"The Lizard" wrote in message
...
scott johnson wrote:

Coils are also used in high-pass filters.

Yes, they are. Very good observation. But look at how they are used:
they shunt low frequncies, thereby increasing the slope of the high pass
crossover.

http://www.teamrocs.com/technical/pages/twoway.htm

Do you see how that coil is connected in parallel with the tweeter? The
coil has a lower resistance than the tweeter, so electicial current will
go through it instead of the tweeter. That is, of course, until the
frequency rises to the point where the coild has more resistance than
the tweeter. Electical currents at those frequencies will then go
through the tweeter.

A typical crossover which only uses one element has roughly a 6 db /
Octave filter slope. But adding the opposite element at a value that
provides the same crossover slope provides up to 12 db / octave of
filter slope.



Erm? yes, this is ultra-basic stuff.