notch filter info

[R-Carpenter]

Very basic question. Where can I read up on the parallel and series notch filters, how to design and it's effects.
Thanks in advance.

[Ron E]

Parallel notch goes in series with the driver. Used where there is a peak in the passband (where the crossover is not attenuating) of the driver you wish to equalize. It creates a peak in the impedance.

Series notch goes in parallel with the driver - used when the peak is in the stopband of the crossover, especially for woofer and midrange breakup peaks. It can also be used either to mitigate the effects of an impedance peak (in tweeters and midranges) or to mitigate an impedance peak cause by a parallel notch filter that would otherwise mess up the crossover response.

The series notch can also be used in the passband, but it needs an attenuating element between it and the amplifier or it won't work. A series notch causes dips in the impedance when used this way.

Designing the frequency is simple, but the ratio of capacitance to inductance affects the width of the notch.

F = 1/(2*pi*sqrt(L*C)), L in Henries, C in Farads

[Keith Taylor]

You do not say whether you are interested in passive or active notch filters, but by mentioning parallel filters I presume it is the former. If you go to http://www.linkwitzlab.com/filters.htm you will find quite a lot of information on a type of active notch filter that uses a gyrator to simulate inductance. There is also a link to a spreadsheet calculator which allows you to specify centre frequency, notch depth and Q. Even if you are not interested in an active implementation the spreadsheet gives you the L and C values as well as damping resistor value to define the Q. Where it may not suit you is in the circuit source and load impedances should you be working at speaker voice coil impedance.
Keith

[R-Carpenter]

Thanks Ron and Keith.
Passive filters is what interest me.
I know the basics and what I was actually looking for is a big fat book or a study that would describe all the effects including horizontal and vertical response of the speaker in detail.
This world of speaker building is somehow very mysterious. Very little info structured and organized info. I'll keep on looking.
Perhaps a college in NY has a class on crossover circuit design.

[Ron E]

Originally posted by R-Carpenter
Passive filters is what interest me.
I know the basics and what I was actually looking for is a big fat book or a study that would describe all the effects including horizontal and vertical response of the speaker in detail.
This world of speaker building is somehow very mysterious. Very little info structured and organized info. I'll keep on looking.
Perhaps a college in NY has a class on crossover circuit design.

No such book exists. Would there be interest in such a book, do you think? It might be entertaining to write...

I learned what little I know in the course of studying engineering. If you want a full course, look to any of the engineering disciplines. The minimum to be able to churn through such calculations could be taught in a day, but I fear the mindset that goes with it is a little longer in coming.

Look to elementary circuit analysis courses and courses on systems analysis with laplace transforms. Usually these are taught after a full course of calculus and differential equations.

Good luck

[R-Carpenter]

I took this classes about 20 years ago.
But it would be interesting to see a book on advanced crossover designs. May be some day Joe D'Appolito will write it. Well back to work for me.

[Ron E]

Interesting. It almost never fails when answering a question like this that the person asking the question claims to "know that stuff already". Well, "that stuff" is sufficient to design a crossover or analyze a notch filter. The rest is experience, and you can't really teach experience in a "big fat" book.

There are two "skinny" books on loudspeaker design that are more in depth than the usual cookbook.. "Testing Loudspeakers" and "Loudspeaker Recipes". I assume you know how to use google, as well?