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In Reply to: C'mon, neo ... posted by andyr on October 13, 2006 at 14:52:13:
I worked until 2am Thursday night and I tried to get away with a quickie answer since I was feelin' kinda lazy. Then when I saw your post I got motivated to give a more complete answer but then the wife decided it was time to go out for dinner and I had to leave the post sitting on the computer until this afternoon.
I got the same xo points as you did (150 Hz and 1600 Hz) and here are the plots:
I find it interesting that Magnepan tends to use 2nd order filters but they set the Q < 1/2 so it behaves more like a first order but with 2nd order phase relationships.
I may be an egoist but at least I don't talk about other people.
Follow Ups:
Yes, I've also wondered why they nearly always have them "flatter" than 12 or 18dB?Regards,
Soooo... are you saying that the actual high pass crossover point if you were using an active crossover would be 1600hz cutoff with a 12db slope?
as the LP & HP curves intersect at a certain frequency (which I reckon should be called the "crossover point") yet neither the -3dB point of the 20.1 mid LP nor the ribbon HP is 1600Hz (they are spread apart a bit). The -3dB frequency is commonly used to define a "crossover".And whether you are using an active crossover or a passive, the maths is the same!
If you are planning on going 3-way active with your 20.1s, I could suggest some good HP & LP "crossover frequencies" to try (with the help of lspCAD). If you'd like to email me direct, I can send you some plots from lspCAD which show the stock crossover response and also a suggested mod which I believe would make them sound better (at least, the same kind of mod to my IIIAs has made THEM sound better!! :-)) ).
Regards,
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