At 10:12 AM 1/28/2000 -0500, you wrote:
>Further, being that the sound may be reproduced by a round speaker it
>travels out ward as a cone expanding .::::: Your ear only picks up a small
>portion of that cone but it doesn't matter because it is only going to
>interpret the wave speed and oscillation frequency inorder to identify the
>sound and its volume.
>
>Mike
>98 Ram quad cab 318
>K&N,Gibson duals,180 stant
>285/55 18s
>JL audio stealth box
Very true, but you have to factor in which cone shape reproduces the
original sounds the most accurately. The cone shape and size determines
what frequencies can be produced by the speaker. You can't get perfect
bass reproduction (20Hz to 150Hz as an example) from a 6" or smaller
speaker. The lower the bass frequency, the larger the speaker cone has to
be to produce the sound waves. Only your larger speakers are rated down to
20Hz. On the other end of the scale, the higher the frequency, the small
the cone has to be. The cone has to vibrate fast enough to produce higher
frequency sounds waves. Normal human hearing is 20Hz to 20KHz, but there
are some that can hear up to 30KHz. That is why tweeters are so small.
Now in car audio, your not expect to get full audio spectrum reproduction
with a basic setup.. That is why they make a wide range of speaker sizes
and shapes. Most oval and irregular shaped speakers are full-range
speakers. They start around 150Hz or so and go to 18KHz at best with the
help of built in (either coaxial/triaxial, or 2 way/3 way) midrange speaker
and tweeters, to get a wide spectrum.
Back to the original question. If you input a clean sine wave signal (from
a frequency generator) in steps of 150Hz, 1KHz, 15KHz, and 20KHz, you will
not get the same clean signal out of the speaker, depending on it's size
and shape. So speaker size and shape does make a difference, if your
looking for accuracy of the reproduction. But most people don't look at it
that way. They hear the noise and "it sounds good".
One last thing, audio is a frequency that most humans hear from 20Hz to
20KHz. It is a sine wave signal. The modulation of the wave, or in other
words, the length (in time) of a single complete sine wave is the frequency
of that signal. A bass frequency is very long in duration, and a high
(20KHz) is very short, in milliseconds and high end of microseconds. The
speaker cone has to vibrate at the same frequency of the original sound to
reproduce that same sound accurately. That is why we have sub woofers,
woofers, midrange, and tweeters and use crossovers to split up the
frequencies going to each one. If all frequencies were fed to a single
speaker, you would get distortion caused by the cone trying to reproduce
the full spectrum of sound waves. Or if the full spectrum was fed to a
tweeter, it would be damaged because it takes more amplitude to create the
lower frequencies than it does the higher which would damage the device,
and it wouldn't be possible for the speaker to create the lower frequencies
since it's cone is too small.
Mike Schwall
__________________________
mschwall@flash.net
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