parallel notch filter help

[kan3]

http://home.new.rr.com/zaph/audio/audio-speaker11.html

ok,
in that article he noted how including the notch filter helped clean up the midrange and provided response graphs

I don't quite understand how he came up with the values for the components....I've looked into PNF and did the formula and still don't get close to what he does...nor do I understand how the graph with the filter(3rd graph from the top) seemed to smooth out over such a wideband(1khz to 10khz)





ok,
in this unfiltered onaxis graph am I right in assuming a -3db point at 1200hz and 3000hz?

maybe another at 10khz and 13khz...can you do multiple PNF?


thanks

[Ron E]

Any inductor and capacitor that resonate at ~2kHz will work to make your notch.

(2*pi*F)^2=1/(L*C)

Example: If you want to use .6mH
C=1/((2*pi*F)^2*L)
C=1/((2*pi*2000)^2*.0006)=10.5e-6 Farads (10.5uF)
You would then have to select a suitable Resistor, probably best done by trial and error but you could calculate a number. - you won't need much of one - a few ohms

If you had a different inductor on hand you do the formula again.

---------------

Notch filters can cause problems with some crossovers, what is the crossover circuit and how close to the xo frequency? Being that you only need a slight notch, it may not cause problems - but you could possibly remove the peak if it is due to tweeter resonance (impedance peak) by putting a series notch in parallel with the tweeter.

BTW, don't try to notch the 10kHz peaks, it would be a waste of time.

[Timn8ter]

Would it help if I told you John says the center frequency for the low diffraction box was 1800?