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snowflake View Drop Down
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    Posted: 30 July 2008 at 1:50pm
Hi
 
I want to add some passive components to some speaker boxes to take out some peaks in the response. I have found some calculators online for getting component values for a resistor, inductor, capacitor in parallel. some of these calculators don't ask you to specify the amount of attenuation and others don't ask the q of the filter you want. can anyone explain the best way of doing this or point me toward a useful website?
 
the other way of doing this would be with damped tubes tuned 1/4 wavelength of the the correct frequency. anyone have experience of doing this? what is a suitable tube diameter? how are q and attenuation level controlled?
 
cheers
Phil
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AndyWave View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AndyWave Quote  Post ReplyReply Direct Link To This Post Posted: 05 August 2008 at 2:06am
So you wanna bite the bullet and design your own x/o?

Wish that was so simple. But no trivial answers here. Basic calculators assume the load being pure resistance. Loudspeaker drivers are usually also inductive and/or capacitive.

Are you going to use them for passive or active system? (x/o-filters and) driver impedance shall change action of notch filters. Specially when frequencies of interest are close to each other.

I usually make a circuit simulation with rough model of driver(at least Re+Le with woofer LP) and possible passive x/o and start with notch component values of textbook example. Then one sees in which direction to change component values. Then make prototype and measure, see if the result fits to reality. Make new1 and see it just gone worse.  make new1 and...(you should already know this if you are to win the battle.)

Leap users tell us your xperiences.

With horn and driver you can try simple series resistor to counteract midband efficiency bump, because efficiency boost will be seen at driver's impedance graph. Also with small bypass cap to bring topend back....
http://www.prodance.cz/protokoly/pd912+cd150+h100.pdf
http://www.prodance.cz/protokoly/2x12mh32+de1050+h6040.pdf

For low frequencies you shouldn't go passive. Be sane person and use parametric eq. For mid in 3way cab, it could be doable without amp-mains-toroid-size coils.

I don't personally recommend more than two or three notches per x/o branch, you start loosing power(+hair+mana. it, perhaps). And it starts to get quite expensive and all is related to everything.

And the evil 2pi is coming to your dreams+glazes your eyes, lost pens and calculators and all, man, everything is at wrong phase in wrong time Wacko.......,3 a.m...groovy....be careful not to end up like meLOLLOLLOL. Thou hath been warned or sumting.

I've never tried the tube option, some discussion maybe at prosounweb, I've seen the thread somewhere.....Danley did use it, some hi-fi used it for prohibiting reflex-tube to transmit mid freqs.

peace, Andy
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