How to calculate series notch filters

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merlin el mago

merlin el mago

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Joined 2009
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#1
How to calculate series notch filters for:

Tweeter Seas Millenium T25CF002 & mid-woofer ScanSpeak 18W/8545-00

This calculator mh-audio.nl - Home gives me:

Tweeter 2.500Hz@5R
R 5R
L 1,12mH
C 3,62uF

Woofer 250Hz@6R6
R 6R6
L 11,2mH
C 36,2uF

I used correctly the minimum impedance & frecuency of each driver datasheet?

Attached both datasheets & the tweeter measured in box without xo
 

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  • ScanSpeak 18W-8545-00.pdf
    ScanSpeak 18W-8545-00.pdf
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  • Seas Millenium TCF002.pdf
    Seas Millenium TCF002.pdf
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  • Seas millenium in box without XO.png
    Seas millenium in box without XO.png
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Last edited:
#16
I explaint my case, my tweeter have fs 500Hz I calculate the xo for 2.500Hz so I have to adjust the notch to flat the impedance at this frecuency, other question what impedance have I to use to calculate the notch: nominal impedance or voice coil resistance?
 
#17
If you only need to flatten the impedance on a tweeter after the resonance then you need a Zobel.
IMHO, if you learn to use a proper crossover software (Speaker Workshop or Passive Crossover Designer), you'll realize that Zobels aren't necessary.
A notch needed to eliminate a bump is quite impossible to do right without measurements.
Troels Gravesen uses LCR notches on woofers mainly to eliminate the bump in the midrange (500Hz-1Kz) due to the baffle step effect. I think it is explained on one of the recent designs (Seas Curv perhaps).

Ralf
 
#19
If the tweeter has a strong impedance peak (no ferrofluid for example), and the slope of the crossover is not steep enough, then you have to. Not doing so the tweeter will exhibit a bump at resonance, and that bump will show up in the FR of the speaker, but this could be a sign of a bad design decision.
Ralf
 
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