im studying for an HNC in electronics at college. I have to design a passive filter for a speaker cabinet that holds a tweeter and woofer. I have to chose 2nd order or up. I chose third order filters for both. including the impedance matching parts for the drivers. Lpad and zobel.

I don't understand the dBs, the attenuation bit and the orders bit. please could someone point me in the direction of a site that explains this. I have read this site on dB and attenuation and filters. I still don't get it. I have to show that I understand what im talking about to get the distinction. I have used online calculators to get the values for the above components. I am reading sites recommended for the zobel circuits.

I know that the crossover point is -3dB and that butterworth has been standard for certain reasons, that Bessel is no good for certain reasons. I don't understand the 6dB/octave part. im guessing that an octave is a set of frequencies. that the octave is probably best used because it is a musical thing. I know that an octave contains eight notes. i have read that it is doubling or halving. im guessin this is why it goes 3dB 6dB 12dB 24dB and 48dB for orders of filters. i don't know what that means though.

does that mean it gets quieter or louder. i know there are drop offs after the cross over, the higher the order the steeper the curve. so 3dB would be gradual and 48dB would "nose dive" making it better than the 3dB. (guessing on that one)

any of this correct at all.

is there a math formula that i could use to help me understand. i have looked. i went to the library and found that the only books that would describe anything like this was car audio books and newns audio hifi handbook. though only limited information is available and no answer to my question.

any help would be appreciated

thanks

all the best, and guess what CHRISTMAS SOON! YAY!!!

simon