How to calculate series notch filters

[merlin el mago]

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

 

[merlin el mago]

Any help to how to use the calculator?

 

[speakerdoctor]

your calculator link doesn't work for me.

 

[merlin el mago]

For me works

 

[merlin el mago]

mh-audio.nl - Home

 

[speakerdoctor]

I got the link to work. I agree with your results.

 

[merlin el mago]

Any idea why Troels uses other lcr for the woofer Amish revisted

 

[speakerdoctor]

Any idea why Troels uses other lcr for the woofer Amish revisted

Ask troels. He should respond to a question.

 

[merlin el mago]

I chosed well the impedance & the frecuency for each driver?

 

[speakerdoctor]

yes

 

[merlin el mago]

Thanks, I will try

 

[merlin el mago]

Can attached schematic be good for the tweeter?

 

[merlin el mago]

I forgot the tweeter attenuation.

 

[merlin el mago]

I have one doubt: what's the use of notch filter, to cancel peaks or to flat the impedance at the xover frecuency?

 

[speakerdoctor]

More the latter case.

 

[merlin el mago]

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?

 

[giralfino]

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

 

[merlin el mago]

If I cut the tweeter at 2.500Hz why to bother about to flat the impedance at fs 500Hz if it's out of range?

 

[giralfino]

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

 

[merlin el mago]

The tweeter is Seas Excel Millenium T25CF002, the peak is aprox. 7dBs at 600Hz