I have forgotten what the governing equation is (more specifically if
the equation involves just "f" or is it "2pi*f"). If I have this 10 mH
inductor lying around, what capacitor should I combine it with to
create a 200 Hz notch circuit? This is for a full-range coax speaker
in a car. I have calculated a value of 63-ish uF for the cap. Am I on
track?

"dangling entity" wrote in message
ps.com...
I have forgotten what the governing equation is (more specifically if
the equation involves just "f" or is it "2pi*f"). If I have this 10 mH
inductor lying around, what capacitor should I combine it with to
create a 200 Hz notch circuit? This is for a full-range coax speaker
in a car. I have calculated a value of 63-ish uF for the cap. Am I on
track?

Yes you are right, at resonance:

F=1/(2*pi*Square root(L*C)

Sorry couldn't find the correct mathamatical symbols.

Works out at 200.5 Hz

Pete

Thanks for postin' in! Time to solder-up...

The filter will also have -3dB points of 120 and 360 Hz -- and because of
the complex load there will be a secondary notch of about -2dB around 50 Hz.


"dangling entity" wrote in message
oups.com...
Thanks for postin' in! Time to solder-up...

Interesting point about the secondary notch. I've never been exposed
to this side of the design. I guess it is good I would be applying
this filter to the upper range speaker rather than the sub.

I take it the primary notch specs you have cited are for a "no
resistor" filter scenario? If I add in a parallel resistor to tweak
the final output, will the -3 dB points change, or does it just affect
the depth of the notch frequency mostly?