you've seen a signal with a lot of frequencies in it up close, you'll
notice that it looks like a squiggle. It often doesn't look like a nice
smooth sine wave. If you were to literally draw a squiggle on a piece of
paper, you could give it to a computer and do a frequency analysis of that
signal. That's how a speaker works. It tries to reproduce that squiggle,
even if it isn't a smooth sine wave.

"Tony F" wrote in message
...
MZ wrote: "That's how a speaker works. It tries to reproduce that
squiggle, even if it isn't a smooth sine wave."

Yeah, but how does the cone produce more than one sound at different
frequencies at the same time?

Tony


It's not producing more than one sound.. That "squiggle" is a single or
combination of sine waves at different frequencies. If you took two sine
waves and put them on the same axis, one at 100hz and one at 1000 Hz, the
resulting waveform of combining them would be the addition of the two. Then
you get a 1000 Hz sine wave that uses the 100 Hz wave as it's axis. It gets
more complicated as you add in more frequencies but that's the basic gist of
it.

The cone's movement should directly correlate to the wave form.

-Bruce

MZ wrote: "That's how a speaker works. It tries to reproduce that
squiggle,
even if it isn't a smooth sine wave."

Yeah, but how does the cone produce more than one sound at different
frequencies at the same time?

The speaker is also reproducing the squiggle.

Take, for instance, a 100 Hz square wave. We know that a 100 Hz square wave
can also be written as:

sq(100) = sin(100) + 1/3*sin(300) + 1/5*sin(500) + 1/7*sin(700) +
1/9*sin(900) + ...

(the numbers in parenthesis indicate the frequency)

So, a square wave is nothing more than a bunch of sine waves added together.
If you assume that we've got a magical speaker that can accurately reproduce
really high frequencies and that its impedance is flat across the entire
bandwidth, then the speaker will also move in a square wave fashion. In
doing so, it's reproducing 100Hz, 300Hz, 500Hz, 700Hz, and so forth all at
the same time.

It doesn't. Good question though. Same question as how does a record
needle pickup multiple frequencies, or how does a stereo wire handle
multiple frequencies? They don't. In the real world, there is no such
thing as multiple frequencies. When a sound occurs in the air (the only
place sound can occur, other than water, etc.) it's a single pressure
wave.
If 2 instruments are playing at once, or 2 keys on the piano are played at
once, these get combined into a single wave that is neither 1000 Hz nor
100
Hz, for example.

Well, no, they're not pure sine waves, but they are still 1000 Hz and 100 Hz
(to be precise, 100 Hz plus 1000 Hz). In the real world, there IS such a
thing as multiple frequencies.

"MZ" wrote in message
...

Well, no, they're not pure sine waves, but they are still 1000 Hz and 100
Hz
(to be precise, 100 Hz plus 1000 Hz). In the real world, there IS such a
thing as multiple frequencies.

Not individually. Of course there are multiple frequencies, but they are
blended together. It's kind of like mixing red and yellow and getting
orange. Yes, there are multiple colors, but you don't see separate colors.
You just see one color. The color white has all colors of the rainbow and
you can break it down into individual colors, but that's not how your eye
sees it. When sounds get mixed together, the ear hears only a single unique
pressure wave. In some cases the end result can even be nothing - if you
get 2 sounds of the same frequency exactly out of phase, you'll hear
nothing.

Well, no, they're not pure sine waves, but they are still 1000 Hz and
100
Hz
(to be precise, 100 Hz plus 1000 Hz). In the real world, there IS such
a
thing as multiple frequencies.

Not individually. Of course there are multiple frequencies, but they are
blended together. It's kind of like mixing red and yellow and getting
orange. Yes, there are multiple colors, but you don't see separate
colors.
You just see one color. The color white has all colors of the rainbow and
you can break it down into individual colors, but that's not how your eye
sees it. When sounds get mixed together, the ear hears only a single
unique
pressure wave. In some cases the end result can even be nothing - if you
get 2 sounds of the same frequency exactly out of phase, you'll hear
nothing.

The spectral content of a wave is an inherent property of the signal. It's
as intrinsic as 2+2 = 4. What I mean by that is that any wave can be
represented mathematically. You can draw a wave by hand on a chalkboard,
and I can provide a mathematical function to perfectly describe that wave.
It may have as many components in it as the chalk on the board has atoms,
but it's still an accurate representation of that signal. Of course, it's
not feasible to count atoms and come up with an almost infinite set of
terms, but I'm trying to point out that there is indeed a way to represent
the signal mathematically. Instead, one can derive an estimate that's so
precise that you couldn't tell the difference by eye.

Fourier proved long ago that any signal can be represented by a set of sine
waves. He derived an equation to do it, and I won't bother to reproduce it
here. So, if you know what the voltage of your signal is at every instance
of time, you can plug it into the equation and get the spectral
representation of the waveform. That is, the result of his equation can be
proven mathematically to be exactly identical to the waveform that you fed
it. Only it's in a different sort of number space. Instead of referring to
the waveform as a function of time, you're referring to it as a function of
frequency. It's the same waveform - it's just being described differently.

So this is what I meant when I said that multiple frequencies ARE real.
They're as real as the waveform itself. In fact, it IS the waveform. We're
just describing it in different terms.

PS - It's also worth noting, by the way, that your color example can also be
described by Fourier analysis. If you were to mix red and yellow, you'd
still pull out those frequencies with a photometer. Your visual system
isn't a photometer though. We only have a certain number of neurons in to
process this information, so we only have a certain number of ways that we
can see things. In fact, the human visual system uses only three cones to
sample chromatic information; it then collapses this information down to 2
channels - so it builds the amazing abstraction that we refer to as color
from a simple set of 2 channels.