Basic electronics question

[unknownuser]

I'm trying to understand what the components do that make up a crossover when placed in parallel to the driver.

Or let me put it this way..

I know that a cap placed in series to a tweeter will attenuate low frequencies at a given point. And if an inductor is added in parallel to make a second order x-over the low frequencies will be attenuated at a steeper rate. But how? How does an inductor attenuate the lower frequencies? Or for that matter how does the cap in a second order low-pass attenuate the the high frequencies?



(Originally posted by: CB)

[thylantyr]

google reactance

[victor]

> google reactance

so it has to do with reactance? I have always wondered that myself too. I always kind of assumed it works on a low pass because of the inductor being a coil. Seems like that would increase the power to the low end. I actually never even knew that inductors were used on high pass circuits until a few years ago when I had a pair of DLK 3 ways and seen the x-overs were made that way. Seems most commercially available speakers use only a cap for the high pass.

[tedwilt]

> low frequencies will be attenuated at a
> steeper rate. But how? How does an inductor
> attenuate the lower frequencies? Or for that
> matter how does the cap in a second order
> low-pass attenuate the the high frequencies?

Here is how I think about it. Capacitors look like a short circuit (zero resistance) to high frequencies and inductors look like a short circuit to low frequencies. The parallel inductor in the tweeter crossover offers an easier path to the low frequencies than the tweeter.

[thylantyr]

>>so it has to do with reactance?

I guess the simple way to see this is to think
of it as a variable voltage divider network to
attenuate the signal based on frequency.

There is no other magic, capacitors in AC
have capacitive reactance and inductors have
inductive reactance. No rabbits in the hat.

[unknownuser]

> Here is how I think about it. Capacitors
> look like a short circuit (zero resistance)
> to high frequencies and inductors look like
> a short circuit to low frequencies. The
> parallel inductor in the tweeter crossover
> offers an easier path to the low frequencies
> than the tweeter.

Thank you Ted. Your post was a HUGE help. I can now "visualize" the circuit much clearer.
But what of resistors? What does the parallel resistor in a L-pad do? How can a L-pad improve the circuit over a single resistor in series?
Thanks again!



(Originally posted by: CB)

[unknownuser]

> I guess the simple way to see this is to
> think
> of it as a variable voltage divider network
> to
> attenuate the signal based on frequency.

> There is no other magic, capacitors in AC
> have capacitive reactance and inductors have
> inductive reactance. No rabbits in the hat.
Thank you. The google search was a big help to me.
Thanks again.



(Originally posted by: CB)

[tedwilt]

> Thank you Ted. Your post was a HUGE help. I
> can now "visualize" the circuit
> much clearer.
> But what of resistors? What does the
> parallel resistor in a L-pad do? How can a
> L-pad improve the circuit over a single
> resistor in series?
> Thanks again!

The purpose is to keep the impedance the same so the crossover point does not move.