# Seriese notch filter

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#### woody

Paid Member
I just bought FE83en and would like to use it above 500hz with a 6/db crossover on an open baffle. But to do this I need to flatten the impedience at FS. So when I plug the FS of 165hz, RE 7.5 ohms, QES 4.06 and QES 1.057 in a seriese notch calculator it calls for : 121.7 uf, 7.65 mh and a RC of 9.45 ohms. Ok but my question is can I use other values for L and C as long as they are in resonance at 165hz. For example could I use 25 uf and 37 mh and a RC of 9.45 ohms or am I stuck using that 121.7uf cap and 7.65 mh inductor.

#### Osvaldo de Banfield

Yes, you can, but the cost will be the attenuation and phase. Any filter LC particularly, need to work over a definite impedance, and it gives some particular values of L (Inductance) and C (Capacitance) according to them. The Resistive part of the filter, is in few words, is to accommodate those reactive elements to the impedances related to it and give determined values of attenuation, or may for part specific of the filter, like a T shunt for example.

#### phase_accurate

Your Q-value would be off because it is not only depending on R but also on the suare root of the L/C ratio.

Regards

Charles

#### woody

Paid Member
Ok I will just parallel a couple of the big mylar caps I have and wind that 7.65 mh inductor.

#### wolf_teeth

Are you reducing level at all of the Fostex to match the woofers? Then just parallel a resistor to the Fostex of about 50-100% of the impedance at Zmax and see if that gets you close enough. Normally this is high enough resistance applied to lower Fs magnitude, without reducing nominal impedance very much.

Later,
Wolf

#### woody

Paid Member
As I read your responce it occures to me that because my driver will need to be attinuated 2 db . So just using the 2 ohm seriese resistor and a 15 ohm resistor in parallel with the fe83es to attinuate it that inpedience rise at fs should be ok to live with.

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