difference between woofer & subwoofer & tweeter

Those are new names for the fairly old concept of having a bass, mid-range and tweeter type loudspeaker in one box to get a good frequency range from your sound system. The speaker elements are dedicated to a frequency range and designed with that range in mind, of course. The bass elements are typically quite big with large cones (membranes), mid-range use smaller cones and tweeters often have domes rather than cones to create a good coupling to the air. Different technologies and materials are used etc etc.

The signal is filtered so that each element gets the range it is designed for - pushing the full power into a tweeter will probably burn it out pretty quickly, while high-range frequencies will not be heard if pushed into a bass element.

I guess schematics can be found on the net somewhere.

Filters were formerly just coils and capacitors, nowadays digital, active filtering is built into the amplifiers; each speaker may have its own amp and they are all on a digital "bus" of some sort, instead of one amp, speaker cables and filters inside the speaker box.
/RID

Here's a hifi link that should help: http://www.torontohifi.com/view.php?id=15&type=0

look here, please
http://en.wikipedia.org/wiki/Woofer
http://en.wikipedia.org/wiki/Subwoofer
http://en.wikipedia.org/wiki/Tweeter

Sub-Woofer - The Sub-Woofer reproduces extremely low frequencies from about 100 Hz down to 20 Hz. These frequencies are "felt" more than heard. The Sub-Woofer gives the bottom end "beat" to music and the thunderous effects to movie sound tracks. If your sound system is not used for music with a heavy beat or movie sound tracks, then you may not need a Sub-Woofer.

Sub-Woofer may be placed wherever it is convenient since the human ear cannot tell what direction bass sound comes from


Woofer - The Woofer reproduces low frequencies from about 500 Hz down to 100 Hz, the bass sounds. Speaker placement is not critical because Woofers are omnidirectional.


Mirage - The Midrange speaker reproduces midrange frequencies from about 500 Hz to 6000 Hz. The midrange area contains most of the sound for voices and instruments. Speaker placement is more critical because mid-range sound is more directional.


Tweeter - The Tweeter reproduces high frequencies from about 6000 Hz to nearly 20,000 Hz. It is responsible for the brilliance in the sound, mostly associated with harmonics. Speaker placement and angle are critical because high frequency sounds are very directional.

hi jekl2000,
I've read your point carefully ..
 
but the specification of my sub-woofer says that :

Dynamic frequency response from 40Hz-20kHz (20,000 Hz) for a clean range of lows, mids and highs

and u said : The Sub-Woofer reproduces extremely low frequencies from about 100 Hz down to 20 Hz

so can you explain, please ?