I have a question about this circuit snipit:

http://home.lehighone.com/rmetzger/images/Bandpass_Schematic.jpg

I am assuming this is some kind of bandpass filter.

I see that there is both a low-pass and a hi-pass filter which should create a narrow band but I am confused on why this works.

I used the usual passive crossover equation to try to figure out crossover frequencies:

1

Freq = ----------------

2 * Pi * R * C

Where "R" is the value of the crossover impedance resistor and "C" is the value of the capacitor.

The calculated values of the crossover frequencies of the two filters come out to be around 430Hz and 300Hz

This is what I don't understand, To me, the first filter which is a low-pass filter will only allow frequencies BELOW 300Hz through. The second filter with is a high-pass will only let frequencies above 430Hz through. This doesn't make any sense (to me anyway )

Am I just missing something here that has to do with it being coupled with a non-inverting op-amp stage? Please help!

R.G.? Mr. Strand? do you want to take a crack at this one? Many thanx!

-HB